BULLETIN 
25 


Texas 
Memorial 
Museum 


Stratigraphic 
Occurrence 
and 
Correlation 
of 
Early 
Tertiary 
Vertebrate 
Faunas 
Trans-Pecos 
Texas 


Part 
I: 
Vieja 
Area 


By 
John 
Andrew 
Wilson 


AcceptedforPublication 
December5, 
1977 


THE 
TEXAS 
MEMORIAL 
MUSEUM 
2400 
Trinity, 
Austin, 
Texas 
78705 



CONTENTS 


ABSTRACT 
1 
INTRODUCTION 
1 
Acknowledgments 
3 
Previous 
Paleontological 
Work 
6 
Regional 
Geologic 
Setting 
6 
Laramide 
Structures 
7 
Volcanic 
Activity 
7 
Basin 
and 
Range 
Faulting 
7 
VIEJA 
AREA 
7 
Geologic 
Setting 
7 
Biostratigraphy 
Vieja 
Group 
10 
Jeff 
Conglomerate 
10 
Gill 
Breccia 
11 
Colmena 
Formation 
11 
Candelaria 
Local 
Fauna 
13 
Buckshot 
Ignimbrite 
14 
Chambers 
Tuff 
14 
Porvenir 
Local 
Fauna 
18 
Little 
Egypt 
Local 
Fauna 
18 
Capote 
Mountain 
Tuff 
18 
Vieja 
Group 
Undifferentiated 
22 
Ash 
Spring 
Local 
Fauna 
23 
Garren 
Group 
23 
Prietos 
Formation 
23 
Rancho 
Gaitan 
Local 
Fauna 
23 
Chronostratigraphy, 
Vieja 
Group 
23 
Radiochronology 
23 
Biochronology 
24 
Candelaria 
Local 
Fauna 
24 
Porvenir 
Local 
Fauna 
25 
Little 
Egypt 
Local 
Fauna 
30 
Airstrip 
Local 
Fauna 
30 
31

Rancho 
Gaitan 
Local 
Fauna 
31

Paleoenvironment 
Chronostratigraphy 
and 
the 
Chadronian-Uintan 
Boundary 
33 
SUMMARY 
AND 
CONCLUSIONS 
38 
REFERENCES 
39 


III 



ILLUSTRATIONS 


Figure 
Page 


1. 
Index 
map 
of 
Texas 
showing 
location 
of 
principle 
areas 
2 


2. 
Sketch 
map 
of 
volcanic 
centers 
and 
geologic 
quadrangles, 
Trans-Pecos 
Texas 
4 


3. 
Generalized 
stratigraphic 
sections 
with 
approximate 
position 
of 
vertebrate 
faunas 
and 
radiometric 
dated 
samples 
5 


4. 
Index 
to 
Vieja 
area 
8 


5. 
Index 
to 
Vieja 
stratigraphic 
units 
9 


6. 
Colmena 
section 
at 
mouth 
of 
Capote 
Creek 
12 


7. 
Chambers 
section 
at 
Big 
Cliff 
15 


8. 
Chambers 
section 
near 
Adobe 
Springs 
16 


9. 
Chambers 
section 
at 
Reeves 
bonebed 
19 


IV 



TABLES 


Table 
Page 


1. 
Candelaria 
1.f., 
late 
Uintan 
13 


2. 
Distribution 
of 
Candelaria 
l.f. 
in 
Colmena 
Tuff 
13 


3. 
Porvenir 
1.f., 
early 
Chadronian 
20 


4. 
Taxa 
found 
in 
lower 
100 
ft. 
or 
beneath 
lower 
marker 
bed, 
Porvenir 
l.f. 
or 
"Big 
Red 
horizon" 
of 
Patterson 
20 


5. 
Taxa 
found 
at 
"red 
mound," 
Porvenir 
l.f. 
21 


6. 
Taxa 
found 
between 
o—BB 
ft. 
above 
lower 
marker 
bed, 
Porvenir 
l.f. 
or 
"Blue 
Cliff 
horizon" 
of 
Patterson 
21 


7. 
Taxa 
found 
at 
Adobe 
Springs 
area 
21 


8. 
Little 
Egypt 
1.f., 
early 
Chadronian 
21 


9. 
Taxa 
found 
at 
Reeves 
bonebed, 
Little 
Egypt 
l.f 
22 


10. 
Taxa 
found 
at 
Chalk 
Gap 
Draw, 
Little 
Egypt 
l.f 
22 


11. 
Airstrip 
1.f., 
Chadronian 
22 


12. 
Ash 
Spring 
1.f., 
Chadronian 
23 


13. 
Rancho 
Gaitan 
l.f 
24 


14. 
Stratigraphic 
occurrence 
of 
currently 
identified 
taxa 
27 
ff. 


15. 
Distribution 
of 
potassium-argon 
dates 
30 


16. 
Number 
of 
specimens 
of 
medium 
sized 
herbivores, 
Porvenir 
l.f 
31 


V 



STRATIGRAPHIC 
OCCURRENCE 
AND 
CORRELATION 
OF 
EARLY 
TERTIARY 
VERTEBRATE 
FAUNAS 
TRANS-PECOS 
TEXAS 


Part 
I. 
Vieja 
Area 


By 
John 
Andrew 
Wilson* 


ABSTRACT 


Stratigraphic 
positions 
for 
the 
Candelaria 
local 
fauna 
(late 
Uintan), 
the 
Porvenir 
local 
fauna 
(early 
Chadronian), 
Little 
Egypt, 
and 
Airstrip 
local 
faunas 
(Chadronian) 
within 
the 
Vieja 
Group 
are 
given. 
The 
Porvenir 
local 
fauna 
contains 
32 
genera 
in 
common 
with 
Chadronian 
faunas 
to 
the 
north 
and 
six 
generain 
common 
with 
the 
Lapoint 
fauna. 
K-AR 
dates 
of 
approximately 
38 
and 
36 
million 
years 
are 
below 
and 
above 
the 
Porvenir 
local 
fauna. 
A 
mammalian 
assemblage 
sufficientlydistinct 
to 
characterize 
a 
Duchesnean 
age 
is 
not 
present 
in 
the 
Vieja 
area. 
It 
is 
urged 
that 
the 
first 
appearance 
of 
Mesohippus 
mark 
the 
beginning 
of 
the 
Chadronian 
"age." 


INTRODUCTION 


The 
first 
Oligocene 
vertebrate 
fossil 
fauna 
from 
Trans-Pecos 
Texas 
was 
described 
byStovall 
(1948). 
Since 
that 
time 
vertebrate 
faunas 
from 
Paleocene, 
Eocene, 
Oligocene,
and 
Miocene 
have 
been 
collected 
and 
most 
elements 
of 
the 
faunas 
have 
been 
described 
or 
are 
in 
press. 
This 
report 
is 
intended 
to 
bring 
together 
the 
results 
of 
this 
work 
and 
to 
correlate 
the 
Texas 
faunas 
from 
the 
Vieja 


area 
with 
those 
of 
other 
parts 
of 
North 


America. 
This 
biochronologic 
correlation 
is 
supplemented 
by 
radiochronological 
correlation 
where 
possible.

Three 
general 
areas 
within 
Trans-Pecos 
Texas 
have 
produced 
the 
vertebrate 
faunas 
(fig. 
1). 
From 
northwest 
to 
southeast 
these 
are 
(1) 
Sierra 
Vieja 
or 
Rim 
Rock 
Country,

(2) 
a 
critical 
area 
including 
from 
south 
to 
‘Research 
Associate, 
Texas 
Memorial 
Museum, 
Austin;
Professor 
Emeritus, 
Department 
of 
Geological 
Sciences,
The 
University 
of 
Texas 
at 
Austin. 


north, 
the 
Agua 
Fria 
Ranch, 
Bandera 
Mesa 
and 
Coffee 
Cup 
Ranch 
area, 
and 
(3) 
Big 
Bend 


National 
Park. 


The 
Tertiary 
sedimentary 
rocks 
of 
the 
BigBend 
area 
of 
west 
Texas 
were 
the 
last 
in 
the 
state 
to 
be 
divided 
into 
series 
whereas 
the 
subdivisions 
of 
the 
fossiliferous 
Tertiary 
of 
the 
easily 
accessible 
Coastal 
Plain 
were 
known 
by 
the 
turn 
of 
this 
century. 
The 
fossiliferous 
continental 
Pliocene 
deposits 
of 
the 
Panhandle 
were 
known 
by 
the 
1890 
s 
(Cope1893) 
and 
the 
type 
faunas 
for 
the 
Clarendonian 
and 
Hemphillian 
North 
American 
land-mammal 
ages 
were 
established 
by 
the 
19305. 
On 
the 
other 
hand, 
in 
The 
Geologyof 
Texas 
volume 
1, 
Stratigraphy 
(Sellards 
et 
al. 
1933, 
p. 
805), 
known 
as 
"3232," 
and 
the 
last 
summary 
publication 
on 
the 
stratigraphyof 
Texas, 
only 
one 
vertebrate 
fossil 
is 
mentioned 
as 
coming 
from 
Tertiary 
rocks 
of 
Trans-Pecos 
Texas. 
The 
specimen, 
TMM 
41256-4, 
is 
a 
tooth 
of 
Hyracodon, 
an 
Oligocene 
rhinoceros, 
collected 
by 
C. 
L. 
Baker 
and 
identified 
by 
R. 
A. 
Stirton. 
At 
the 
presenttime, 
using 
approximate 
figures, 
there 
are 
known 
28 
genera 
of 
Paleocene 
mammals, 
41 
genera 
of 
Eocene 
mammals, 
55 
genera 
of 
Oligocene 
mammals, 
and 
15 
genera 
of 
Miocene 
mammals. 
In 
addition, 
there 
is 
a 
sizable 
herpetofauna, 
an 
invertebrate 
fauna, 
and 
floras 
that 
have 
not 
been 
studied. 
Except 
for 
two 
collections, 
one 
at 
the 
University 
of 
Oklahoma 
and 
the 
other 
at 
the 
Field 
Museum 
of 
Natural 
History, 
both 
of 
which 
are 
from 
the 
OligoceneChambers 
Tuff 
of 
the 
Vieja 
Group, 
the 
material 
is 
all 
at 
the 
Vertebrate 
PaleontologyLaboratory 
of 
the 
Texas 
Memorial 
Museum,
The 
University 
of 
Texas 
at 
Austin. 


Vertebrate 
fossils 
were 
collected 
in 
the 
early 
1950 
s 
in 
the 
Tertiary 
of 
Big 
Bend 
National 
Park 
in 
connection 
with 
the 
pub


1 



lication 
of 
the 
geologic 
map 
and 
bulletin 
(Maxwell 
et 
al. 
1967) 
on 
the 
geology 
of 
the 
park. 
J. 
H. 
Quinn 
and 
I 
made 
small 
collections 
which 
were 
described 
in 
that 
publication 
(Wilson 
1967) 
in 
order 
to 
document 
the 
presence 
of 
Paleocene 
and 
Eocene 
sediments. 
In 
the 
1960 
s 
my 
attention 
was 
directed 
to 
the 
the 
Vieja 
area 
where 
I 
worked 
in 
conjunctionwith 
the 
mapping 
program 
carried 
on 
by 
Professor 
R. 
K. 
DeFord. 
By 
the 
1970 
s 
the 
Vieja 
country 
had 
become 
less 
productive 
and 
a 
new 
area 
on 
the 
Agua 
Fria 
Quadrangle 
was 


discovered. 


The 
collections 
from 
each 
of 
the 
areas 
have 
been 
treated 
differently. 
The 
Vieja 
collection 
was 
divided 
into 
major 
taxonomic 
groups 
and 
distributed 
to 
experts 
for 
study 
and 
description. 
For 
example, 
rodents 
from 
the 
ViejaGroup 
were 
described 
by 
Albert 
E. 
Wood, 
horses 
by 
Paul 
0. 
McGrew. 
This 
followed 
the 
pattern 
set 
by 
Professor 
Bryan 
Patterson, 
who 
made 
a 
major 
collection 
from 
the 
Chambers 
Tuff 
of 
the 
Vieja 
Group 
for 
the 
Field 
Museum 
of 
Natural 
History. 
In 
contrast 
the 
Paleocene 
fauna 
of 
the 
Black 
Peaks 
Formation 
of 
Big 
Bend 
National 
Park 
was 
treated 
as 
a 
single 
unit 
and 
described 
by 
Schiebout 
(1974). 
There 
are, 
however, 
parts 
of 
all 
faunas 
awaiting 
study. 
In 
addition, 
there 
are 
segments 
of 
the 
stratigraphic 
section 
that 
offer 
promise 
of 
successful 
collecting 
in 
the 
future. 


Volcaniclastic 
rocks 
of 
Trans-Pecos 
Texas 


(figs. 
2,3) 
range 
from 
middle 
Eocene 
to 
Mio


cene 
and 
have 
furnished 
large 
and 
important

collections 
of 
vertebrate 
fossils. 
In 
addition, 


the 
volcanic 
rocks 
provide 
a 
framework 
of 


marker-beds 
which 
serve 
to 
subdivide 
locally

thick 
accumulations 
of 
sediments. 
The 
occur


rence 
together 
of 
the 
fossil 
faunas 
and 
vol


canic 
rocks 
suitable 
for 
radiometric 
dating

makes 
the 
area 
of 
study 
extremely 
important. 


Igneous 
dikes 
intrude 
the 
fossiliferous 
sedi


ment 
and 
are 
suitable 
for 
radiometric 
dating.

They 
furnish 
by 
their 
cross-cutting 
relation


, 


ship, 
minimum 
age 
of 
the 
sediment. 
Radiometric 
dates 
pertinent 
to 
this 
study 
are 
taken 
from 
several 
sources 
and 
are 
given 
in 
table 
15. 


Fig. 
1 
-Map 
of 
Texas 
with 
Presidio 
and 
Brewster 
counties 
shaded. 
Enlarged 
map 
shows 
location 
of 
principle 
fossil


iferous 
areas. 
Big 
Bend 
National 
Park 
shaded. 


The 
late 
Cretaceous 
and 
early 
Tertiary 
sections 
of 
Trans-Pecos 
Texas 
encompass 
the 
Laramide 
interval. 
The 
Tornillo 
Basin 
stratigraphic 
section 
in 
Big 
Bend 
National 
Park, 
as 
given 
by 
Maxwell 
et 
al. 
(1967), 
and 
the 
sequence 
of 
events 
given 
by 
Wilson 
(1972) 
are 
similar 
to 
that 
given 
byTweeto 
(1975) 
for 
the 
southern 
Rocky 
Mountains. 
The 
Tornillo 
Basin 
was 
a 
structural 
basin 
during 
the 
Laramide 
interval 
like 
the 
Raton 
and 
Denver 
Basins 
to 
the 
north 
(Tweeto 
1975, 
fig. 
6). 
The 
Trans-Pecos 
area 
is 
technically 
part 
of 
the 


southern 
Rocky 
Mountains, 
but 
has 
been 
complicated 
by 
later 
volcanic 
activity 
and 
Basin 
and 
Range 
faulting.

This 
report 
is 
divided 
into 
two 
parts. 
Part 
I 
deals 
with 
the 
Sierra 
Vieja 
area; 
Part 
II 
deals 
with 
the 
Agua 
Fria 
area 
and 
will 
be 
publishedlater. 
The 
purpose 
is 
to 
bring 
together 
stratigraphic 
and 
paleontologic 
information 
that 
is 
scattered 
in 
various 
publications 
and 
to 
present 
a 
correlation 
of 
the 
west 
Texas 
faunas 
with 
those 
elsewhere. 
Nothing 
significantly 
new 
can 
be 
added 
to 
the 
early 
Tertiary 
vertebrate 
faunas 
of 
Big 
Bend 
National 
Park 
at 
the 
present 
time. 


Acknowledgments 


The 
major 
financial 
support 
over 
the 
past25 
years 
came 
from 
the 
University 
Research 
Institute 
and 
the 
Geology 
Foundation 
of 
The 
University 
of 
Texas 
at 
Austin. 
The 
National 


Science 
Foundation 
supported 
the 
work, 
in 
part, 
during 
the 
period 
from 
1960-1965 
through 
grants 
G 
13270 
and 
GP 
1058. 
A 
grant, 
NGS 
1439 
(1975), 
was 
received 
from 
the 
National 
Geographic 
Society 
to 
make 
molds 
oftrackways.

It 
is 
impossible 
to 
acknowledge 
individuallyall 
the 
people 
who 
have 
assisted 
me 
in 
this 
project. 
I 
have 
benefited 
from 
discussions 
with 
my 
colleagues 
on 
the 
faculty 
at 
The 
University 
of 
Texas 
at 
Austin, 
S. 
E. 
Clabaugh,

R. 
K. 
DeFord, 
W. 
Langston, 
Jr., 
E. 
L. 
Lundelius, 
Jr., 
F. 
W. 
McDowell, 
and 
W. 
R. 
Muehlberger. 
The 
Albert 
Chambers 
and 
the 
Boyd 
Chambers 
families 
and 
Sheriff 
and 
Mrs. 
Francis 
Rooney 
were 
especially 
hospitable 
during 
our 


3 



Fig. 
2.—Sketch 
map 
of 
Trans-Pecos 
Texas 
and 
adjacent 
Elms 
1949); 
BM, 
Bofecillos 
Mountains 
QuadrangleMexico 
showing 
extent 
of 
extrusive 
igneous 
volcaniclastic 
(McKnight 
1970); 
CM, 
Cathedral 
Mountain 
Quadranglerocks, 
known 
and 
inferred 
volcanic 
centers, 
and 
the 
loca-(McAnulty 
1955); 
JG, 
Jordan 
Gap 
Quadrangle 
(Seward

tion 
of 
geologic 
quadrangles. 
AF, 
Agua 
Fria 
Quadrangle 
1959); 
TM, 
Tascotal 
Mesa 
Quadrangle 
(Erickson 
1953).
(Moon 
1953); 
BH, 
Buck 
Hill 
Quadrangle 
(Goldich 
and 
Modified 
from 
Gorski 
(1970). 


4 



Devils
County.


Hudspeth


HU,

County;


Culberson


CULB,


Park.

NationalFormation


Bend 
Graveyard

Bi9 


part

in

Compiled


report.


this

of 


PartII 


in

described


be 


will 


field

volcanic


Texas


Trans-Pecos


the 


of

sections
stratigraphic


3-Generalized


Fig 


and

scale

to 


not 


are

sections


Wilson,


A.
J. 
by
modified


and 


)

1971


<

Parker


is

F


-

D

lithology


V

b

diagrammatic. 


fossil 
dated 


of

distribution


the

showing
Mexico


Chihuahua,


Prietos,
Cerros


and 


composite


ais 


5Sectionsamples.
dated

potassium-argon


and

collections
vertebrate


in

both

Castolon,


near
is 
6

section


Mountains,


Chisos


and 
Flat

Tornillo


of

section



field 
work 
in 
the 
Vieja 
area. 
To 
other 
ranchers 
who 
generously 
gave 
me 
permission 
to 
enter 
their 
property, 
I 
am 
grateful. 


am 
especially 
grateful 
to 
Margaret 
and 
James 
B. 
Stevens 
for 
their 
unfailing 
physicaland 
scientific 
help 
in 
the 
field 
and 
in 
the 
laboratory.


Anthony 
W. 
Walton 
studied 
the 
sedimentary 
rocks 
of 
the 
Vieja 
area. 
I 
thank 
him 
for 
permission 
to 
use 
information 
from 
his 
dissertation. 
I 
have 
also 
drawn 
from 
the 
theses 
and 
dissertations 
of 
W. 
B. 
Anderson, 
I. 
Ferrusquia-
Villafranca, 
G. 
H. 
Heiken, 
C. 
J. 
Mankin, 
J. 
F. 
McKnight, 
J. 
T. 
Schulenberg, 
and 
P. 
C. 
Twiss. 
Judith 
A. 
Schiebout 
furnished 
me 
information 
on 
the 
tapirs 
and 
rhinos 
she 
is 
currentlystudying, 
and 
similarly 
Eric 
Gustafson 
furnished 
information 
on 
the 
carnivoresthat 
are 
the 
subject 
of 
his 
dissertation. 
Albert 
E. 
Wood 
has 
been 
consulted 
over 
the 
years 
concerning 
the 
rodents 
in 
the 
various 
faunas 
and 
their 
use 
in 
correlation. 
I 
am 
very 
grateful 
to 
him. 
Other 
collaborators 
have 
been 
Craig 
C. 
Black,
Mary 
R. 
Dawson, 
Ann 
Forsten, 
John 
M, 
Harris, 
H. 
0. 
Hofer, 
Paul 
0. 
McGrew, 
Michael 
J. 
Novacek, 
and 
Fred 
Szalay. 
I 
am 
grateful 
to 
Craig 
C. 
Black, 
Mary 
R. 
Dawson, 
and 
Robert 
J. 
Emry 
for 
their 
constructive 
criticism 
of 
the 
manuscript. 
The 
conclusions, 
however, 
are 
my 
own. 


Abbreviations 


CRF 
Cretaceous 
rock 
fragments 
FMNH 
Field 
Museum 
of 
Natural 
History

l. 
local 
fauna 
m. 
million 
yearsOU 
University 
of 
Oklahoma, 
Norman 
TMM 
Texas 
Memorial 
Museum, 
Austin 
VRF 
volcanic 
rock 
fragments 
Previous 
Vertebrate 
Paleontological 
Work 


A 
field 
party 
from 
the 
University 
of 
Oklahoma 
consisting 
of 
W.N. 
MacAnulty, 
D. 
E. 
Savage, 
and 
Wann 
Langston 
made 
the 
first 
collection 
of 
fossil 
vertebrates 
in 
the 
Vieja 
area 
in 
1938; 
in 
1940 
Stovall 
and 
Savage 
returned. 
The 
collection 
was 
described 
by 
Stovall 
(1948). 
A 
second 
and 
larger 
collection 


was 
made 
in 
1946 
by 
Bryan 
Patterson 
and 
James 
H. 
Quinn 
for 
the 
Field 
Museum 
of 
Natural 
History. 
To 
my 
knowledge 
these 
are 
the 
only 
two 
organized 
field 
parties 
that 
had 
the 
express 
intent 
of 
searching 
for 
Tertiary 
vertebrate 
fossils 
in 
the 
Vieja 
area 
prior 
to 


1950. 


Regional 
GeologicSetting 


The 
semi-arid 
climate 
and 
widespread 
outcrops 
make 
Trans-Pecos 
Texas 
one 
of 
the 
most 
interesting 
areas 
for 
geology 
and 
paleontology. 
A 
stratigraphic 
section 
extends 
from 
Precambrian 
to 
Pleistocene. 
The 
section 
has 
been 
folded 
and 
faulted, 
however, 
during 
a 
long 
and 
complex 
history. 
Appalachian 
Mountain 
type 
of 
folding, 
Rocky 
Mountain 
or 
Laramide 
folding 
and 
Basin 
and 
Range 
fault


ing 
all 
intersect 
in 
the 
Big 
Bend 
area. 
In 
addition, 
during 
the 
late 
Eocene 
and 
Oligocenethe 
area 
was 
an 
active 
volcanic 
field. 


The 
youngest 
Cretaceous 
and 
the 
oldest 
Tertiary 
continental 
sediments 
are 
preservedin 
a 
structural 
low 
on 
Tornillo 
Flat 
in 
BigBend 
National 
Park. 
These 
sediments 
are 
debris 
that 
eroded 
from 
the 
eastern 
part 
of 
the 
area 
affected 
by 
the 
Laramide 
Orogeny.
Paleocene 
fluvial 
and 
flood 
plain 
deposits 
lie 
on 
late 
Cretaceous 
sediment 
of 
similar 
origin.
The 
Cretaceous 
sediments 
contain 
a 
reptilianfauna 
now 
attributed 
to 
Maestrichtian 
Age(Lawson 
1976). 
The 
nearest 
similar 
stratigraphic 
sections 
to 
the 
north 
are 
found 
in 
Huerfano 
Park 
and 
the 
Denver 
Basin 
in 
Colorado, 
and 
the 
San 
Juan 
Basin, 
New 
Mexico. 
These 
more 
northerly 
basins, 
however, 
have 
not 
been 
so 
severely 
deformed 
as 
the 
Tornillo 
Basin. 
To 
the 
west, 
Morris 
(1967, 
1968) 
has 
reported 
late 
Cretaceous 
and 
Paleocene 
fossil-
bearing 
sediments 
on 
the 
peninsula 
of 
BajaCalifornia. 
To 
the 
southeast, 
the 
Rio 
Grande 
Embayment, 
and 
to 
the 
south 
the 
Sabinas 
Coal 
Basin 
and 
the 
Parras 
Basin 
all 
contain 
marine 
Paleocene 
sediments 
(Wilson 
1972).

In 
the 
Vieja 
area 
Uintan 
(late 
Eocene) 
and 
Chadronian 
(early 
Oligocene) 
tuffaceous 
sediments 
overlie 
late 
Cretaceous 
continental 
dinosaur-bearing 
rocks 
of 
the 
Picacho 
Fm. 
(Wolleben 
1966). 
In 
the 
Agua 
Fria-Buck 
Hill 


6 



area 
early 
Uintan 
(early 
late 
Eocene) 
sediments 
lie 
on 
the 
Aguja 
Formation 
(Campanian 
(Moon 
1953) 
and 
Boquillas 
Formation 
(Turonian-Santonian). 


Laramide 
Structures.-In 
the 
Big 
Bend 
area, 
structures 
that 
are 
commonly 
dated 
as 
havingbeen 
formed 
during 
the 
Laramide 
Orogeny 
are 
broad 
open 
anticlines 
and 
synclines 
and 
thrust 
faults. 
The 
Del 
Norte 
and 
SantiagoMountains 
to 
the 
north 
and 
northeast 
of 
the 
Tornillo 
Basin 
are 
Laramide 
structures 
(Maxwell 
et 
al. 
1967). 
Cow 
Heaven 
anticline 
and 
Mariscal 
Mt. 
to 
the 
southwest 
and 
south 
are 
also 
Laramide 
structures. 
Other 
Laramide 
folds 
are 
found 
across 
the 
Rio 
Grande 
in 
Coahuila 
(Smith 
1970) 
and 
in 
Chihuahua 
(Gries 
and 
Haenggi 
1972). 
Erosion 
of 
the 
neighboring 
folds 
as 
they 
rose 
must 
have 
furnished 
the 
alluvial 
material 
that 
was 
trapped 
in 
the 
Tornillo 
Basin. 


Paleocene 
and 
early 
Eocene 
sediments 
and 


vertebrates 
have 
been 
found 
in 
a 
small 
area 
in 


the 
Big 
Bend 
National 
Park. 
Three 
localities 


within 
the 
park 
are 
located 
by 
Schiebout 


(1974, 
fig. 
1). 
When 
the 
northern 
part 
of 


Coahuila 
and 
Chihuahua 
are 
more 
thoroughly

explored, 
early 
Tertiary 
sediments 
may 
be 


found 
there 
also. 


Although 
Maxwell 
et 
al. 
(1967, 
p. 
301)

maintain 
that 
the 
lowest 
Tertiary 
rocks 
had 


a 
local 
origin, 
Schiebout 
(1974, 
p. 
8) 
is 
of 


the 
opinion 
that 
some 
of 
the 
sediments 
are 


not 
locally 
derived, 
but 
come 
instead 
from 


the 
west 
or 
northwest. 
This 
would 
certainly

be 
in 
accord 
with 
the 
general 
stratigraphic 
re


lationships 
as 
outlined 
by 
Maxwell 
et 
al. 


(1967, 
p. 
96). 


Volcanic 
Activity—The 
Big 
Bend 
area 
was 
the 
site 
of 
both 
intrusive 
and 
extrusive 
igneous 
activity. 
The 
oldest 
igneous 
rocks 
apparently 
are 
sills 
intruded 
into 
the 
late 
Cretaceous 
Aguja 
and 
Javelina 
Formations 
prior 
to 
the 
time 
of 
Laramide 
folding 
(Maxwell 
et 
al. 
1967). 
Baumgarten 
(pers. 
comm. 
1975) 
has 
traced 
one 
of 
the 
sills 
that 
is 
conformable 
with 
the 
folds 
at 
Maricsal 
Mt. 
and 
Cow 
Heaven 
anticline. 
The 
earliest 
extrusive 
igneousrock 
so 
far 
known 
is 
the 
unnamed 
basalt 
in 


ex-

the 
Canoe 
Formation 
(middle 
Eocene) 


posed 
in 
the 
Crusher 
Section 
1 
and 
2 
(Maxwell 
et 
al. 
1967, 
PI. 
IX) 
in 
Big 
Bend 
National 
Park. 
The 
climax 
of 
the 
igneous 
activity 
was 
during 
the 
early 
Oligocene 
when 
flow 
rock 
and 
ignimbrites 
accumulated 
over 
almost 
the 
entire 
area 
from 
the 
northern 
Davis 
Mountains 
to 
the 
Chisos 
Mountains 
in 
Big 
Bend 
National 
Park. 
By 
the 
Miocene 
most 
of 
the 
extrusive 
activity 
had 
ceased. 
An 
exception 
is 
the 
small 
volcano 
in 
the 
northern 
Vieja 
area 
described 
by 
DeFord 
and 
Bridges 
(1959). 
Dike 
swarms, 
however, 
continued 
to 
intrude 
during 
the 
Miocene 
(Dash 
et 
al. 
1969). 


The 
interbedded 
fossiliferous 
sediments 
and 
volcanic 
flow 
rocks 
give 
the 
opportunity 
to 
correlate 
paleontological 
and 
radiometric 
dates 
from 
middle 
Eocene 
to 
Miocene. 
These 
are 
described 
for 
the 
separate 
areas. 


Basin 
and 
Range 
Fauiting—The 
Big 
Bend 
area 
lies 
on 
the 
eastern 
edge_ 
of 
the 
Basin 
and 
Range 
Province. 
The 
Rim 
Rock 
and 
associat


ed 
faults 
in 
the 
Vieja 
area 
(DeFord 
1958) 
cut 
Chadronian 
sediments 
and 
are 
attributed 
to 
Basin 
and 
Range 
faulting. 
In 
Big 
Bend 
National 
Park 
the 
western 
edge 
of 
the 
Sunken 
Block 
of 
Udden 
(1907) 
is 
bounded 
by 
the 
TerlinguaAbaja 
fault 
zone. 
Some 
of 
the 
faults 
within 
this 
zone 
cut 
Arikareean 
(early 
Miocene) 
sediments 
(Stevens 
1969; 
Stevens 
et 
al. 
1969). 


VIEJA 
AREA 
Geologic 
Setting 


The 
Sierra 
Vieja 
(figs. 
1,4) 
is 
a 
north-
northwest 
trending 
range 
that 
separates 
the 
high 
Davis 
Mountains 
and 
the 
Marfa 
Plateau 
from 
the 
rough 
area 
that 
borders 
the 
Rio 
Grande. 
Although 
it 
is 
only 
10 
to 
15 
miles 
from 
the 
rim 
of 
the 
Sierra 
Vieja 
(also 
called 
the 
Rim 
Rock), 
to 
the 
Rio 
Grande, 
the 
elevation 
drops 
about 
2,000 
feet. 
The 
Vieja 
area 
parallels 
the 
international 
border 
for 
about 
60 
miles 
from 
the 
village 
of 
Candelaria 
on 
the 
south 
to 
the 
Presidio-Jeff 
Davis 
County 
line 
on 
the 
north. 
The 
northern 
part 
of 
the 
area 
is 
drained 
by 
Dieciocho 
(Van 
Horn) 
and 
Quinn 
creeks, 
the 
southern 
part 
by 
CapoteCreek. 
The 
fossiliferous 
areas 
along 
these 


7 



Fig. 
4.—lndex 
map 
to 
sections 
in 
the 
Vieja 
area. 
A. 
Section 
of 
Colmena 
Tuff 
at 
mouth 
of 
CapoteCreek, 
fig. 
6. 
B. 
Section 
of 
Chambers 
Tuff 
at 
Big 
Cliff, 
fig. 
7. 
C. 
Section 
of 
Chambers 
Tuff 
near 
Adobe 
Spring, 
fig. 
8. 
D. 
Section 
of 
Chambers 
Tuff 
at 
Reeves 
Bonebed, 
fig. 
9. 


E. 
Type 
section 
of 
Colmena 
Tuff 
(DeFord 
1958). 
F. 
Type 
section 
of 
Chambers 
Tuff 
(DeFord 
1958). 


G. 
Type 
section 
of 
Capote 
Mt. 
Tuff 
(DeFord 
1958). 
H. 
Ash 
Spring 
locality 
(Harris 
1967a, 
1967b), 
Harris 
and 
Wood 
(1969). 
I. 
Rancho 
Gaitan 
locality 
(Ferrusquia-V. 
1969). 

Fig. 
s.—lndex 
to 
stratigraphic 
units, 
potassium-argon 
dates, 
and 
mammalian 
local 
faunas 
in 
the 
SierraVieja 
or 
Rim 
Rock 


intermittent 
streams 
and 
their 
tributaries 
will 
be 
referred 
to 
as 
northern 
and 
southern 
areas. 


The 
Vieja 
area 
lies 
in 
the 
western 
part 
of 
the 
Davis 
Mountain 
volcanic 
field. 
Several 
centers 
of 
volcanism 
are 
known 
and 
others 
are 
inferred 
(fig. 
2), 
but 
just 
which 
center 
contributed 
which 
particular 
extrusive 
igne


rock 
to 
the 
Vieja 
area 
is 
unknown. 
An

ous 


index 
to 
the 
stratigrpaphic 
succession 
of 
the 
flow 
rocks 
and 
intervening 
tuffs 
and 
tuffaceous 
sediments 
in 
the 
Vieja 
area 
is 
given 
in 
figure 
5, 
together 
with 
the 
potassium-argon 


country. 
Modified 
from 
Walton 
(1972). 
The 
Ford 
Ranch 
bed 
is 
found 
only 
in 
the 
southern 
part 
of 
the 
Vieja 
area 
and 
is 
not 


close 
to 
any 
vertebrate 
localities. 


dates 
and 
the 
approximate 
position 
of 
the 
local 
faunas. 
Volcanic 
activity 
began 
in 
the 
Vieja 
area 
in 
the 
late 
Eocene, 
reached 
a 
peakduring 
the 
early 
Oligocene, 
and 
continued 
at 
least 
to 
the 
Miocene 
(Dash 
et 
al. 
1969).
The 
rim 
of 
the 
Sierra 
Vieja 
is 
formed 
bythe 
major 
scarp 
of 
the 
Rim 
Rock 
Fault 
zone, 
at 
the 
eastern 
edge 
of 
the 
Basin 
and 
RangePhysiographic 
Province. 
Displacement 
alongthe 
Rim 
Rock 
fault 
varies 
from 
900 
to 
3,000feet 
(274-914m) 
(Baker 
1934). 
The 
down-
thrown 
or 
western 
block 
is 
cut 
by 
many 
lesser 
faults 
that 
tilt 
the 
sediments 
and 
flow 
rocks. 


9 



The 
faulting 
repeats 
the 
sequence 
in 
a 
verycomplicated 
manner. 
The 
igneous 
flow 
rocks 
are 
the 
most 
persistent 
marker 
beds 
and 
form 
the 
basis 
for 
mapping. 
In 
addition, 
other 
stratigraphic 
units, 
particularly 
widespreadtuffs, 
have 
been 
found 
that 
are 
reliable 
marker 
beds 
within 
the 
Chambers 
Tuff. 
Fortunately, 
the 
undisturbed 
stratigraphic 
section 
exposed 
along 
the 
fault 
scarp 
of 
the 
Rim 
Rock 
fault 
can 
be 
used 
to 
verify 
the 
superpositionof 
sediments 
and 
volcanic 
flows. 
A 
summaryof 
the 
geologic 
mapping 
and 
stratigraphic 
section 
is 
found 
in 
Twiss 
(1972). 


Biostratigraphy 
Vieja 
Group 


The 
lithologic 
units 
of 
the 
Vieja 
Group 
as 
described 
by 
DeFord 
(1958) 
form 
the 
framework 
of 
this 
section 
of 
the 
report. 
Vertebrate 
fossils 
have 
been 
collected 
at 
various 
places 
from 
some 
of 
the 
lithologic 
units. 
Where 
the 
collections 
were 
considered 
to 
be 
close 
enough 
stratigraphically 
and 
geographically 
they 
were 
grouped 
into 
local 
faunas. 
The 
vertical 
and 
horizontal 
extensions 
of 
the 
volume 
of 
rock 
partly 
occupied 
by 
the 
local 
fauna 
does 
not 
coincide 
with 
and 
is 
not 
to 
be 
interpreted 
as 
coincident 
with 
the 
lithologicunit. 
For 
example, 
the 
Colmena 
Tuff 
is 
a 
lithologic 
unit 
that 
has 
been 
divided 
by 
Walton 
(1972) 
into 
a 
northern 
conglomeratic 
facies 
and 
a 
southern 
volcanic 
rock 
facies. 
The 
southern 
facies 
in 
turn 
can 
be 
subdivided 
into 
a 
lower 
sorted 
facies, 
a 
middle 
lahar 
facies, 
and 
an 
upper 
glass 
facies. 
Fossil 
vertebrates 
have 
been 
found 
only 
in 
the 
southern 
area 
and 
most 
come 
from 
the 
sorted 
facies. 
One 
tooth 
was 
found 
in 
the 
middle 
or 
lahar 
facies 
and 
in 
the 
upper 
glass 
facies 
enough 
taxa 
were 
found 
in 
common 
with 
the 
lower 
facies 
so 
that 
all 
were 
grouped 
together 
in 
the 
Candelaria 
l.f. 


A 
brief 
lithologic 
description 
of 
each 
unit 
or 
marker 
bed 
within 
the 
Vieja 
Group 
is 
given 
for 
purposes 
of 
ease 
of 
field 
identification, 
without 
implying 
that 
the 
lithologic 
unit 
is 
isochronous, 
unless 
so 
stated. 
Attempts 
were 
made 
to 
relate 
vertebrate 
occurrences 
to 
useful 
marker 
beds. 
Three 
such 
beds 
occur 
in 
the 
Chambers 
Tuff 
but 
none 
in 
the 
Capote 


Mountain 
Tuff. 
The 
lithologic 
units 
up 
through 
the 
Chambers 
Tuff 
were 
deposited 
under 
varying 
conditions, 
including 
high 
energy. 
Thicknesses 
vary 
so 
much 
that 
the 
recording 
of 
footage 
was 
felt 
to 
give 
a 
false 
impression 
of 
accuracy. 
This 
is 
particularly 
true 
be-

most 
of 
the 
specimens 
were 
surface 


finds. 
For 
these 
reasons, 
the 
specimens 
are 
related 
to 
igneous 
flow 
rocks 
or 
marker 
beds 
where 
possible, 
and 
then 
grouped 
into 
local 
faunas. 


cause 


Jeff 
Conglomerate 


DeFord 
(1958) 
assigned 
the 
basal 
conglomerate 
of 
the 
Tertiary 
section 
in 
the 
Vieja 
area 
to 
the 
Jeff 
Conglomerate 
of 
the 
Barilla 
Mountains, 
which 
are 
located 
on 
the 
east 
side 
of 
the 
Davis 
Mountains. 
The 
Jeff 
Conglomerate 
in 
the 
Vieja 
area 
was 
deposited 
prior 
to 
the 
volcanic 
activity. 
No 
fossils 
have 
been 
found 
in 
the 
Jeff 
Conglomerate 
either 
in 
the 
Barilla 
Mountains 
(Eifler 
1951) 
or 
the 
Vieja 
area 
(DeFord 
1958) 
or 
the 
Bofecillos 
Mountains 
(McKnight 
1970), 
where 
the 
name 
has 
also 
been 
used. 
A 
variety 
of 
rocks 
of 
several 
different 
ages 
overlie 
the 
Cretaceous 
rocks 
in 
the 
Trans-Pecos 
area. 
For 
instance, 
there 
is 
a 
gradual 
transition 
from 
the 
late 
Cretaceous 
continental 
deposits 
to 
Paleocene 
continental 
deposits 
in 
the 
Tornillo 
Flat 
area 
in 
Big 
Bend 
National 
Park. 
Near 
Castolon 
in 
the 
southern 
part 
of 
the 
park 
the 
Alamo 
Creek 
Basalt 
(lateEocene, 
42.2 
m.y.) 
rests 
directly 
on 
the 
late 
Cretaceous 
Aguja 
Formation. 
In 
the 
Buck 
Hill 
and 
Agua 
Fria 
Quadrangles 
a 
“basal 
Tertiaryconglomerate" 
contains 
an 
early 
late 
Eocene 
(Uintan 
Wagonhound) 
vertebrate 
fauna 
and 
underlies 
a 
tuff 
dated 
45.8 
million 
years 
old. 
On 
Tornillo 
Flat 
where 
the 
stratigraphic 
section 
is 
fuller, 
the 
most 
likely 
correlative 
on 
the 
basis 
of 
lithology 
is 
the 
Big 
Yellow 
Member 
of 
the 
Canoe 
Formation 
(Maxwell 
et 
al. 
1967). 
The 
Big 
Yellow, 
however, 
appears 
to 
be 
middle 
Eocene 
(Bridgerian) 
and 
therefore 
older. 
It 
cannot 
be 
demonstrated 
that 
the 
conglomerates 
at 
the 
base 
of 
the 
various 
Ter


tiary 
sections 
are 
all 
part 
of 
one 
continuous 


body 
of 
rock 
so 
the 
name 
Jeff 
Conglomerate 


as 
applied 
beyond 
the 
Barilla 
Mountains 


10 



and 
the 
northern 
Davis 
Mountains 
should 
be 
used 
with 
caution. 


Gill 
Breccia 


The 
lowest 
volcanic 
rock 
of 
the 
ViejaGroup 
is 
the 
Gill 
Breccia 
(DeFord 
1958). 
It 
has 
the 
maximum 
thickness 
of 
300 
feet 
(91 
m) 
at 
its 
type 
section 
in 
Colmena 
Canyonbut 
thins 
to 
a 
few 
feet 
or 
pinches 
out 
completely 
in 
short 
distances. 
It 
varies 
in 
composition 
but 
in 
the 
vicinity 
of 
the 
mouth 
of 
Capote 
Creek 
it 
is 
a 
"brecciated 
to 
massive,
light 
olive 
green 
to 
dark 
greenish-gray 
fine 
grained 
rock. 
Intimately 
associated 
with 
the 
breccia 
are 
blocks 
of 
Comanchean 
limestone, 
some 
as 
large 
as 
a 
three-story 
building."
(Twiss 
1972, 
p. 
145).

Attempts 
to 
date 
the 
Gill 
by 
potassium-ar 
gon 
resulted 
in 
two 
unsatisfactory 
dates 
of 


75.0 
± 
3.0 
and 
56.5 
± 
3.8 
and 
a 
much 
more 
±

geologically 
reasonable 
date 
of 
40.0 
2. 
The 
evidence 
to 
support 
the 
choice 
of 
the 
latter 
date 
is 
that 
it 
closely 
conforms 
to 
the 
date 
for 
the 
initiation 
of 
volcanic 
activityelsewhere 
in 
the 
west 
Texas 
volcanic 
field. 
Examples 
are 
the 
northern 
Davis 
Mountains 
and 
the 
Barilla 
Mountains 
(Parker 
and 
McDowell 
in 
press), 
the 
Agua 
Fria 
area, 
and 
Big 
Bend 
National 
Park. 


Colmena 
Formation 


The 
Colmena 
Tuff 
is 
the 
lowest 
formation 
in 
the 
Vieja 
Group 
that 
contains 
vertebrate 
fossils 
(fig. 
4, 
secs. 
A, 
E, 
and 
fig. 
6). 
Walton 
(1972), 
in 
the 
most 
recent 
description 
of 
the 
formation, 
divided 
it 
into 
three 
facies. 
The 
one 
that 
outcrops 
in 
the 
northern 
and 
central 
part 
of 
the 
area 
is 
an 
unfossiliferous 
sheet-like 
body 
dominated 
by 
Cretaceous 
calcareous 
rock 
fragments 
(CRF). 
This 
facies 
may 
be, 
in 
part, 
equivalent 
to 
the 
Jeff 
Conglomerate. 
To 
the 
south 
is 
a 
second 
facies 
characterized 
by 
volcanic 
rock 
fragments(VRF), 
and 
it 
is 
from 
this 
body 
of 
rock 
that 
the 
majority 
of 
vertebrate 
fossils 
have 
come, 
therefore, 
only 
this 
VRF 
facies 
will 
be 
treated 
at 
any 
length. 
In 
the 
southern 
area 
the 
VRF 
facies 
is 
overlain 
by 
a 
sparsely 
fossiliferous 


third 
facies 
composed 
mainly 
of 
volcanic 
glass 
shards 
and 
pumice 
fragments. 


Most 
of 
the 
Candelaria 
l.f. 
was 
found 
along 
and 
on 
both 
sides 
of 
the 
mouth 
of 
Capote 
Creek 
in 
the 
southern 
area. 
A 
few 
specimens 
have 
been 
collected 
from 
the 
Colmena 
in 
the 
vicinity 
of 
the 
type 
section 
(DeFord 
1958) 
near 
Nixon 
Falls 
and 
one 
specimen 
about 
one 
mile 
northwest 
of 
the 
Dow 
House. 
No 
individual 
marker 
beds 
could 
be 
found 
within 
the 
Colmena. 
However, 
the 
petrologic 
studies 
of 
Walton 
(1972) 
have 
furnished 
valuable 
information 
on 
the 
facies 
within 
the 
Colmena 
and 
can 
be 
used 
to 
subdivide 
the 
approximately 
250-foot 
(76 
m) 
section 
at 
the 
mouth 
of 
Capote 
Creek. 


The 
Colmena, 
Chambers, 
and 
Capote

Mountain 
were 
designated 
tuffs 
by 
DeFord 


(1958). 
Walton 
(1972) 
refers 
to 
them 
as 
for


mations 
because 
the 
bulk 
of 
each 
consists 
of 


water-laid 
sediment. 
I 
agree 
with 
Walton, 
but 


the 
task 
of 
changing 
the 
names 
on 
diagrams 


and 
tables 
was 
too 
expensive.

The 
following 
is 
a 
summary 
of 
Walton's 
de


scription 
of 
the 
sedimentary 
petrology 
of 
the 


southern 
Colmena 
Tuff 
facies: 


"Sorted 
sandstones 
are 
common 
at 
the 
base 
of 
the 
Colmena. 
An 
excellent 
example 
of 
this 
occurs 
due 
east 
of 
the 
mouth 
of 
Colmena 
Canyon, 
on 
the 
ridge 
that 
forms 
the 
divide 
with 
Panther 
Canyon. 
The 
base 
of 
the 
Colmena 
is 
a 
sorted 
sandstone 
and 
pebbly 
sandstone 
unit 
some 
20 
feet 
thick, 
the 
middle 
of 
the 
formation 
is 
a 
sequence 
of 
massive, 
unsorted 
conglomerates 
about 
200 
feet 
thick 
and 
the 
top 
is 
a 
fine-grained 
unit 
rich 
in 
glassshards, 
about 
25 
feet 
thick. 
A 
similar 
situation 
obtains 
around 
the 
mouth 
of 
CapoteCreek." 
(Walton 
1972, 
p. 
54). 


The 
sorted 
sandstone 
beds 
at 
the 
base 


of 
the 
Colmena 
Tuff 
at 
the 
mouth 
of 
Capote

Creek 
(fig. 
6) 
are 
a 
dull 
red 
brown 
and 
have 


a 
banded 
appearance. 
They 
show 
faint 
cross-

bedding 
and 
lamination, 
and 
Walton 
(1972) 


suggests 
they 
represent 
braided 
stream 
de


posits.

The 
middle 
unit 
of 
the 
VRF 
facies 
of 
the 


Colmena 
is 
interpreted 
as 
being 
a 
succession 


11 



Fig. 6.—Diagramaticsectionof ColmenaTuf at 
the mouth of 
Capote Crek's north 
side. LocationA 
is shownin 
figure 4. Faciesunits 
after Walton 
(1972). Distributionof vertebratefosils
given in table 2.

of 
lahars. 
An 
individual 
unit 
has 
a 
vertical 


size 
gradation 
from 
boulders 
at 
the 
base 
to 
silt 


and 
clay 
at 
the 
top. 
There 
is 
very 
little 
inter


nal 
stratification. 
The 
middle 
200 
feet 
(61 
m)

of 
the 
Colmena 
consists 
of 
these 
kinds 
of 
sedi


ments. 
Fossils 
are 
rare 
in 
this 
part 
of 
the 
sec


tion; 
only 
a 
single 
tooth 
of 
an 
amynodont 
has 


been 
discovered 
and 
it 
was 
within 
the 
lower 


20 
feet 
(7 
m) 
of 
the 
lahar 
facies. 


Walton 
calls 
the 
upper 
facies 
of 
the 
Col


mena 
the 
glass 
facies 
(fig. 
6) 
because 
65 
to 


98 
percent 
of 
the 
framework 
grains 
are 
shards 


and 
pumice. 
The 
informal 
unit, 
"Clabaugh's

bonebed," 
TMM 
40630, 
occurs 
in 
the 
upper 


or 
glass 
facies. 


Volcanic 
activity 
began 
in 
the 
Vieja 
area 
with 
the 
eruption 
of 
the 
Gill 
Breccia. 
A 
whole 
rock 
date 
of 
40.0 
± 
2 
was 
obtained 
froma 
volcanic 
rock 
from 
the 
breccia. 
The 
sorted 
sandstones 
in 
the 
lower 
sedimentary 
unit 
of 
the 
Colmena 
Tuff 
contain 
a 
late 
Eocene 
(UintanMyton) 
fauna. 
The 
date 
of 
40.0 
m.y. 
for 
a 
rock 
underlying 
a 
Myton 
fauna 
is 
perhaps 
a 
little 
too 
young 
when 
compared 
with 
the 
date 


±

41.2 
1.4 
m.y. 
for 
locality 
20 
at 
Badwater, 
Wyoming 
(Black 
1974) 
that 
also 
contains 
a 
Uintan 
fauna, 
A 
date 
of 
39.3 
± 
0.8 
for 
a 
tuff 
at 
the 
contact 
of 
the 
Halfway 
and 
LapointMembers 
of 
the 
Duchesne 
River 
Formation 
(McDowell 
et 
al. 
1973) 
would 
also 
make 
the 


40.0 
date 
for 
the 
Gill 
seem 
young. 
In 
the 
appraisal 
of 
the 
age 
of 
the 
Colmena, 
as 
based 
on 
the 
rodents 
by 
Wood 
(1974), 
the 
Candelaria 
l.f. 
is 
"post-Myton 
in 
age 
but 
probably 
not 
very 
much 
later." 
CandelariaLocalFauna 
Apreliminary 
faunal 
list 
was 
given 
by 
Black 
and 
Dawson 
(1966) 
under 
the 
name 
Colmena 
fauna. 
Taxa 
that 
currently 
comprise 
the 
Candelaria 
l.f. 
and 
their 
stratigraphic 
positions 
are 
given 
in 
tables 
1 
and 
2. 
No 
new 
elements 
have 
been 
added 
to 
the 
Candelaria 
l.f. 
that 
are 
useful 
for 
dating 
since 
the 
papers 
by 
Forsten 
(1971a), 
Wilson 
(1971a, 
1974), 
and 
Wood 
(1974). 
The 
reports 
by 
Gustafson 
on 
the 
carnivores 
and 
Schiebout 
on 
the 
rhinos 
and 
tapiroids 
will 
be 
forthcoming. 
Of 
the 
material 
available 
for 
age 
evaluation, 
Epihippus 
cf. 
gracilis, 
according 
to 
Forsten 
(1971a), 
represents 
a 
southern 
popula-

Table 
1. 
Candelaria 
l.f.*, 
late 
Uintan. 
Dates 
refer 
to 
publica


tions 
and 
are 
listed 
in 
the 
references. 


Taxon 
Reference 


Helix 
leidyi 
Pampe 
1974 


Oreohelix 
grangeri 
Pampe 
1974 


Alligator 
or 
crocodile 
Not 
identified 


Herpetological 
material 
Not 
identified 


PPeratherium 


Omomyid 
gen. 
et 
sp. 
indet 


Manitsha 
johanniculi 
Wood 
1974 


cf. 
eutypomyid 
gen. 
etsp. 
indet. 
Wood 
1974 


Ischryrotomus 
cf. 
/ 
petersoni 
Wood 
1974 


Leptotomus 
leptodus 
Wood 
1974 


Prolapsus 
sp. 
Wood, 
pers. 
com. 
8/75 


Harpagolestes 
sp. 
Gustafson, 
in 
progress 


Epihippus 
cf. 
E. 
gracilis 
Forsten 
1971a 


Sthenodectes 
australis 
Wilson 
1977 


Dilophodon 
n. 
sp. 
Schiebout, 
in 
progress 


Colodon 
cf. 
hancocki 
Schiebout, 
in 
progress 


Amynodon 
sp.

Protoreodon 
petersoni 
Wilson 
1971a 


Protoreodon 
pumilus 
Wilson 
1971a 


Leptoreodonmarshi 
Wilson 
1974 


Toromeryx 
marginatus 
Wilson 
1974 


*ln 
addition 
a 
large 
amynodont 
lower 
jaw 
was 
loaned 
for 


studybut 
has,
sincebeen 
lost.Itwastentativelyidentifiedby 


me 
as 
Megaiamydon 
and 
was 
last 
seen 
at 
the 
American 
Mu


seum 
of 
Natural 
History, 
New 
York. 
Any 
assistance 
in 
its 


relocation 
will 
be 
greatly 
appreciated. 


Table 
2. 
Distribution 
of 
Candelaria 
l.f. 
in 
Colmena 
Tuff 


Lower 
sorted 
facies 
Middle 
lahar 
facies 
(lower 
50 
ft.) 
(15m) 
Amynodonsp. 


Helix 
leidyi

Oreohelix 
grangeri 
Upper 
Glass 
facies 
Alligator 
or 
crocodile 
(upper 
25 
ft.) 
PPeratherium 
Onomyid 
gen. 
etsp. 
indet 
Manitsha 
sp. 


Manitsha 
johanniculi 
Leptotomus 
leptodusIschryotomus 
cf. 
/. 
petersoni 
Prolapsus 
sp. 
Leptotomus 
leptodus 
Protoreodon 
petersoniProlapsus 
sp. 
Protoreodon 
pumilus

Harpagolestes 
sp. 


Harpagolestes 
sp. 


Epihippus 
cf. 
E. 
gracilis 


Sthenodectes 
australis 


Dilophodon 
n. 
sp.

Colodon 
cf. 
C. 
hancocki 


amnyodont, 
not 
identified 


Protoreodon 
petersoni

Protoreodon 
pumilus

Leptoreodon 
marshi 


Toromeryx 
marginatus 


13 



tion 
of 
E. 
gracilis. 
Protoreodon 
petersoni, 
a 
small 
protoreodont, 
is 
found 
in 
the 
Candelaria 


l.f. 
but 
not 
in 
the 
overlying 
Porvenir 
I.f. 
The 
very 
small 
P. 
minimus, 
however, 
occurs 
at 
McCarty's 
Mountain 
in 
the 
Chadronian 
of 
Montana, 
so 
it 
is 
possible 
that 
a 
comparablysmall 
form 
will 
be 
found 
in 
the 
Porvenir 
l.f. 
The 
type 
of 
P. 
petersoni 
is 
from 
the 
Uinta 
C, 
Myton 
Pocket, 
Uinta 
County, 
Utah. 
In 
Texas, 
Protoreodon 
pumilus, 
a 
larger 
protoreodont,
extends 
from 
the 
Candelaria 
l.f. 
to 
the 
Chadronian 
Porvenir 
l.f. 
in 
the 
lower 
part 
of 
the 
Chambers 
Tuff. 
The 
latter 
occurrence 
is 
the 
highest, 
to 
my 
knowledge, 
and 
the 
only 
one 
where 
Protoreodon 
pumi/us 
is 
associated 
with 
a 
Chadronian 
fauna. 
In 
Utah, 
P. 
pumilus 
is 
found 
as 
low 
as 
Uinta 
B. 
Emry 
(1975) 
reviewed 
the 
occurrences 
of 
Protoreodon 
at 
Beaver 
Divide 
and 
assigns 
them 
to 
the 
Uintan. 
Toromeryx 
is 
endemic 
and 
therefore 
of 
no 
assistance 
for 
correlation. 
According 
to 
Wood 
(1974, 
p. 
104): 
"Four 
of 
the 
six 
rodent 
specimens 
from 
the 
Colmena 
Tuff 
(Candelaria 
local 
fauna) 
are 
referred 
to 
species 
previously 
known 
from 
the 
late 
Eocene 
Uinta 
Formation 
of 
Utah 
(Leptotomus 
leptodus 
and 
Ischyrotomuspetersoni, 
each 
occurring 
in 
both 
the 
Wagon-
hound 
and 
Myton 
local 
faunas). 
The 
other 


two 
specimens 
are 
useless 
in 
correlation. 


Leptotomus 
leptodus 
is 
more 
advanced 
than 


the 
material 
of 
the 
same 
species 
from 
the 


Myton. 
The 
rodent 
evidence, 
then, 
suggests

that 
the 
Colmena 
(Candelaria 
1.f.) 
ispost-My


ton 
in 
age 
but 
probably 
not 
very 
much 
later." 


Buckshot 
Ignimbrite 


The 
Buckshot 
Ignimbrite 
(figs. 
5,7, 
8) 
is 
a 
very 
important 
marker 
throughout 
the 
Vieja 
area. 
It 
is 
easily 
identifiable 
from 
hand 
specimens, 
and 
its 
upper 
surface 
in 
many 
areas 
is 
covered 
with 
hemispherical 
mounds 
properly 
called 
tumuli 
but 
informally 
known 
as 
"blister 
cones." 
These 
make 
the 
Buckshot 
easy 
to 
identify 
at 
a 
distance. 
The 
ignimbrite 
is 
more 
resistant 
to 
erosion 
than 
the 
Colmena 
below 
or 


the 
Chambers 
above 
and 
therefore 
caps 
mesas 


and 
buttes, 
and 
forms 
prominent 
dip 
slopes. 


Anderson 
(1975), 
in 
a 
recently 
completedstudy 
of 
the 
Buckshot, 
states 
(p. 
13): 


"The 
Buckshot 
Ignimbrite 
is 
a 
zoned 
ash-
flow 
sheet 
composed 
of 
one 
simple 
coolingunit 
and 
overlain 
by 
an 
air-fall 
ash 
depositthat 
is 
believed 
to 
be 
a 
product 
of 
the 
same 
explosive 
eruption. 
The 
Buckshot 
is 
exposedin 
a 
narrow 
belt 
extending 
75 
km. 
from 
north 
to 
south 
and 
15 
km. 
from 
east 
to 
west 


. 


. 


Its 
color 
varies 
from 
grayish 
brown 
to 
.
dark. 
reddish 
brown, 
the 
reddish 
brown 
most 
often 
found 
on 
weathered 
surfaces 
In 
outcrop

. 
... 


or 
hand 
specimen, 
easily 
recognizable 
constituents 
are 
colorless 
phenocrysts 
of 
alkali 
feldspar, 
glass 
shards, 
fragments 
of 
intermeditate 
volcanic 
rocks 
and 
various 
secondaryminerals 
filling 
cavities 
in 
the 
rock." 


The 
Buckshot 
provides 
a 
time 
plane 
because 
as 
a 
single 
cooling 
unit 
it 
must 
have 
been 
deposited 
very 
rapidly. 
For 
this 
reason 
a 
postassium-argon 
date 
was 
felt 
to 
be 
very 
important.


Three 
dates 
are 
listed 
by 
Wilson 
et 
al. 
(1968) 
for 
the 
Buckshot 
Ignimbrite 
: 


±±

34.7 
2.0, 
35.2 
2.3 
and 
38.6 
± 
1.2. 
Of 
these, 
the 
38.6 
was 
chosen 
as 
the 
best 
date 
because 
it 
is 
older 
than 
the 
36 
m.y. 
dates 
on 
the 
Bracks 
Rhyolite 
which 
is 
stratigraphicallyhigher. 
This 
choice 
has 
been 
substantiated 
bythe 
whole 
suite 
of 
dates 
on 
flow 
rocks 
in 
the 
northeastern 
Davis 
Mountains, 
which 
are 
36 
37.5 
m.y. 
(fig. 
3, 
sec. 
7, 
table 
15) 
and
-

which, 
like 
the 
Bracks 
Rhyolite, 
overlie 
Oligocene 
vertebrates 
(Sellards 
et 
al. 
1933, 


p. 
805). 
The 
date 
of 
38 
m.y. 
for 
the 
beginning 
of 
the 
Chadronian 
(Berggren 
and 
van 
Couvering 
1974) 
now 
seems 
well 
established. 
In 
the 
north-central 
and 
western 
parts 
of 
the 
Vieja 
area 
the 
Buckshot 
pinches 
out 
and 
the 
Chambers 
Tuff 
concordantly 
overlies 
the 
Colmena. 
The 
two 
are 
sufficiently 
distinct 


lithologically 
to 
be 
easily 
distinguished 
without 
the 
Buckshot. 


Chambers 
Tuff 


The 
Chambers 
Tuff 
was 
defined 
by 
DeFord 


14 



feet300

lower


the 


of

interval


stratigraphic


The

FMNH.


the 


at

labels


top 
to

Ignimbrite
Buckshot


from 


section


7.—Diagrammatic


Fig.

Die-

Arroyo


to

northMesa 
Carr 
from

extending
Chambers


the 


of 


those 


areunits

informal


4.The


figure

in

given

Location


Cliff.

Bigof

a 
is


40492


TMM


l.f.
Porvenir


5.
the 
table

of 


most 
mount,"

of 
“red

source 


as 
the 


is 


known


chiocholocality
specimen


onusedareand

notes


field

his 


in

Patterson


Bryan

by

given


Chambers 


the 


of 


part

lower


the 


of

section


B.—Diagrammatic


Fig.

position
showing


area


Vieja

southern


the 


in

Springs
Adobe


near


Tuff

l.f.
Porvenir


the 


of

elements


containing


unit

fossiliferous


of 



(1958) 
as 
"the 
strata 
between 
the 
top 
of 
the 
Buckshot 
Ignimbrite 
and 
the 
base 
of 
the 
Bracks 
Rhyolite." 
The 
term 
tuff 
is 
misleading 
because 
most 
of 
the 
Chambers 
consists 
of 
water-laid 
sediments. 
Individual 
beds 
rangefrom 
coarse 
conglomerate 
lenses 
containingbone 
fragments, 
to 
units 
of 
sand, 
silt, 
or 
clay.
The 
conglomerates 
contain 
cobbles 
of 
fossiliferous 
Cretaceous 
limestone 
and 
fragmentsof 
igneous 
rock. 
The 
conglomerates 
are 
usually 
gray 
but 
the 
finer 
grained 
units 
are 
more 
colorful 
and 
can 
be 
brick 
red, 
salmon 
red,
pink, 
greenish 
brown 
or 
dark 
brown. 
The 
lower 
part 
of 
the 
formation 
is 
well 
exposed 
at 
Big 
Cliff 
and 
the 
surrounding 
area 
(figs.
4,7). 
Walton 
(1972, 
1975) 
has 
studied 
the 
sediments 
of 
the 
Vieja 
Group 
in 
detail 
and 
has 
made 
the 
very 
valuable 
contribution 
of 
recognizing 
and 
tracing 
lower 
and 
upper 
marker 
beds 
within 
the 
Chambers 
(figs. 
7,8). 
Although 
he 
does 
not 
map 
the 
marker 
beds, 
he 


very 
carefully 
describes 
their 
color, 
lithology,
stratigraphic 
position, 
and 
distribution: 


"The 
lower 
of 
these 
marker 
beds 
is 
a 
tuff 
bed, 
6 
to 
30 
feet 
thick 
that 
crops 
out 
1GO-
175 
feet 
above 
the 
Buckshot... 
it 
is 
the 
same 
bed 
described 
as 
'white 
volcanic 
dust' 
at 
the 
Big 
Cliff 
mammal 
locality 
by 
Stovall 
(1948, 
see 
also 
Mankin, 
1955). 
The 
bed 
is 
white 
to 
pale 
orange 
or 
pale 
green 
and 
usually 
is 
less 
resistant 
to 
weathering 
than 
beds 
above 
and 
below 
it. 
." 
(Walton 
1972, 
p. 
79).

. 


The 
upper 
marker 
bed 
of 
Walton 
(1972, 
1975) 
had 
been 
previously 
recognized 
by 
students 
mapping 
in 
the 
area. 
It 
was 
informally 
named 
the 
Chambers 
red 
siltstone 
lentil 
by 
Peterson 
(1955) 
but 
the 
name 
was 
changed 
when 
DeFord 
formally 
described 
the 
Chambers 
Tuff. 
Twiss 
(ms. 
map 
of 
Vieja 
area) 
maps 
this 
unit 
as 
the 
"Rooney 
siltstone 
lentil." 
It 
is 
a 
hard, 
resistant, 
brick 
red 
unit 
that 
forms 
dip 
slopes 
and 
caps 
buttes 
and 
mesas 
where 
the 
Bracks 
has 
been 
removed. 
Walton 
(1972, 


p. 
83) 
describes 
it 
as 
follows: 
"Eighty 
percent 
of 
it 
is 
silt-to-fine 
sand-
sized, 
well 
sorted, 
euhedral, 
overgrown 
sanidine. 
Grains 
of 
volcanic 
quartz, 
slightly 
coars


er 
than 
the 
sanidine, 
total 
about 
5% 
of 
the 
rock. 
It 
is 
cemented 
by 
fine-grained 
quartzand 
calcite 
that 
amount 
to 
about 
15 
to 
20 
percent 
of 
the 
rock. 
Evidence 
that 
the 
upper 
marker 
bed 
itself 
is 
a 
tuff 
is 
that 
it 
uniformly 
covers 
such 
a 
large 
area; 
is 
of 
quitedifferent 
composition 
than 
any 
other 
unit 
of 
the 
Chambers 
section; 
and, 
though 
well 
sorted 
is 
marked 
by 
no 
sedimentary 
structures, 
unlike 
most 
well 
sorted 
sedimentary 
rocks." 


The 
"upper 
marker 
bed" 
of 
Walton 
(1972,1975) 
or 
the 
"Rooney 
siltstone 
lentil" 
of 
Twiss 
(ms. 
map) 
holds 
up 
Dunagan 
Mesa 
and 
Carr 
Mesa 
that 
lie 
to 
the 
east 
and 
south 
of 
Big 
Cliff. 


Mankin's 
thesis 
(1955) 
contains 
stratigraph


ic 
sections 
and 
correlations 
of 
the 
lower 
part 
of 
the 
Chambers 
from 
the 
field 
notes 
of 
Bryan 
Patterson 
that 
were 
made 
in 
1946. 
Patterson 
refers 
to 
what 
is 
now 
the 
Buckshot 
as 
the 
"basal 
Vieja 
lava" 
and 
Walton's 
lower 


marker 
bed 
as 
"Yellow 
white 
tuff, 
the 
white 
layer." 
Patterson 
uses 
the 
"white 
layer."
(fig. 
7) 
to 
correlate 
from 
Big 
Cliff 
north 
to 
Soldier 
Camp 
Flat. 
The 
stratigraphic 
interval 
between 
the 
Buckshot 
and 
the 
lower 
marker 
bed 
is 
Patterson's 
"Big 
Red 
Horizon" 
and 
an 
interval 
up 
to 
approximately 
100 
feet 
above 
the 
lower 
marker 
bed 
he 
calls 
the 
"Blue 
Cliff 
Horizon." 


Walton 
(1972, 
p. 
79) 
believes 
the 
lower 
marker 
bed 
is 
an 
ash 
flow 
tuff 
which 
he 
recognizes 
from 
the 
southern 
to 
the 
northern 
extremes 
of 
the 
Vieja 
area, 
a 
distance 
of 
about 
40 
miles. 
The 
lower 
marker 
bed 
is 
especiallyuseful 
in 
the 
Big 
Cliff-Soldier 
Camp 
Flat 
area 
because 
most 
of 
the 
Porvenir 
l.f. 
came 
from 
either 
the 
hundred 
feet 
of 
strata 
just 
below 
or 
above 
it. 
The 
lower 
marker 
bed 
has 
not 
been 
submitted 
for 
potassium-argon 
dating, 
but 
it 
would 
be 
a 
most 
useful 
one 
and, 
if 
the 
sample 
were 
suitable, 
would 
form 
an 
excellent 
time 
plane 
just 
above 
the 
Buckshot. 
However, 
it 
might 
well 
be 
that 
the 
dating 
method 
would 


not 
be 
able 
to 
resolve 
the 
time 
difference 
between 
it 
and 
the 
Buckshot. 
The 
time 
span 
must 
have 
been 
short 
because 
I 
am 
unable 
to 
detect 
evolutionary 
changes 
within 
the 
Porvenir 
l.f. 
which 
extends 
from 
just 
above 
the 


17 



Buckshot 
to 
about 
100 
feet 
above 
the 
lower 
marker 
bed. 


Figure 
7 
is 
a 
measured 
section 
of 
the 
lower 
part 
of 
the 
Chambers 
Tuff 
from 
the 
Buckshot 
Ignimbrite 
to 
the 
top 
of 
Big 
Cliff 
(fig. 
4, 
sec. 
B) 
and 
includes 
the 
lower 
marker 
bed. 
The 
greatest 
variety 
of 
taxa 
of 
the 
Porvenir 
l.f. 
were 
found 
in 
the 
lower 
part 
of 
the 
Chambers 
Tuff. 
All 
but 
one 
of 
the 
TMM 
localities 
from 
this 
part 
of 
the 
section 
were 
isolated 
surface 
finds. 
The 
single 
exception 
is 
TMM 
40492,
"red 
mound," 
where 
a 
concentration 
of 
material 
listed 
in 
table 
5 
was 
found. 
Figure 
8 
is 
a 
measured 
section 
of 
the 
lower 
part 
of 
the 
Chambers 
Tuff 
from 
the 
Buckshot 
to 
the 
lower 
marker 
bed 
near 
Adobe 
Spring 
south 
of 
Capote 
Creek 
with 
the 
stratigraphic 
positionof 
additional 
elements 
of 
the 
Porvenir 
l.f. 
Adobe 
Spring 
(fig. 
4, 
sec. 
C) 
is 
labeled 
"Mexican 
Spring" 
on 
the 
map 
in 
Mankin 
(1955).

The 
upper 
boundary 
of 
the 
Chambers 
Tuff 
is 
placed 
at 
the 
base 
of 
the 
Bracks 
Rhyolite(DeFord 
1958).. 
The 
Bracks, 
unfortunately, 
is 
not 
present 
in 
the 
area 
north 
of 
Soldier 
Flat. 
Here, 
uppermost 
Chambers 
and 
the 
lower 
Capote 
Mountain 
are 
so 
similar 
lithologicallythat 
in 
places 
it 
is 
difficult 
to 
distinguishthem. 
A 
third 
or 
uppermost 
marker 
bed, 
however, 
was 
used 
by 
Schulenberg 
(1958). 
He 
described 
it 
as 
follows: 
"The 
Chambers-CapoteMountain 
contact 
or 
the 
horizon 
of 
the 
Bracks, 
has 
been 
approximated 
in 
the 
Porvenir 
area 
by 
mapping 
the 
upper 
contact 
of 
a 
moderate 
red 
sandstone 
which 
immediatelyunderlies 
the 
Bracks 
where 
the 
Bracks 
is 
present" 
(Schulenberg 
1958, 
p. 
49).

Two 
important 
localities, 
Reeves 
bone-
bed 
and 
Chalk 
Gap 
Draw, 
occur 
in 
the 
area 
where 
the 
Bracks 
is 
absent. 
The 
red 
sandstone 
is 
present 
in 
the 
Reeves 
bonebed 
area 
and 
is 
the 
uppermost 
sandstone 
in 
figure 
9. 
A 
measured 
section 
was 
not 
made 
in 
the 
Chalk 
GapDraw 
area 
but 
the 
specimens 
from 
there 
and 
Reeves 
bonebed 
form 
the 
Little 
Egypt 
l.f. 
and 


are 
at 
approximately 
the 
same 
level. 


Porvenir 
Local 
FaunaTable 
3 
includes 
all 
taxa 
of 
the 
Porvenir 
l.f. 
with 
the 
originaland 
some 
important 
references 
to 
those 
taxa. 
Tables 
4-7 
list 
parts 
of 
the 
Pon/enir 
l.f. 
from 


specific 
stratigraphic 
levels 
or 
geographic 
areas. 
Table 
4 
lists 
only 
those 
taxa 
of 
the 
Porvenir 
l.f. 
that 
were 
found 
in 
the 
lower 
100 
feet 
of 
the 
Chambers 
Tuff 
or 
beneath 
the 
lower 
marker 
bed. 
This 
unit 
is 
called 
the 
"BigRed 
horizon" 
in 
the 
field 
notes 
of 
Bryan 
Pat


terson 
at 
the 
Field 
Museum 
of 
Natural 
History, 
Chicago. 
It 
is 
also 
the 
"main 
fossil 
level" 
of 
Stovall 
(1948). 
Taxa 
from 
the 
TMM 
localities 
"at 
the 
foot 
of 
Big 
Cliff," 
"north 
of 
Big 
Cliff," 
and 
40263 
for 
the 
skull 
of 
Hemipsalodon 
are 
also 
included 
in 
table 
4. 


Table 
5 
lists 
those 
taxa 
of 
the 
Porvenir 
l.f. 
that 
were 
found 
at 
the 
locality 
known 
as 
"red 
mound 
north 
of 
Big 
Cliff." 
The 
rocks 
at 
this 
locality 
are 
less 
than 
five 
feet 
below 
the 
lower 
marker 
bed. 
Table 
6 
lists 
taxa 
included 
in 
the 
Porvenir 
l.f. 
that 
were 
found 
between 
0 
and 
88 
feet 
above 
the 
lower 
marker 
bed. 
This 
unit 
is 
the 
"Blue 
Cliff 
horizon" 
in 
the 
field 
notes 
of 
Bryan 
Patterson 
at 
the 
FMNH. 
Table 
7 
lists 
only 
those 
taxa 
of 
the 
Porvenir 
l.f. 
that 
were 
found 
near 
Adobe 
Springs 
in 
the 
southern 
part 
of 
the 
Vieja 
area. 


Little 
Egypt 
Local 
Fauna 
Table 
8 
lists 
all 
the 
taxa 
and 
original 
references 
to 
the 
Little 
Egypt 
l.f. 
Table 
9 
is 
restricted 
to 
taxa 
from 
Reeves 
Bonebed, 
and 
Table 
10 
to 
taxa 


from 
Chalk 
Gap 
Draw. 


Capote 
Mountain 
Tuff 


In 
the 
northern 
part 
of 
the 
Vieja 
area 
the 
Capote 
Mountain 
is 
a 
fine-grained, 
vitric, 
tuffaceous 
sandstone 
and 
siltstone. 
Unfortunate


ly, 
there 
are 
no 
marker 
beds 
in 
the 
CapoteMountain 
along 
Walker 
Creek. 
The 
bulk 
of 
the 
Capote 
Mountain 
in 
this 
area 
is 
a 
succession 
of 
pinkish 
gray 
to 
dark 
brown 
spheroidally 
weathered, 
fining 
upward 
siltstone 
and 
sandstones. 
Very 
faint 
cross-bedding 
is 
found 
in 
some 
siltstones 
but 
distinct 
sedimentary 
structures 
are 
rare. 
Clay 
pebbles 
form 
lenses 
of 
conglomerate 
and 
are 
irregularly 
distributed 
in 
the 
sandstone 
and 
siltstone. 


The 
stratigraphic 
position 
of 
the 
Airstrip

l.f. 
is 
estimated 
as 
570 
feet 
above 
the 
Bracks 
Rhyolite. 
Although 
most 
of 
the 
specimensfrom 
the 
Airstrip 
l.f. 
were 
found 
within 
a 
18 



Chambers 


the 


of 


part

upper


of

section


9.-Diagrammatic


Fig.

marker


sandstone
salmon-red


the 


Bonebedto 
Reeves 


from 
Tuff 


Rhyolite.
Bracks


the 


of

basethe

marks


thatbed


Table 
3. 
Porvenir 
local 
fauna, 
early 
Chadronian 
[Table 
3, 
continued] 


Taxon 


Planorbis 
sp.
Mesodon 
("Helix") 
leidyi 


Lacertilia 
(not 
seen) 
Herpetologicalmaterial, 
unstudied 
Rooneyia 
viejaensis 


Geolabis 
n. 
sp. 


Leptictis 
douglassi

Apternoduscf. 
A. 
brevirostris 


L 
ep 
totomus 
gigans

Microparamys 
perfossus

Ischryotomus 
cf. 
/. 
petersoni

Manitsha 
joahniculi

Ischryomys 
blacki 


Pseudocylindrodon 
neglectus

Pseudocylindrodon 
texanus 


Ardynomys 
occidentalis 


Adjidaumo 
cf. 
A. 
minutus 


Viejadjidaumo 
magniscopulicf. 
Viejadjidaumo, 
sp. 
indet. 
Aulolithom 
ysbouni 
tes 
Yoderimyslustrorum 
Eutypomys 
inexpectatuscf. 
Eutypomyid, 
gen. 
et 
sp. 
indet. 
cf. 
Simimys, 
sp. 
indet. 
IschnognathussavageiHemipsalodon 
n. 
sp.
Hyaenodon 
sp. 
Miacis 
n. 
sp.
Daphoenussp.
Haplohippus 
texanus 
(Mesohippus 
cf. 
M. 
bairdi) 


Mesohippustexanus 


Mesohippussp. 


Menodus 
baked 


Teleodus 
sp. 


Colodon 
n. 
sp. 


Caenopus 
sp.

Hyracodon 
sp. 


Metamynodon 
sp. 


Schizotheroides 
jackwilsoni

Brachyhyops 
wyominensis 


Reference 


Stovall 
1948 
Goldich 
& 
Elms 
1949, 


L. 
S. 
Russell;
Pampe 
1974;
Stovall 
1948 
Wilson 
1966;
Hoffer 
& 
Wilson 
1967;
Szalay 
1976; 
Jerison 
1973; 
Szalay 
& 
Wilson 
1976 
Lillegraven, 
pers. 
com. 
1972 
Novacek 
1976 
Novacek 
1976 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Wood 
1974 


Stovall 
1948 


Gustafson, 
in 
progressGustafson, 
in 
progressGustafson, 
in 
progressGustafson, 
in 
progressMcGrew 
1953 
Stovall 
1948; 
but 
see 
McGrew 
1971; 
Forsten 


1971a, 
b; 
Clark 
et 
al. 
1967 


McGrew 
1971; 
Forsten 
1971a,b 
McGrew 
1971; 
Forsten 
1971a, 
b 


Stovall 
1948; 
Wilson 
1977 


fide 
Clark 
et 
al. 
1967;
Wilson 
1977 
Stovall 
1948=Co/oc/or7 


n. 
sp., 
Schiebout, 
in 
progressSchiebout, 
in 
progressStovall 
1948; 
Schiebout, 
in 
progressSchiebout, 
in 
progress
Schiebout 
1977 
Wilson 
1971b 


Taxon 


Archaeotherium 
cf. 
A 
mortoni 
Protoreodon 
pumilusAgriochoerusantiquus 


Aclistomycter 
middletoni 
Mercoidodontidae 
gen. 
et 
sp. 
indet. 
Heteromeryx 
disparPoabromyluskayiPoabromylus 
minor 
Oromeryx 
sp. 
Eotylopus 
cf. 
E. 
reedi 
Hidrosotherium 
transpecosensisLeptomeryx 
defordi 


Reference 


Wilson 
1971b 
Wilson 
1971a 
identified 
as 
Merycoidodon 
cuibertsoni, 


M. 
gracilis, 
and 
Mesohippus 
texanus 
in 
Stovall 
1948. 
Wilson 
1971a 
Wilson 
1971a 
Wilson 
1974 
Wilson 
1974 
Wilson 
1974 
Wilson 
1974 
Wilson 
1974 
Wilson 
1974 
Wilson 
1974 
Table 
4. 
Taxa 
found 
in 
the 
lower 
100 
feet 
of 
Chambers 
Tuff 
or 
beneath 
the 
lower 
marker 
bed; 
Porvenir 
l.f. 


Herpetological 
material, 
unstudied 


Leptotomusgigans 


Ischyrotomus 
cf. 
petersoni 


Eutypomys 
inexpectatus

Pseudocylindrodon 
neglectus

Manitshajohanniculi

Hyaenodon 
sp. 


Hemipsalodon 
n. 
sp. 


Ischnognathussavagei 


Haplohippus 
texanus 


Mesohippus 
texanus 


Mesohippussp. 


Menodus 
bakeri 


Teleodus 
sp. 


Colodon 
n. 
sp.

Hyracodon 
sp.

Metamynodonsp. 


Coenopus 
sp.

Schizotheroides 
jackwilsoni 


Brachyhyops 
wyomingensis 


Protoreodon 
pumilus

Agriochoerus 
antiquus 


Heteromeryx 
dispar 


Poabromylus 
minor 


Poabromylus 
kayi 


Leptomeryx 
defordi 


20 



Table 
5. 
The 
following 
taxa 
included 
in 
the 
Porvenir 
l.f. 
Table 
7. 
The 
following 
taxa 
included 
in 
the 
Porvenir 
l.f. 
were 
found 
just 
below 
(less 
than 
5 
feet) 
"the 
lower 
marker 
were 
found 
at 
localities 
in 
the 
southern 
part 
of 
the 
Vieja 
bed" 
of 
Walton 
(1972) 
in 
the 
Chambers 
Tuff 
at 
locality 
area 
near 
Adobe 
Springs, 
25-42 
ft. 
above 
the 
Buckshot 
"red 
mound, 
north 
of 
Big 
Cliff," 
TMM 
40492 
Ignimbrite. 


Gastropods, 
unstudied 
Herpetological 
material, 
unstudied 
Geolabis 
n. 
sp.
Apternoduscf. 
brevirostris 
Aulolithomysbounites 
Viejadjidaumo 
magniscopuliMicroparamys 
perfosuscf. 
Viejadjidaumo 
sp. 
indet. 


Adjidaumocf. 
minutus 
Yoderimys 
lustrorum 
cf. 
Leptotomus 
gigans

PseudocylindrodonneglectusMesohippustexanus 
Colodon 
n. 
sp.

Hyracodon 
sp. 
Agriochoerusantiquus 
Leptomeryx 
defordi 


Table 
6. 
The 
following 
taxa 
included 
in 
the 
Porvenir 
l.f. 
were 
found 
between 
0-88 
feet 
above 
the 
"lower 
marker 
bed” 
of 
Walton 
(1972) 
in 
the 
Chambers 
Tuff. 
This 
unit 
is 
the 


"Blue 
Cliff 
horizon" 
in 
the 
field 
notes 
of 
Bryan 
Patterson 
at 
the 
Field 
Museum 
of 
Natural 
History, 
Chicago. 


Gastropods,unstudied 
Herpetological 
material, 
unstudied 
Rooneyia 
viejansisLeptictis 
douglassiHyaenodon 
sp.
Mesohippustexanus 
Teleodus 
sp.
Colodon 
n. 
sp.
Hyracodon 
sp. 
Metamynodon 
sp. 
Caenopus 
sp. 
Protoreodon 
pumilusArchaeotherium 
cf. 
mortoni 
Agriochoerus 
antiquus 
Oromeryx 
sp.
Eotylopus 
cf. 
reedi 
Hidrosotherium 
transpecosensis 
Leptomeryx 
defordi 


five-foot 
interval, 
occasional 
turtle 
carapaces 
and 
isolated 
bones 
were 
found 
lower 
and 
higher 
in 
the 
section. 
The 
bones 
are 
usually 
found 
in 
nodules 
that 
seem 
to 
be 
the 
result 
of 
the 
spheroidal 
weathering. 
Walton 


(1972, 
p. 
85) 
says 
that: 


Gastropods, 
unstudied 
Herpetological 
material, 
unstudied 
Leptotomus 
gigansMicroparamys 
perfossusIschryotomusblacki 
Aclistomyctermiddletoni 


Table 
8. 
Little 
Egypt 
local 
fauna, 
Chadronian 


Reference

Taxon 


Helix 
leidyi 
Pampe 
1974 


Leptictis 
wilsoni 
IMovacek 
1976 
Manitshajoahanniculi 
Wood 
1974 
Cylindrodon 
fontis 
Wood 
1974 
Pseudocylindrodon 
neglectus 
Wood 
1974 
Pseudocylindrodon 
texanus 
Wood 
1974 
Ardynomys 
occidentalis 
Wood 
1974 
Aulolithomys 
cf. 
A. 
bounites 
Wood 
1974 


Eutpomys 
inexpectatus 
Wood 
1974 


Hyaenodon 
sp. 
Gustafson, 
in 
progress

Miacis 
n. 
sp. 
Gustafson, 
in 
progress

Daphaenocyon 
sp. 
Gustafson, 
in 
progress

Fetid 
gen. 
et 
sp. 
indet. 
Gustafson, 
in 
progress

Mesohippustexanus 


Menodusbaked 
Wilson 
1977 


Colodon 
n. 
sp. 
Schiebout, 
in 
progress

Hyracodon 
sp. 
Schiebout, 
in 
progress

Schizotheroidesjackwilsoni 
Schiebout 
1977 


Archaeothenum 
cf. 
A. 
mortoni 


Wilson 
1971b 


Agriochoerusantiquus 
Wilson 
1971a 


Bathygenys 
reevesi 
Wilson 
1971a 


Merycoidodon 
dunagani

Eotylopus 
cf. 
E. 
reedi 
Wilson 
1974 


“Spheroidal 
weathering 
is 
common 
in 
poorly 
bedded 
intervals 
rich 
in 
diagenetic 
clayand 
clinoptilolite 
shard 
pseudomorphs 
in 
which 
the 
clay 
expands 
as 
it 
is 
wetted 
byrainfall 
and 
contracts 
when 
dried." 


Nodules 
that 
contain 
skulls 
often 
had 
the 
main 
line 
of 
fracture 
passing 
longitudinallythrough 
the 
tooth 
row. 
On 
some 
specimens 
a 
concentration 
of 
very 
hard 
hematite 
next 
to 
the 
bone 
or 
dentine 
made 
cleaning 
very 
difficult. 
The 
tuffaceous 
sandstones 
are 
consolidated 
and 
not 
suitable 
for 
washing. 
In 
an 
at


21 



tempt 
to 
increase 
the 
collection 
200 
nodules 
were 
broken 
open 
but 
not 
a 
single 
one 
contained 
bone. 
In 
addition, 
an 
area 
of 
about 
400 
square 
feet 
of 
nodules 
was 
raked 
over. 
The 
idea 
was 
that 
at 
least 
as 
many 
nodules 
should 
occur 
with 
the 
bone 
exposed 
on 
the 
lower 
side. 
Only 
one 
additional 
specimen 
was 
found 
within 
this 
area. 
Table 
11 
lists 
the 
taxa 
in 
the 
Airstrip 
l.f. 


Table 
9. 
The 
following 
taxa 
included 
in 
the 
Little 
Egypt

l.f. 
were 
collected 
from 
or 
very 
close 
to 
"Reeves 
Bonebed,"
in 
the 
upper 
part 
of 
the 
Chambers 
Tuff. 
Gastropods, 
unstudied 


Herpetological 
material, 
unstudied 
Manitsha 
johanniculiLeptictis 
wilsoni 


Cylindrodon 
fontis 
Pseudocylindrodon 
neglectusArdynomys 
occidentalis 
Aulolithomys 
bounites 
Eutypomys 
inexpectatusHyaenodon 
sp. 
Miacis 
n. 
sp.

Daphyaenocyon 
sp.
Felid, 
gen. 
et 
sp. 
indet. 


Mesohippus 
texanus 
Menodusbaked 


Colodon 
n. 
sp.
Hyracodon 
sp. 
AgriochoerusantiquusBathygenysreevesi 


Merycoidodon 
dunaganiEotylopus 
cf. 
E. 
reedi 


Table 
10. 
The 
following 
taxa 
included 
in 
the 
Little 
Egypt 


l.f. 
were 
collected 
from 
localities 
in 
Chalk 
Gap 
Draw 
in 
the 
upper 
part 
of 
the 
Chambers 
Tuff. 
Gastropods, 
unstudied 


Herpetological 
material, 
unstudied 


Pseudocylindrodon 
texanus 


Menodus 
baked 


Schizotheroides 
jackwi!soni 


Archaeothedum 
cf. 
mortoni 


Merycoidodon 
dunagani

Eotylopus 
cf. 
reedi 


Vieja 
Group 
Undifferentiated 


The 
name 
Vieja 
Group 
undifferentiated 
is 
used 
where 
a 
volcanic 
unit 
and 
one 
or 
more 
of 
the 
marker 
beds 
are 
absent 
either 
by 
pinch-
out 
or 
faulting, 
and 
it 
is 
not 
possible 
to 
determine 
the 
boundary 
of 
a 
sedimentary 
unit. 
This 
must 
be 
done 
only 
at 
the 
Ash 
Spring 
locality. 
Although 
the 
rodents 
suggest 
that 
the 
Ash 
Spring 
l.f. 
is 
the 
youngest, 
its 
exact 
stratigraphic 
relationship 
to 
the 
beds 
that 
contain 
the 
other 
local 
faunas 
cannot 
be 
determined 
because 
of 
faulting.

The 
Ash 
Spring 
locality 
was 
studied 
and 
collected 
in 
1966 
and 
1967 
by 
John 
M. 
Harris. 
It 
was 
discovered 
and 
mapped 
by 
Bridgesand 
Dasch 
and 
first 
described 
by 
Bridges(1958). 
Bridges 
placed 
the 
sediments 
at 
the 
Ash 
Spring 
locality 
in 
the 
upper 
part 
of 
the 
Capote 
Mountain 
but 
this 
assignment 
cannot 
be 
proven 
because 
of 
the 
absence 
of 
the 
marker 
beds 
or 
marker 
flows 
in 
the 
area. 


The 
Ash 
Spring 
locality 
is 
the 
northernmost 
and 
westernmost 
one 
in 
the 
Vieja 
area. 
The 
sediments 
are 
poorly 
consolidated 
and 
their 
color, 
a 
light 
pinkish 
gray, 
resembles 
the 
Miocene 
and 
younger 
bolson 
fill. 
The 
location 
(N3o°37'W 
104°53'30") 
is 
shown 
on 
figures 
1 
and 
4H, 
and 
on 
Bennett 
Ranch 
Quadrangle, 
Texas, 
USGS 
7.5' 
series 
(topographic). 
Bridges 
(1958) 
and 
Harris 
(1967a)
give 
measured 
sections 
of 
the 
Ash 
Spring 
area. 


Table 
11. 
The 
following 
taxa 
were 
found 
at 
or 
very 
close 
to 
TMM 
40504 
approximately 
570 
ft. 
above 
the 
Bracks 
Rhyolite 
in 
the 
CapoteMt. 
Tuff, 
Airstrip 
1.f., 
Chadronian. 


Taxa 
References 
Herpetological 
material, 
unstudied 
Subsumus 
candelariae 
Wood 
1974 
Pseudocylindrodon 
cf. 
neglectusJaywilsonomys 
aff. 
pintoensisArdynomys 
occidentalis 
Hyaenodon 
sp.
Hesperocyon 
sp.
Hyracodon 
sp.
Bathygenysreevesi 
Limnenetes 
cf. 
platyceps?Prodesmatochoerus 
cf. 
meekae 
Wood 
1974 
Wood 
1974 
Wood 
1974 
Gustafson, 
in 
progress 
Gustafson, 
in 
progress 
Schiebout, 
in 
progress 
Wilson 
1971a 
Wilson 
1971a 
Wilson 
1971a 
Poebrotherium 
franki 
Wilson 
1974 
Poebrotherium 
sp.
Hypisodus 
cf. 
minimus 
Wilson 
1974 
Wilson 
1974 


22 



Ash 
Spring 
Local 
Fauna 
—Harris 
(1967b)
lists 
the 
taxa 
that 
were 
known 
from 
Ash 
Spring 
as 
of 
that 
date. 
A 
revised 
list 
is 
givenin 
table 
12. 


Garren 
Group 


The 
upper 
member 
of 
the 
Hogeye 
Tuff 
of 
the 
Garren 
Group 
has 
produced 
a 
small 
collection 
of 
vertebrate 
fossils. 
The 
locality 
was 
found 
by 
Underwood 
and, 
although 
it 
is 
not 
labeled 
on 
his 
geologic 
quadrangle 
map 
(Underwood 
1963) 
it 
is 
in 
the 
upper 
member 
of 


the 
Hogeye 
Tuff 
(Underwood 
1963, 
p. 
18) 
and 
is 
located 
near 
his 
measured 
section 
4. 
The 
Garren 
Group 
interfingers 
on 
the 
north 
with 
the 
Vieja 
Group 
and 
the 
Hogeye 
Tuff 
is 
in 
part 
equivalent 
to 
the 
Chambers 
Tuff 
(fig. 
3). 
At 
the 
time 
Underwood 
published 
his 
map 
and 
text 
I 
stated 
that 
the 
faunule 
from 
the 
Hogeye 
correlated 
with 
the 
Ash 
Spring

l.f. 
I 
now 
believe 
it 
much 
more 
probablethat 
the 
faunule 
from 
the 
Hogeye 
Tuff 
correlates 
with 
the 
Porvenir 
l.f. 
Taxa 
identified 
from 
the 
Hogeye 
Tuff 
are 
as 
follows; 
Titanothere 
gen. 
et 
sp. 
indet., 
Mesohippus 
texanus 
(in 
McGrew 
1971), 
Agriochoerus 
antiquus, 
and 
Leptomeryx 
sp. 
Table 
12. 
Ash 
Spring 
local 
fauna, 
Chadronian 


Taxon 
Reference 


Gastropids,unstudied 
Herpetological 
material, 
unstudied 
Avian 
material, 
unstudied 
Titanotheriomys 
veterior 
Harris 
1967a, 
b; 


Wood 
1974 
Pseudocylindrodon 
cf. 
P. 
texanus 
Wood 
1974 
Meliakrouniomys 
wilsoni 
Harris 
& 
Wood 


1969; 
Wood 
1974 
Felid, 
gen. 
et 
sp. 
indet. 
Harris 
1967a 
Rhinoceratid, 
gen. 
et 
sp. 
indet. 
Harris 
1967a 
Toxotherium 
cf. 
T. 
woodi 
Harris 
1967a 
Archaeotherium 
cf. 
A. 
mortoni 
Wilson 
1971b 
Merycoidodontid, 
gen. 
et 
sp. 
indet. 
Harris 
1971a; 


Wilson 
1971a 
Poebrotherium 
franki 
Wilson 
1974 


Oromerycinae,gen. 
et 
sp. 
indet. 
Wilson 
1974 


Hypisodus 
cf. 
H. 
minimus 
Wilson 
1974 


Prietos 
Formation 


A 
small 
area 
of 
volcanic 
flows 
and 
intercalated 
sediments 
occurs 
35 
miles 
northwest 
of 
Ojinaga, 
Chihuahua, 
Mexico. 
The 
area 
was 
mapped 
by 
Grant 
H. 
Heiken 
and 
Ismael 
Ferrusquia-
V.in 
1965. 
Ferrusquia-V.(1969) 
described 
the 
Rancho 
Gaitan 
l.f. 
and 
published 
a 
geologic 
map 
and 
section 
of 
the 
area. 
Heiken 
(1971) 
described 
the 
petrology, 
defined 
the 
Prietos 
Formation, 
and 
tentatively 
identified 
the 
Brite 
or 
Mitchell 
Mesa 
Ignimbrite.
Although 
the 
Rancho 
Gaitan 
area 
is 
not 
partof 
the 
Vieja 
area 
proper, 
the 
local 
fauna 
and 
the 
stratigraphic 
section 
are 
more 
closely 
related 
to 
the 
Vieja 
than 
to 
the 
folded 
marine 
Cretaceous 
that 
bounds 
the 
area 
to 
the 
north, 
west, 
and 
south. 


Rancho 
Gaitan 
Local 
Fauna 
—This 
local 


fauna 
is 
a 
very 
important 
one 
in 
that 
it 
contains 
some 
taxa 
that 
have 
not 
been 
discovered 
the 
Oligocene 
on 
the 
east 
side 
of 
the 
Rio 
Grande, 
for 
example, 
Jaywilsonomys, 
Protoreodon 
petersoni, 
Agriochoerus 
maximus, 
and 
Hypertragulus 
heikeni. 
It 
furnishes 
additional 
valuable 
information 
for 
correlation 
of 
the 
southern 
Chadronian 
faunas 
to 
those 
of 
both 
Montana 
and 
Wyoming 
and 
also 
to 
those 
of 
Southern 
California. 
Table 
13 
lists 
the 
taxa 
assigned 
to 
the 
Rancho 
Gaitan 
l.f. 


Chronostratigraphy, 
Vieja 
Group 


Radiochronology 


One 
of 
the 
long-term 
purposes 
of 
the 
project 
in 
west 
Texas 
is 
to 
tie 
the 
stratigraphic 
position 
of 
vertebrate 
fossil 
faunas 
to 
potassium-argon 
dated 
rocks. 
Samples 
were 
collected 
and 
submitted 
to 
various 
laboratories 
when 
funds 
were 
available. 
The 
first 
results 
were 
incorporated 
in 
Evernden 
et 
al. 
(1964). 
Additional 
dates 
were 
published 
in 
Wilson 
et 
al. 
(1968) 
for 
the 
Vieja 
area; 
and 
in 
Maxwell 
et 
al. 
(1967) 
and 
Maxwell 
and 
Dietrich 
(1970, 
1972) 
for 
Big 
Bend 
National 
Park. 
Potassium-argon 
dates 
for 
the 
Buck 
Hill 
Group 
are 
found 
in 
Gilleland 
et 
al. 
(1969) 
and 
in 
Maxwell 
and 
Dietrich 
(1972). 


23 



Table 
13. 
Rancho 
Gaitan 
local 
fauna, 
Early 
Chadronian 


Taxon 
Reference 
Gastropods, 
unstudied 
Herpetological 
material, 
unstudied 
Mytonomys 
gaitania 
Ferrusquia-V. 
& 
Wood 
1969 
Jaywilsonomysojinagaensis 
Ferrusquia-V 
& 
Wood 
1969 
Jaywilson 
omys 
pintoensis 
Ferrusquia-V 
& 
Wood 
1969 
?Brontops 
cf. 
B. 
brachycephalusPHyracodon 
sp.
Rhinoceratoidea, 
gen. 
et 
sp. 
indet. 
Protoreodon 
petersoni 
Agriochoerusmaximus 
Bathygenysa!fa* 
Merycoidodontidae, 
gen. 
et 
sp. 
indet. 
Hypertragulus 
heikeni 
cf. 
Leptomeryx 
sp. 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
Ferrusquia-V 
1969 
‘Probably 
B. 
reevesi 


More 
recently, 
several 
dates 
have 
been 
run 
byParker 
(1976) 
and 
Parker 
and 
McDowell 
(1973, 
and 
in 
press) 
for 
igneous 
rocks 
in 
the 
northern 
Davis 
and 
Barilla 
Mountains 
(fig. 
3, 
table 
15). 
The 
igneous 
rocks 
dated 
by 
Parker 
and 
McDowell 
overlie 
the 
Huelster 
Formation 
from 
which 
came 
the 
Hyracodon 
tooth, 
TMM 
41256-4, 
collected 
by 
C. 
L. 
Baker, 
identified 
by 
R. 
L. 
Stirton, 
and 
mentioned 
first 
in 
Sellards 
(1933). 
Baker 
also 
collected 
a 
flora 
from 
the 
Huelster 
Formation 
that 
was 
described 
by 
Berry 
(1919) 
and 
recently 
reviewed 
by 
Axelrod 
and 
Bailey 
(1975). 
Hyracodon 
is 
usually 
considered 
an 
Oligoceneform 
and 
is 
found 
in 
the 
Porvenir 
l.f. 
in 
the 
Vieja 
area. 
This 
adds 
support 
to 
the 
proposal

in 
Wilson 
et 
al. 
(1968) 
that 
a 
date 
of 
38.6 
for 
the 
age 
of 
the 
Buckshot 
Ignimbrite 
is 
the 
most 
logical 
of 
the 
ones 
presented 
for 
the 
base 
of 
the 
Oligocene.

The 
oldest 
igneous 
flow 
rocks 
of 
the 
Tertiary 
are 
in 
the 
Canoe 
Formation 
(Bridgerian)
in 
Big 
Bend 
National 
Park 
but 
in 
spite 
of 
several 
attempts 
no 
samples 
suitable 
for 
datinghave 
been 
collected. 
The 
earliest 
date 
in 
the 
Big 
Bend 
area 
(47 
m.y.) 
is 
on 
a 
tuff 
that 
directly 
underlies 
a 
very 
early 
Uintan 
Whistler 
Squat 
l.f. 
of 
the 
Agua 
Fria 
area 
that 
is 
in 
turn 
overlain, 
but 
not 
directly, 
by 
a 
biotite 
rich 


tuff 
dated 
at 
42.9 
m.y. 
These 
dates 
correlate 
closely 
with 
41.2 
± 
1.4 
given 
by 
Black 
(1969) 
for 
tuffs 
associated 
with 
vertebrate 
faunas 
of 
Uintan 
age 
in 
the 
Badwater 
area, 
Wyoming.
The 
Texas 
dates 
correlate 
closely 
with 
those 


given 
by 
Mauger 
(undated 
report) 
for 
Utah 
and 
Wyoming 
and 
are 
certainly 
additional 
evidence 
to 
support 
the 
proposed 
recalibration 
of 
the 
Eocene 
by 
McKenna 
et 
al. 
(1973). 
More 
data 
on 
these 
dates 
will 
be 
given 
in 
Part 
II 
of 
this 
report. 


The 
dates 
recently 
run 
by 
Parker 
and 
McDowell 
(1973 
and 
in 
press) 
on 
the 
volcanic 
rocks 
associated 
with 
vents 
in 
the 
Paisano 
Pass 
area 
and 
Chinati 
Peak 
add 
support 
to 
the 
growing 
mass 
of 
evidence 
that 
volcanic 
activity 
in 
the 
Big 
Bend 
area 
began 
about 
47 


m.y. 
ago, 
reached 
its 
peak 
from 
38-26 
m.y.
and 
gradually 
died 
out 
from 
22-17 
m.y. 
ago. 
Biochronology 


Candelaria 
Local 
Fauna-Table 
14 
shows 
the 
stratigraphic 
distribution 
of 
the 
currentlyidentified 
taxa 
from 
the 
five 
local 
faunas 
in 
the 
Vieja 
area. 
The 
oldest 
or 
Candelaria 
l.f. 
is 
not 
large 
in 
terms 
of 
specimens 
and 
taxa 
but 
is 
composed 
of 
a 
new 
association 
of 
taxa. 
Prolapsus 
is 
now 
known 
in 
the 
Candalaria 
l.f. 
whereas 
it 
was 
first 
discovered 
in 
the 
AguaFria 
area 
(Part 
11, 
this 
study) 
and 
was 
identified 
by 
Wood 
(1973). 
In 
the 
Agua 
Fria 
area 
it 
is 
associated 
with 
a 
rodent 
fauna 
that 
Wood 
(1973) 
dated 
as 
Bridgerian, 
so 
it 
is 
now 
known 
to 
extend 
from 
the 
Whistler 
Squat 
l.f. 
to 
the 
Candelaria 
l.f. 
Manitsha 
extends 
from 
the 
Candelaria 
through 
the 
Porvenir 
to 
the 
Little 
Egypt 
local 
faunas. 
It 
was 
previouslyknown 
only 
from 
the 
Brule 
Formation 
of 
the 
Slim 
Buttes 
area 
of 
South 
Dakota; 
however,
the 
locality 
and 
age 
of 
the 
type 
is 
uncertain 
(Lillegraven 
1970). 
Leptotomus 
leptodus, 
late 
Eocene 
in 
Utah, 
is 
present 
in 
the 
Candelaria 


l.f. 
and 
with 
Harpago/estesEpihippus, 
Sthen,


odectes; 
Protoreodon 
petersoni, 
and 
Leptore


odon 
marshi 
certainly 
form 
a 
late 
Eocene 
as


sociation. 
The 
work 
in 
progress 
by 
Schiebout 


on 
Dilophodon 
and 
Colodon 
cf. 
hancocki 


do 
not 
contradict 
this 
conclusion. 


The 
40 
m.y. 
date 
from 
the 
stratigraphically 


24 



lower 
Gill 
Breccia 
means 
that 
the 
Candelaria 


l.f. 
is 
approximately 
that 
old 
(Wilson 
et 
al. 
1968). 
The 
date 
of 
39.3 
by 
McDowell 
et 
al. 
(1973) 
for 
an 
ashy 
siltstone 
at 
the 
contact 
of 
the 
Halfway 
and 
Lapoint 
members 
of 
the 
Duchesne 
River 
Formation 
would 
place 
the 
Halfway 
l.f. 
in 
the 
late 
Eocene. 
Epihippus 
intermedius 
is 
the 
only 
taxon 
in 
the 
Halfway 
1. 
f. 
known 
elsewhere, 
and 
according 
to 
Forsten 
(1971a), 
"The 
measurements 
on 
P4-M2 
from 
the 
Candelaria 
l.f. 
fall 
among 
the 
observations 
on 
the 
hypodigm 
of 
E. 
gracilis, 
and 
in 
size 
to 
a 
group 
consisting 
of 
material 
of 
that 
species 
and 
of 
E. 
intermedius." 
This 
correlation 
partly 
supports 
the 
interpretation 
givenby 
McKenna 
et 
al. 
(1973) 
in 
which 
the 
Brennan 
Basin 
(Randlett) 
and 
Dry 
Gulch 
Creek 
(Halfway) 
Member 
and 
the 
Candelaria 
l.f. 
are 
placed 
in 
the 
Eocene. 
The 
most 
common 
form 
in 
the 
Candelaria 


l.f. 
is 
Protoreodon 
petersoni; 
followed 
by 
Epihippus. 
Less 
common 
are 
Protoreodon 
pumiius 
and 
Leptogragaius, 
with 
other 
taxa 
known 
only 
from 
single 
specimens.
Last 
appearances 
in 
the 
Candelaria 
l.f. 
in 
the 
lower 
sorted 
facies 
include 
Harpagolestes,
Epihippus, 
Di/ophodon, 
and 
Leptoreodon, 
whereas 
Prolapsus 
makes 
its 
last 
appearancein 
the 
upper 
glass 
facies. 


Toromeryx 
is 
an 
endemic 
form 
perhaps 
ancestral 
to 
Heteromeryx. 


Porvenir 
Local 
Fauna 
This 
unit 
contains 
the 
largest 
assemblage 
of 
taxa 
in 
the 
Vieja 
area 
and 
is 
the 
only 
one 
usually 
referred 
to 
in 
older 
literature 
as 
the 
"Vieja 
Fauna." 
The 
discovery 
of 
a 
succession 
of 
local 
faunas 
in 
stratigraphic 
superposition 
necessitated 
the 
assignment 
of 
local 
fauna 
names 
to 
collections 
made 
within 
limited 
stratigraphic 
intervals. 
Thus, 
the 
Porvenir 
l.f. 
includes 
forms 
found 
in 
the 
Chambers 
Tuff 
above 
the 
Buckshot 
Ignimbrite 
and 
below 
the 
upper 
marker 
bed. 
The 
assemblage 
has 
the 
association 
of 
Mesohippus 
with 
Protoreodon 
and 
Poabromylus, 
which, 
although 
now 
known 
to 
occur 
in 
other 
Chadronian 
faunas, 
was 
first 
recognized 
by 
Wilson 
(1971a, 
1974).Perhaps 
more 
significant, 
however, 
is 
the 
association 
of 
Hemipsalodon, 
Brachyhyops, 
and 
a 
primitive 


species 
of 
Leptomeryx. 
Such 
an 
association 
occurs 
within 
the 
"Lower 
banded 
zone" 
of 
the 
Little 
Lone 
Tree 
Gulch 
sections 
at 
Flagstaff 
Rim, 
Wyoming 
(Emry, 
pers. 
com., 
and 
Emry 
1973). 


The 
lower 
limit 
of 
sedimentary 
rocks 
of 
the 
Chambers 
Tuff 
and 
the 
limit 
of 
the 
possibilityof 
finding 
members 
of 
the 
Porvenir 
l.f. 
is 
at 
the 
stratigraphic 
contact 
with 
the 
top 
of 
the 
Buckshot 
Ignimbrite. 
The 
first 
appearance,
therefore, 
of 
the 
members 
of 
the 
Porvenir 
l.f. 
is 
the 
result 
of 
the 
beginning 
of 
sedimentaryaccumulation 
following 
a 
local 
volcanic 
eruption 
and 
is 
not 
necessarily 
of 
regional 
significance. 
The 
total 
assemblage 
of 
the 
Porvenir 


l.f. 
enclosed 
by 
potassium-argon 
dates 
is 
regionally 
significant. 
In 
addiition, 
the 
appearance 
of 
new 
taxa 
higher 
in 
the 
section 
and 
the 
order 
of 
their 
appearance 
is 
significant 
although 
the 
proof 
of 
an 
appearance 
as 
"the 
first" 
is 
good 
only 
until 
an 
earlier 
one 
is 
found. 
The 
faunal 
lists 
in 
table 
14 
do 
not 
give 
the 
frequency 
of 
occurrence 
of 
the 
various 
taxa. 
Not 
all 
data 
are 
currently 
at 
hand 
but 
table 
16 
is 
a 
census 
of 
numbers 
of 
specimens 
of 
some 
of 
the 
medium-sized 
herbivores 
in 
the 
Porvenir 
l.f. 
The 
samples 
were 
taken 
independently 
at 
different 
times. 
The 
first 
was 
taken 
by 
Langston, 
McAnulty, 
and 
Savageunder 
Stovall 
in 
1938 
and 
1940 
when 
approximately 
one 
week 
was 
spent 
in 
the 
field; 
the 
second, 
by 
Patterson 
and 
Quinn 
for 
the 
Field 
Museum 
of 
Natural 
History 
when 
three 
months 
were 
spent 
in 
the 
field. 
I 
have 
collected 
from 
the 
same 
area 
for 
a 
total 
time 
of 
approximately 
two 
months 
accompaniedby 
various 
colleagues 
and 
field 
assistants. 
All 
of 
the 
material 
from 
the 
Porvenir 
l.f. 
was 
collected 
by 
surface 
prospecting 
because 
the 
highly 
consolidated 
matrix 
cannot 
be 
washed. 
All 
three 
collections 
show 
a 
similarity 
of 
frequency 
of 
genera 
(I 
do 
not 
have 
figureson 
the 
collection 
of 
Leptomeryx 
at 
the 
FMNH 
but 
know 
it 
to 
be 
larger 
than 
five).

Mesohippus 
and 
Agriochoerus 
are 
by 
far 


the 
most 
common 
genera 
in 
collections 
and 
none 
of 
the 
specimens 
of 
these 
two 
genera 
were 
found 
in 
quarry 
situations. 
Leptomeryxis 
common 
but 
this 
is 
a 
much 
smaller 
form. 


25 



Heteromeryx, 
Protoreodon, 
and 
Poabromylus 
are 
not 
rare 
in 
the 
total 
collection. 
Merycoidodonts, 
on 
the 
other 
hand, 
are 
rare. 
Ac/istomycter 
is 
found 
at 
a 
similar 
stratigraphic 
position 
in 
the 
southern 
Vieja 
area. 


A 
comparison 
with 
Clark 
et 
al. 
(1967, 
fig.
25) 
for 
the 
genera 
of 
the 
Chadron 
Formation 
shows 
that 
Mesohippus 
is 
common 
in 
the 
Ahern 
and 
Crazy 
Johnson 
but 
becomes 
rare 
in 
the 
overlying 
Peanut 
Peak. 
Agriochoerus 
is 
rare 
in 
the 
Ahearn 
and 
Crazy 
Johnson 
and 
not 
known 
but 
probably 
existed 
during 
the 
time 
of 
deposition 
of 
the 
Peanut 
Peak. 
Unfortunately, 
Clark 
et 
al. 
(1967) 
did 
not 
study 
the 
small 
selenodont 
artiodactyls 
from 
the 
Chadron 
Formation 
of 
South 
Dakota. 
Through 
the 
courtesy 
of 
Dr. 
John 
Clark 
I 
was 
able 
to 
examine 
the 
small 
artiodactyls 
from 
the 
Chadron 
Formation 
in 
the 
FMNH. 
To 
describe 
that 
large 
and 
valuable 
collection 
is 
beyond 
the 
scope 
of 
this 
study 
but 
I 
can 
report 
on 
certain 
conclusions 
that 
are 
pertinent 
to 
this 
report. 
I 
hope 
that 
the 
Chicago 
material 
will 
be 
reported 
on 
fully 
in 
the 
not-too 
distant 
future. 
Leptomeryx 
is 
the 
most 
common 
small 
artiodactyl 
in 
the 
FMNH 
collection 
from 
the 
Chadron 
Formation; 
44 
specimens 
were 
borrowed 
and 
this 
was 
not 
all 
of 
the 
Leptomeryx 
specimens 
in 
that 
collection. 
In 
addition, 
37 
partial 
dentitions 
or 
isolated 
teeth 
of 
Poabromylus 
were 
examined. 
Eleven 
specimens 
of 
Poebrotherium, 
two 
specimensof 
Heteromeryx, 
and 
one 
of 
Eoty/opus 
were 
certainly 
identified. 
In 
addition 
and 
very 
important 
were 
three 
specimens 
labeled 
Pentacemylus 
and 
one 
labeled 
PCamelodon. 
A 
comparison 
of 
the 
specimens 
of 
Pentacemyluswith 
casts 
of 
dentitions 
from 
the 
Myton 
of 
Utah 
showed 
no 
difference. 
Pentacemylus 
is 
now 
known 
from 
the 
Myton, 
is 
listed 
by 
Andersen 
and 
Picard 
(1972) 
from 
the 
Lapoint,
and 
is 
also 
present 
in 
the 
Chadron 
Formation. 
The 
specimens 
so 
identified 
are 
FMNH 
PM 
22760, 
P4-M2; 
22759, 
M3; 
22758, 
7P2-P3


The 
specimen 
number 
of 
the 
PCamelodon 
is 
FMNH 
PM 
22754. 
More 
detailed 
work 
is 
needed 
on 
the 
small 
artiodactyls 
of 
the 
Chadron 
Formation 
of 
South 
Dakota 
and 
my 
only 
purpose 
here 
is 
to 
point 
out 
their 
presence 
in 
the 
northern 
fauna. 


Nonetheless, 
the 
data 
in 
tables 
14 
and 
16 
are 
useful 
for 
interpreting 
faunal 
succession 
and 
with 
the 
control 
of 
potassium-argon 
dates 
it 
is 
possible 
to 
draw 
preliminary 
conclusions. 
The 
date 
of 
38.6 
m.y. 
for 
the 
Buckshot 
Ignimbrite 
beneath 
the 
Porvenir 
l.f. 
and 
the 
large 
number 
of 
dates 
run 
by 
Parker 
and 
McDowell 
given 
in 
table 
16 
and 
the 
36.5 
date 
on 
the 
Bracks 
Rhyolite 
bracket 
the 
time 
spanof 
the 
Porvenir 
l.f. 
In 
this 
interval 
the 
most 
commonly 
found 
medium-sized 
herbivores 
in 
Texas 
are 
Mesohippus 
and 
Agriochoerus. 
Beneath 
the 
Buckshot 
Ignimbrite 
ii 
the 
Col


/

mena 
Tuff 
and 
beneath 
it 
the 
Gill 
Breccia. 


volcanic 
rock 
from 
the 
Gill 
Breccia 
was 
dated 
at 
40 
m.y. 
(Wilson 
et 
al. 
1968). 
This 
brackets 
the 
Candelaria 
l.f. 
between 
40 
and 
38 
m.y. 
The 
most 
commonly 
found 
herbivores 
in 
the 
Candelaria 
l.f. 
are 
Protoreodon 
(13 
specimens) 
and 
Epihippus 
(four 
specimens). 


This 
succession 
agrees 
in 
part 
with 
Clark 
et 
al. 
(1967, 
fig. 
24). 
They 
list 
an 
association 
of 
Mesohippus 
and 
Agriochoerus 
overlying 
Epihippus, 
Diplobunops, 
and 
Poabromylus. 
They 
also 
include 
Te/eodus 
but 
the 
titanotheres 
from 
this 
part 
of 
the 
section 
are 
sorely 
in 
need 
of 
restudy. 
Clark 
et 
al. 
(1967) 
also 
include 
Diplobunops 
and 
Poabromylus 
as 
associates 
in 
the 
"index 
fauna" 
with 
Teleodus 
and 
Epihippus. 
Diplobunops 
has 
not 
yetbeen 
found 
in 
Texas, 
so 
its 
association 
cannot 
be 
verified. 
It 
may 
be 
that 
Diplobunops 
either 
did 
not 
inhabit 
the 
Texas 
area 
or 
that 
Diplobunops 
was 
present 
in 
an 
earlier 
association 
not 
found 
in 
the 
Vieja 
area. 
Poabromylus, 
on 
the 
other 
hand, 
is 
present 
in 
Texas 
and 
is 
now 
known 
from 
the 
Lapoint 
and 
the 
Chadronian, 
so 
is 
not 
a 
useful 
part 
of 
an 
"index 
fauna" 
to 
identify 
the 
early 
Duchesnean 
of 
Clark 
et 
al. 


(1967, 
fig. 
24).

McDowell 
et 
al. 
(1973) 
give 
a 
date 
of 


36.3 
± 
0.7 
for 
an 
unnamed 
tuff 
three 
feet 
below 
the 
top 
of 
the 
Ahearn 
Member 
of 
the 
Chadron 
Formation. 
This 
date 
correlates 
as 
closely 
as 
can 
be 
expected 
with 
the 
dates 
of 
36.8 
and 
36.5 
± 
1.2 
for 
the 
Bracks 
Rhyolitethat 
overlies 
the 
Chambers 
Tuff. 
Ash 
B 
of 
the 
Flagstaff 
Rim 
section 
lies 
above 
the 
occurrence 
of 
Brachyhyops 
and 
Hemipsalodonand 
was 
dated 
by 
Evernden 
et 
al. 
(1964) 
as 
26 



Table 
14.—Stratigraphic 
occurrence 
of 
currently 
identified 
taxa 
in 
the 
local 
faunal 
succession 
of 
theVieja 
area. 
Figures 
representpotassium/argon 
dates 
that 
show 
the 
best 
fit 
to 
the 
superposition 
and 
composition 
of 
the 
faunas. 
40.0 
is 
from 
a 
boulder 
within 
the 
Gill 
Breccia 
stratigraphically 
beneath 
the 
Candelaria 
l.f. 
(Wilson 
et 
al. 
1968); 
38.6 
is 
from 
the 
Buckshot 
Ignimbrite 
(Wilson 
etal. 
1968);36.8isfromtheBracksRhyolite(Wilsonetal. 
1968);31.4isthecurrentlyacceptedaveragedatefortheBrite 
Ignimbrite 
which 
is 
the 
equivalent 
of 
the 
Mitchel 
Mesa 
Rhyolite 
to 
the 
south 
(McDowell, 
personal 
communication 
1977). 
Taxa 
of 
certain 
identification 
in 
the 
Rancho 
Gaitan 
l.f. 
are 
shown 
as 
G, 
although 
their 
position 
with 
respect 
to 
the 
date 
on 
the 
Bracks 


is 
based 
on 
correlation 
only. 
Position 
of 
the 
Ash 
Spring 
l.f. 
is 
based 
on 
evolutionary 
position 
of 
taxa. 
Carnivora 
by 
Gustafson 
(in 
progress); 
Ceratomorpha 
by 
Schiebout 
(in 
progress). 
G 
is 
Rancho 
Gaitan. 


TAXA 


K-Ar 
dates: 
40.0 


MARSUPALIA 


?Peratherium 
sp. 


INSECTIVORA 


Geolabis 
n. 
sp.
Lepictis 
douglasiLeptictis 
wilsoni 
Apternodus 
cf. 
brevirostris 


PRIMATES 


Omomyid 
gen. 
et 
sp. 
indet. 
Rooneyia 
viejaensis 


RODENTIA 


Leptotomus 
leptodus

L. 
gigansMytonomys 
gaitaniaMicroparamys 
perfossusIschyrotomus 
cf. 
/. 
petersoniManitshajoahniculiIschryomys 
blacki 
Titanotheriomys 
veterior 
Cylindrodon 
fontis 
PseudocylindrodonneglectusPseudocylindrodon 
cf. 
neglectus
P. 
texanus 
P. 
cf. 
texanus 
Ardynomys 
occidentalis 
Jaywilsonomysojinagaensis

J. 
pintoensis
J. 
aff. 
pintoensisAdjidaumo 
cf. 
A. 
minutus 
Viejadjidaumo 
magniscopulicf. 
Viejadjidaumo 
sp. 
indet. 
Aulolithomysbounites 
A. 
cf. 
A. 
bounites 
FAUNAS 


38.6 
36.8 
31.4 
Candelaria 
l.f. 
Porvenir 
l.f. 
Little 
Egypt 
l.f. 
Airstrip 
l.f. 
Ash 
Spring 
l.f. 


X 


X 
X 
X 
X 


X 
X 


X 
X 


G 
X 
X 


XX 
X 


X 
XX 
X 
XX 
X 
XX 


X 
G 
G 


X 
X 
X 
X 


X 
X 


[Table 
14 
continued, 
next 
page] 


27 



[Table 
14, 
continued] 


TAX 
A 
FAUNAS 


K-Ar 
dates: 
40.0 
38.6 
36.8 
31.4 


Candelaria 
l.f. 
Porvenir 
1.f. 
Little 
Egypt 
l.f. 
Airstrip 
l.f. 
Ash 
Spring 
l.f. 


Meliakrouniomys 
wilsoni 
X 
Yoderimyslustrorum 
X 
Eutypomys 
inexpectatus 
X 
X 
cf.eutypomyidgen.etsp.indet 
X 
cf. 
Simimys 
sp. 
indet. 
X 
Subsumus 
candelariae 
X 
Prolapsus 
sp. 
X 


CARNIVORA 


Harpagolestes 
sp. 
X 
Ischnognathussavagei 
X 
Hemipsalodon 
n. 
sp. 
X 
Hyaenodon 
sp. 
X 
X 
X 
Miacis 
n. 
sp. 
X 
X 
Daphoenus 
sp. 
X 
Daphaenocyon 
sp. 
X 
Hesperocyon 
sp. 
X 
Fetid 
gen. 
et 
sp. 
indet. 


PER 
ISSODACTYLA 


Epihippus 
cf. 
E. 
gracilis 
X 


Haplohippus 
texanus 
X 


Mesohippustexanus 
X 


Mesohippussp. 
X 


PSthenodectesaustralis 
X 


Menodus 
bakeri 
X 
X 


Teleodussp. 
X 


Dilophodon 
n. 
sp. 
X 


Colodon 
cf. 
hancocki 
X 


Colodon 
n. 
sp. 
X 
X 


Hyracodon 
sp. 
X 
X 
X 


Amynodon 
sp. 
X 


Megamynodon 
sp. 
X 


Caenopus 
sp. 
X 


Schizotheroides 
jackwilsoni 
X 
X 


Toxotherium 
cf. 
T. 
woodi 
X 


ARTIODACTYLA 


Brachyhops 
wyomingensis 
X 
Archaeotherium 
cf. 
A. 
mortoni 
X 
X 
X 
Protoreodon 
petersoni 
X 
G 


P. 
pumiius 
X 
X 
Agriochoerus 
antiques 
X 
X 


A. 
maximus 


G 
Bathygenys 
reevesi 
XG 


Aclistomyctermiddletoni 
X 


[Table 
14 
continued, 
next 
page] 


28 



[ 
Table 
14, 
continued] 


TAX 
A 
FAUNAS 


K-Ar 
dates: 
40.0 
38.6 
36.8 
31.4 


Candelaria 
l.f. 
Porvenir 
l.f. 
Little 
Egypt 
l.f. 
Airstrip 
l.f. 
Ash 
Spring 
l.f. 


X

Merycoidodontidaegen. 
et 
sp. 
indet. 
X 
G 


Merycoidodon 
dunagani 
X 
Limnenetes 
cf. 
L. 
platyceps 
X 
PProdesmatochoerus 
meekae 
X 
Leptoreodonmarshi 
X 
Poabromyluskayi 
X 


P. 
minor 
X 
Toromeryx 
marginatus 
X 
Heteromeryx 
dispar 
X 
Oromeryx 
sp. 
X 
Oromerycinae 
gen. 
et 
sp. 
indet. 
X 
Eotylopus 
cf. 
E. 
reedi 
Hidrosotherium 
transpecoensis 
X 
Poebrotherium 
franki 
X 
X 
Poebrotherium 
sp. 
X 
Hypertragulusheikeni 
G 
Leptomeryx 
defordi 
X 
Hypisodus 
cf. 
H. 
minimus 
X 
X 


35.2 
and 
33.3 
m.y. 
Correlations 
with 
this 
span 
are 
perhaps 
as 
close 
as 
can 
be 
hoped 
for 
with 
our 
present 
tools. 
Last 
appearances 
within 
the 
Porvenir 
l.f. 
are 
important. 
Schizotheroides 
is 
only 
known 
elsewhere 
from 
the 
Sage 
Creek 
Eocene 
of 
Montana. 
Protoreodon 
first 
appears 
in 
Uinta 
B 
in 
Utah 
and 
survives 
until 
the 
early 
Chadronian 
Porvenir 
l.f. 
Although 
the 
specimen 
is 
very 
fragmentary, 
Oromeryx 
is 
present 
in 
the 
Porvenir 
l.f. 
and 
is 
another 
survivor 
from 


Uinta 
B. 


The 
only 
presently 
known 
endemic 
forms 
seem 
to 
be 
Rooneyia, 
Haplohippus, 
Aclistomycter, 
and 
Hidrosotherium. 
Ischnognathus, 
in 
my 
opinion, 
is 
indeterminate. 
All 
other 
genera 
have 
been 
identified 
elsewhere. 


The 
succession 
of 
appearance 
of 
genera 
within 
the 
family 
Merycoidodontidae 
in 
the 
Vieja 
area 
is 
interesting. 
Merycoidodonts 
in 
the 
Porvenir 
l.f. 
are 
known 
only 
from 
a 
few 
indeterminate 
fragments 
from 
the 
Big 
Cliff 
area. 
In 
the 
southern 
area 
near 
Adobe 
Spring,
remains 
of 
Aclistomycter 
are 
found 
in 
an 
interval 
25-40 
feet 
above 
the 
Buckshot 
Ignim


brite 
but 
still 
beneath 
the 
lower 
marker 
bed. 
This 
is 
the 
lowest 
occurrence 
of 
an 
identifiable 
merycoidodont. 
In 
the 
overlying 
Little 
Egypt 
l.f. 
in 
the 
upper 
part 
of 
the 
Chambers 
Tuff 
about 
60 
feet 
below 
the 
Bracks 
Rhyolite, 
Merydoidon 
dunagani 
and 
Bathygenysreevesi 
are 
common. 
Limnenetes 
and 
PProdesmatochoerus 
appear 
in 
the 
Airstrip 
l.f. 


570 
feet 
above 
the 
Bracks 
Rhyolite 
in 
the 
Capote 
Mountain 
Tuff. 


The 
following 
are 
members 
of 
the 
Flagstaff 
Rim 
fauna 
as 
listed 
by 
Emry 
(1973)
that 
are 
absent 
from 
the 
Porvenir 
l.f. 
A 
microfauna 
cannot 
be 
obtained 
by 
washingfrom 
the 
Chambers 
because 
of 
sediment 
consolidation, 
but 
a 
surprising 
number 
of 
insectivores, 
rodents, 
and 
the 
primate 
are 
known 
from 
skulls 
or 
jaw 
fragments. 
Peratherium 
is 
absent 
but 
I 
suspect 
this 
is 
an 
accident 
of 
collecting. 
The 
apatemyid 
Sinclairella 
and 
the 
Orders 
Chiroptera 
and 
Pholidata 
are 
absent. 
The 
family 
Castoridae 
and 
the 
order 
Lagomorpha 
also 
are 
absent. 
The 
carnivores, 
tapirs, 
and 
rhinos 
are 
still 
being 
studied 
so 
I 
do 
not 
wish 
to 
comment 


29 



beyond 
listing 
them 
in 
table 
14. 
The 
families 
Leptochoeridae 
and 
Anthracotheriidae 
are 
not 
present 
in 
the 
Texas 
fauna. 


It 
is 
difficult 
to 
assess 
the 
significance 
of 


the 
absence 
of 
certain 
taxa 
in 
faunal 
lists. 
Their 
absence 
may 
be 
for 
a 
number 
of 
reasons: 
geographic 
distribution, 
temporal 
distribution, 
the 
accessibility 
of 
microfaunas,
and 
length 
of 
time 
of 
collecting. 
Nonetheless, 
certain 
groups 
are 
conspicuous 
by 
their 
absence 
from 
the 
Porvenir 
l.f. 
No 
lagomorphhas 
been 
found 
in 
the 
Porvenir 
l.f. 
nor 
has 
anylagomorph 
been 
found 
in 
any 
west 
Texas 
fauna 
prior 
to 
the 
Arikareean. 
During 
20 
yearsof 
collecting 
it 
would 
be 
reasonable 
for 
one 
to 
assume 
that 
lagomorphs 
would 
have 
been 
discovered 
if 
they 
were 
present. 
Similarly, 
no 
pholidotan, 
leptochoerid, 
nor 
anthracothere 
has 
been 
found 
in 
west 
Texas. 
Like 
the 
lagomorphs, 
I 
would 
have 
thought 
they 
would 


have 
been 
found 
by 
now 
if 
they 
had 
been 


present. 
Although 
this 
is 
based 
on 
negative

evidence 
I 
believe 
they 
were 
not 
present 
be


cause 
of 
geographic 
distribution. 


Taxa 
that 
are 
present 
in 
the 
Porvenir 
l.f. 


but 
absent 
at 
Flagstaff 
Rim 
according 
to 
the 


preliminary 
list 
of 
Emry 
(1973) 
are 
the 
tar


si 
iform 
Rooneyia, 
Leptotomus, 
Micropara


mys, 
Ischryotomus, 
Manitsha, 
Pseudocylin


drodon, 
Ardynomys, 
Viejadjidaumo, 
Au/o


lithomys, 
Yoderimys, 
Eutypomys, 
cf. 
Simi


mys, 
Haplohippus, 
Schizotheroides, 
Protoreo


don 
Heteromeryx, 
Aclistomycter, 
and 
Hidro


f 


sotherium. 
Of 
these, 
Leptotomus, 
Microparamys, 
and 
Manitsha 
are 
also 
present 
in 
the 
late 
Eocene 
as 
are 
Schizotheroides 
and 
Protoreodon. 
The 
latter 
five 
genera 
may 
represent 
a 
difference 
in 
temporal 
distribution 
and 
signify 
a 
slightly 
earlier 
age 
for 
the 
Porvenir 
or 
perhaps 
represent 
a 
geographic 
difference. 
I 
prefer 
the 
former 
because 
of 
the 
slight 
difference 
in 
potassium-argon 
dates. 


More 
important 
are 
the 
genera 
held 
in 
common, 
the 
most 
significant 
of 
which 
I 
believe 
to 
be 
Meliakrouniomys, 
Hemipsaiodon, 
Toxotherium, 
Brachyhyops, 
Eotylopus, 
and 
a 
small 
oromerycid. 
On 
the 
basis 
of 
these 
and 
other 
genera 
held 
in 
common, 
the 
lower 
part 
of 
the 
Flagstaff 
Rim 
and 
the 
Porvenir 
faunas 
are 
both 
early 
Chadronian. 


Table 
15. 
Distribution 
of 
K-Ar 
dates 
in 
the 
Vieja 
area 
and 
northern 
Davis 
Mountains. 


1. 
40.0 
± 
2.0, 
boulder 
in 
Gill 
Breccia. 
Gives 
lower 
limit 
for 
Colmena 
Tuff 
and 
Candelaria 
l.f. 
(Wilson 
et 
al. 
1968). 
2. 
38.6 
± 
1.2,BuckshotIgnimbrite. 
Givesupperlimitfor 
Colmena 
Tuff 
and 
Candelaria 
l.f. 
and 
lower 
limit 
for 
Chambers 
Tuff 
and 
Porvenir 
l.f. 
(Wilson 
et 
al. 
1968). 


3. 
37.2 
± 
0.7 
Star 
Mt. 
Rhyolite 
and 
36.6 
0.7 
Gomez 
Ash-Flow 
sheet 
(ave 
of 
6 
dates)
± 


±

37.1 
0.4 
Adobe 
Canyon 
Fm. 
(ave 
of 
2 
dates) 
36.2 
± 
0.4 
Sleeping 
Lion 
Fm. 
(ave 
of 
2 
dates) 
35.6 
± 
0.3 
Barrel 
Springs 
Fm. 
(ave 
of 
2 
dates) 
±

36.8 
0.7 
Goat 
Canyon 
Trachyte 
all 
give 
upper 
date 
for 
Huelster 
Fm. 
with 
Hyracodon 
(all 
in 
Parker 
and 
McDowell, 
in 
press).

4. 
36.5 
± 
1.2 
and 
36.8 
Bracks 
Rhyolite. 
Gives 
upper 
date 
for 
Porvenir 
l.f.(Wilson 
et 
al. 
1968). 
5. 
31.4 
± 
0.5 
Mitchell 
MesaRhyolite 
Tuff 
(=Brite 
Ignimbrite) 
average 
of 
five 
dates 
(pers. 
com. 
F. 
W. 
McDowell 
Sept. 
21, 
1976). 
This 
is 
the 
most 
widespread 
igneous 
unit 
in 
Trans-Pecos 
Texas. 
It 
is 
an 
upper 
date 
for 
the 
Airstrip 
l.f. 
in 
the 
Vieja 
area. 


6. 
22.3and 
19.2averageagesonolderandyoungerdike 
swarm 
in 
the 
Vieja 
area. 
Dasch 
et 
al. 
1969. 
Little 
Egypt 
Local 
Fauna 
—Most 
of 
the 
material 
that 
makes 
up 
this 
local 
fauna 
comes 
from 
two 
general 
localities. 
The 
most 
prolific.
Reeves 
Bonebed, 
occurs 
approximately 
30 
feet 
below 
the 
upper 
marker 
bed 
in 
the 
Chambers 
Tuff. 
The 
other 
area 
is 
known 
as 
Chalk 
Gap 
Draw. 
The 
fauna 
contains 
the 
highest 
occurrence 
of 
Manitsha 
in 
the 
Vieja 
area. 
The 
other 
rodents 
indicate 
a 
correlation 
with 
Pipestone 
Springs, 
Montana. 
The 
presence 
of 
Bathygenys 
in 
both 
faunas 
supports 
this 
conclusion. 
Limnenetes 
is 
associated 
with 
Bathygenys, 
however, 
in 
the 
overlying 
Airstrip 
l.f. 
and 
although 
the 
faunas 
are 
separated 
by 
almost 
600 
feet 
of 
stratigraphic 
section, 
the 
time 
interval 
is 
apparently 
short. 
The 
presenceof 
the 
small 
species 
of 
Hyaenodon 
similar 
to 
those 
from 
Pipestone 
Springs 
in 
the 
Airstrip

l.f. 
supports 
the 
same 
conclusion. 
Airstrip 
Local 
Fauna 
This 
fauna 
marksthe 
first 
occurrence 
of 
Poebrotherium, 
Limnenetes, 
PProdesmatochoerus, 
and 
Hypisodusin 
the 
Vieja 
area. 
Limnenetes 
is 
the 
commonform, 
in 
this 
local 
fauna 
followed 
by 
Poebrotherium, 
Bathygenys, 
and 
Hyaenodon. 


30 



Rancho 
Gaitan 
Local 
Fauna 
-Wood 
(1974) 
states 
that 
"the 
three 
rodents 
of 
the 
Rancho 
Gaitan 
local 
fauna 
do 
not 
fit 
in 
with 
any 
of 
the 
other 
Vieja 
local 
faunas" 
and 
suggests 
that 
the 
Rancho 
Gaitan 
l.f. 
falls 
on 
the 
Eocene-Oligocene 
boundary. 
The 
presence 
of 
Bathygenys 
and 
a 
medium-size 
oreodont, 
however, 
led 
Ferrusquia-V 
to 
correlate 
it 
with 
the 
Little 
Egypt 
l.f. 
Also, 
the 
association 
of 
Bathygenysand 
Agriochoerus 
maximus 
is 
known 
in 
the 
Pipestone 
Springs 
fauna 
of 
Montana 
and 
supports 
a 
somewhat 
later 
correlation. 
Hyper


tragulus 
heikeni, 
according 
to 
Ferrusquia-V., 
is 
an 
intermediate 
between 
Simimeryx 
hudsoni 
from 
the 
Pearson 
Ranch 
l.f. 
of 
California 
and 
Hypertragulus 
calcaratus 
and 
is 
slightly 
more 
advanced 
than 
the 
former. 
Ferrusquia-
V. 
(1967) 
and 
Wood 
(1974) 
point 
out 
the 
intermediate 
position 
of 
Jaywilsonomys 
to 
Pareumys 
from 
the 
Hartman 
Ranch 
l.f. 
and 
Sespemys 
of 
the 
late 
Oligocene. 
In 
short,
I 
support 
Ferrusquia-V. 
in 
correlating 
the 
Rancho 
Gaitan 
l.f. 
as 
a 
whole 
with 
the 
Little 
Egypt 
l.f. 
and 
both 
in 
turn 
with 
Pipestone 
Springs, 
Montana. 


Paleoenvironment 


The 
Vieja 
Group 
is 
a 
succession 
of 
voicaniclastic 
sediments 
intercalated 
between 
flow 
rocks 
and 
ignimbrites. 
The 
Gill 
Breccia 
is 
a 
flow 
breccia, 
perhaps 
consisting 
of 
several 
flows. 
Its 
source 
lay 
to 
the 
south 
or 
southwest 
according 
to 
Walton 
(1972) 
and 
was 
probably 
not 
far 
away. 
In 
places 
a 
smooth 
erosion 
surface 
can 
be 
seen 
at 
the 
top 
of 
the 
Gill. 
The 
lower 
or 
sedimentary 
facies 
of 
the 
Colmena 
consists 
of 
sorted 
sandstone, 
described 
by 
Walton 
(1972) 
as 
a 
volcanic 
litharenite. 
Cross-bedding 
is 
found 
in 
the 
lower 
facies 
and 
suggests 
braided 
stream 
deposits.
Gastropod 
steinkerns 
are 
common 
and 
a 
few 
plant 
impressions 
have 
been 
found 
in 
this 
facies. 
Fragments 
of 
crocodile 
or 
alligator 
are 
present 
but 
not 
common. 
The 
area 
near 
the 
mouth 
of 
Capote 
Creek 
during 
the 
time 
of 
accumulation 
of 
the 
lower 
facies 
was 
a 
broad 
valley 
occupied 
by 
braided 
streams 
that 
flowed 
between 
active 
volcanoes. 
Volcanic 
activity 
was 
closer 
during 
the 
time 
of 
the 
ac-

Table 
16.Numbersofspecimensofmediumsizedherbivores, 
Porvenir 
l.f. 


FMNH 
TMM 
OU 
TOTAL 
MesohippusAgriochoerusLep 
tomeryxHeteromeryxProtoreodon 
36 
31 
5+ 
7 
3 
37 
26 
27 
5 
8 
0 
6 
6 
0 
0 
81 
63 
38+ 
12 
11 
PoabromylusAclistomycterMerycoidodontidae 
HaplohippusBrachyhyopsArchaecotherium 
7 
0 
1 
2 
1 
1 
5 
6 
1 
0 
0 
0 
2 
0 
0 
0 
0 
0 
7 
6 
2 
2 
1 
1 
Schizotheroides 
0 
1 
0 
1 
Oromeryx 
0 
1 
0 
1 


cumulation 
of 
the 
lahars 
and 
the 
upper 
glassfacies. 
The 
latter 
is 
the 
result 
of 
nearby 
explosive 
volcanic 
activity. 
Shards 
and 
pumiceform 
most 
of 
the 
matrix. 
Sedimentary 
structures 
are 
very 
rare. 
Only 
one 
concentration 
of 
bones, 
Clabaugh's 
Bonebed, 
was 
found 
in 
this 
facies. 
The 
environment 
was 
probably 
one 
of 
the 
intermittent 
accumulation 
of 
volcanic 
ash. 
At 
times 
the 
ash 
falls 
may 
have 
temporarilykilled 
off 
the 
lower 
vegetation, 
forcing 
the 
retreat 
of 
the 
animals 
dependent 
on 
it, 
but 
as 
the 
tuffaceous 
soil 
weathered 
the 
plantsquickly 
reestablished 
and 
the 
animals 
returned. 


The 
environment 
in 
the 
Vieja 
area 
duringthe 
time 
of 
accumulation 
of 
the 
Chambers 
Tuff 
was 
more 
tranquil. 
Coarse 
conglomeratescontain 
cobble-sized 
material 
of 
reworked 
Cretaceous 
limestone 
that 
came 
from 
the 
Laramide 
folded 
uplands 
to 
the 
west 
in 
Mexico. 
These 
channel 
sandstones 
and 
conglomerates 
often 
contain 
bone 
and 
tooth 
fragments. 
At 
a 
locality 
known 
as 
"red 
mound" 
one 
of 
these 
channels 
grades 
laterally 
into 
a 
bright 
red 
mudstone 
that 
probably 
representsoverbank 
deposits. 
These 
deposits 
contain 
coprolite-shaped 
masses 
with 
bone 
and 
enamel 
chips, 
and 
what 
appear 
to 
be 
burrows. 
Most 
of 
the 
material 
from 
the 
red 
mound 
locality 
consisted 
of 
small 
forms 
(table 
5)
but 
identifiable 
fragments 
of 
larger 
forms 
were 
also 
found. 
Elsewhere 
mudstones 
are 
chocolate 
brown 
and 
light 
brown 
to 
reddish 


31 



brown 
and 
show 
very 
little 
bedding. 
A 
particular 
mudstone 
unit 
may 
be 
from 
a 
few 
inches 
up 
to 
20 
feet 
(16 
m) 
thick. 
These 
show 
very 
little 
bedding 
except 
at 
color 
changes. 
Individual 
bones 
and 
teeth, 
some 
rodent-gnawed, 
are 
widely 
scattered 
in 
a 
dense, 
very 
hard 
mudstone 
but 
no 
articulated 
specimens 
were 
found. 
The 
mudstone 
probably 
represents 
slowly 
accumulating 
volcanic 
ash 
rich 
soils. 
No 
alligator 
or 
crocodile 
remains 
have 
been 
found. 
Turtles 
are 
present

but 
not 
common 
in 
the 
Chambers 
Formation, 
but 
dermal 
scutes 
of 
lizards 
are 
fairly 
common. 


Gastropods 
identified 
as 
Helix 
leidyi 
are 
locally 
common 
in 
both 
the 
Colmena 
and 
Chambers. 
In 
the 
lower 
part 
of 
the 
Chambers,
gastropod 
steinkerns 
three 
inches 
(7.6 
m) 
in 
diameter 
have 
been 
found. 
At 
one 
locality 
near 
Rancho 
Gaitan 
in 
Mexico 
gastropods 
occur 
by 
the 
thousands. 
They 
are 
one 
to 
two 
inches 
at 
their 
widest 
diameter. 


At 
one 
locality 
in 
the 
Chambers 
approximately 
10 
feet 
(3 
m) 
of 
very 
hard 
light 
greentuff 
is 
exposed. 
The 
tuff 
was 
deposited 
as 
a 
mud 
flat 
near 
the 
western 
limit 
of 
the 
Bracks 
Rhyolite. 
It 
may 
be 
in 
either 
the 
top 
of 
the 
Chambers 
or 
the 
base 
of 
the 
Capote 
Mountain. 
Trackways 
are 
found 
at 
several 
levels 
in 
the 
tuff. 
Because 
of 
the 
extreme 
hardness 
and 
lack 
of 
good 
bedding 
it 
was 
beyond 
our 
means 
to 
remove 
them, 
so 
flexible 
molds 
were 
made. 
One 
large 
mold 
about 
9 
by 
18 
feet 
(2.7—5.5 
m) 
contained 
trackways 
of 
a 
variety 
of 
forms. 
One 
was 
of 
a 
bird 
about 
the 
size 
of 
a 
pigeon 
and 
another 
about 
the 
size 
of 
a 
turkey; 
neither 
is 
represented 
by 
skeletal 
material. 
The 
largest 
footprints 
must 
have 
been 
those 
of 
a 
titanothere. 
Two 
trackways 
were 
made 
by 
carnivores, 
one 
large 
that 
could 
belong 
to 
Hyaenodon 
and 
the 
other 
small 
that 
could 
belong 
to 
either 
Daphoenus 
or 
a 
miacid. 
A 
trackway 
of 
medium-size 
clawed 
form 
might 
belong 
to 
Agriochoerus. 
A 
trail 
of 
small 
artiodactyl 
footprints 
is 
the 
right 
size 
for 
Bathygenys. 
Medium-size 
footprints 
with 
three 
distinct 
toes 
are 
either 
tapir 
or 
rhino. 
All 
of 
these 
are 
represented 
on 
the 
largestmold. 
Smaller 
molds 
contain 
the 
trail 
of 
an 
arthropod 
the 
size 
of 
a 
large 
scorpion, 
a 
small 


turtle, 
and 
a 
small 
three-toed 
trackway 
that 
probably 
was 
left 
by 
Mesohippus.

Such 
a 
concentration 
of 
animals 
in 
one 
small 
area 
must 
mean 
that 
it 
was 
close 
to 
a 
watering 
area. 
No 
impressions 
of 
leaves 
are 
seen, 
nor 
was 
there 
any 
petrified 
wood 
nearby. 
It 
may 
be 
that 
the 
area 
was 
part 
of 
a 
broad 
mud 
flat 
adjacent 
to 
a 
river 
or 
intermittent 
stream. 
Raindrop 
impressions 
and 
filled 
mudcracks 
are 
present 
on 
the 
bedding 
surfaces. 
The 
paleoenvironment 
of 
the 
Chambers 
Tuff 
seems 
to 
have 
been 
more 
open 
than 
that 
of 
the 
Colmena, 
more 
removed 
from 
direct 
volcanic 
activity 
and 
probably 
dryer. 


A 
small 
fossil 
flora 
was 
described 
by 
Berry(1919) 
from 
the 
basal 
tuffs 
of 
the 
Huelster 
Formation 
in 
the 
Barilla 
Mountains, 
a 
northeastern 
extension 
of 
the 
northern 
Davis 
Mountains. 
The 
Hyracodon 
tooth 
reported 
on 
pages 
1, 
24 
also 
came 
from 
the 
lower 
tuffs 
of 
the 
Huelster 
Formation. 
The 
Huelster 
is 
correlated 
with 
the 
Chambers 
Tuff 
on 
the 
basis 
of 
the 
K-Ar 
dates 
of 
the 
Bracks 
Rhyolite 
of 
the 
Vieja 
area 
with 
similar 
dates 
on 
the 
Star 
Mountain 
Rhyolite 
(table 
16) 
of 
the 
McCutcheon 
Group 
(Eifler 
1951).

The 
fossil 
flora 
from 
the 
Barilla 
Mountains 
has 
been 
reinterpreted 
by 
Axelrod 
and 
Bailey(1976, 
p. 
237): 


“The 
Barilla 
flora 
has 
the 
fan-palm 
(Saba-
Htes), 
feather-palm 
(Geonomites), 
and 
abundant 
laurel 
(Ocotea, 
recorded 
as 
Oreodaphne), 
evergreen 
holly 
(Hex) 
and 
2 
or 
3 
others 
that 


were 
not 
illustrated, 
including 
a 
reported 
walnut 
(Juglans). 
To 
judge 
from 
the 
small 
sample, 
it 
implies 
a 
warmer 
climate 
than 
the 
Bernalillo 
(New 
Mexico) 
flora 
which 
is 
consistent 
with 
its 
position 
560 
km 
southeast 
and 
probably 
lower 
(300m) 
altitude. 
Representing 
the 
upper 
part 
of 
a 
dry 
mixed 
sub


tropical 
flora 
it 
finds 
analogy 
with 
mixed 
vegetation 
in 
southern 
Tamaulipas 
and 
southward 
along 
the 
east 
front 
of 
the 
Sierra 
Madre 


Oriental." 


Differences 
in 
elevation 
between 
the 
present 
day 
position 
of 
the 
Huelster 
and 
Chambers 
are 
the 
result 
of 
mid-to 
late-Tertiaryfaulting 
but 
during 
the 
early 
Oligocene 
the 


32 



two 
areas 
were 
probably 
close 
to 
the 
same 
elevation. 
In 
both 
areas 
the 
early 
Tertiaryrocks 
lie 
conformably 
on 
late 
Cretaceous. 
In 
the 
Barrillas, 
the 
McCutcheon 
Group 
lies 
on 
marine 
Cretaceous 
correlated 
with 
the 


Taylor 
marl 
of 
central 
Texas; 
in 
the 
Vieja 
area 
the 
Vieja 
Group 
lies 
on 
rocks 
as 
young 
as 
non-marine 
Cretaceous 
beds 
correctable 
with 
the 
Aguja 
and 
Javelina 
Formations 
of 
BigBend 
National 
Park. 
Axelrod 
and 
Bailey'sanalysis 
of 
the 
climate 
for 
the 
Barrilla 
flora 
also 
can 
be 
applied 
to 
the 
climatic 
conditions 
in 
the 
nearby 
Vieja 
area. 


Harris 
(1967a) 
interpreted 
a 
calichification 
of 
the 
tuffaceous 
fossiliferous 
sediment 
at 
Ash 
Spring 
to 
mean 
subarid 
conditions. 
He 
says 
“No 
typical 
caliche 
structures 
were 
seen 
in 
the 
thin 
sections 
but 
the 
preponderance 
of 
sugary 
fine-grained 
calcite 
and 
the 
friable 
nature 
of 
the 
rock 
are 
suggestive 
of 
calichification 
(personal 
communication, 


R. 
L. 
Folk, 
October, 
1966). 
That 
the 
caliche 
was 
implaced 
in 
periods 
of 
subareal 
exposureduring 
the 
accumulation 
of 
the 
rock, 
rather 
than 
subsequently, 
is 
indicated 
by 
thin 
caliche 
beds 
in 
the 
upper 
part 
of 
the 
unit. 
.., 
and 
by 
.“ 


..

pebbles 
of 
caliche 
in 
a 
conglomerate 
. 


The 
Ash 
Spring 
l.f. 
is 
apparently 
the 
youngest

of 
the 
Vieja 
Group 
and 
Harris 
(1967a) 
interpreted 
a 
progressive 
drying 
of 
the 
climate 
in 
the 
Vieja 
area. 


The 
Airstrip 
l.f. 
lived 
on 
the 
periphery 
of 
the 
volcanic 
area 
where 
tuff 
was 
accumulating. 
The 
deposits 
that 
contain 
the 
fossils 
show 
very 
few 
sedimentary 
structures. 
Some 
faint 
cross-bedding 
can 
be 
found 
and 
some 
of 
the 
beds 
fine 
upward 
so 
that 
a 
water 
environment 
for 
deposition 
seems 
certain. 
Turtles 
identified 
as 
Sty/emys 
sp. 
are 
common 
in 
the 
Capote 
Mountain 
whereas 
turtles 
are 
rare 
in 
the 
Chambers. 
Gastropods 
have 
not 
yet 
been 
found 
in 
association 
with 
vertebrates 
in 
the 
Capote 
Mountain. 
The 
Capote 
Mountain 
and 
the 
deposits 
at 
Ash 
Spring 
seem 
to 
have 
been 
laid 
down 
under 
drier 
conditions 
than 
those 
in 
the 
Colmena, 
and 
the 
Chambers 
representsconditions 
somewhat 
in 
between. 
This 
change 
was 
gradual 
over 
a 
period 
of 
six 
to 
eight 
m.y. 


Chronostratigraphy 
and 
the 
Chadronian-Uintan 
Boundary 


Throughout 
this 
report 
I 
have 
used 
the 
terms 
Uintan 
and 
Chadronian, 
avoiding 
use 
of 
the 
term 
Duchesnean. 
All 
three 
terms 
were 
defined 
by 
Wood 
et 
al. 
(1941) 
and 
have 
been 
in 
use 
ever 
since. 
There 
has 
been 
criticism 
of 
the 
way 
in 
which 
Wood 
et 
al. 
(1941) 
set 
up 
their 
units, 
and 
various 
authors 
have 
interpret


ed 
them 
in 
different 
ways. 
For 
example, 
the 
Uintan 
age 
was 
defined 
as 
follows: 
“Uintan 
age—new 
provincial 
time 
term, 
based 
on 
the 
Uinta 
formation 
of 
northern 
Utah, 
i.e., 
the 
time 
of 
deposition 
of 
Uinta 
A-C, 
inclusive, 
with 
the 
included 
faunas." 
Some 
authors 
have 
interpreted 
this 
strictly 
to 
mean 
that 
the 
Uintan 
age 
is 
coincidental 
with 
the 
geochronof 
the 
Uinta 
Formation. 
Other 
authors 
have 
interpreted 
it 
to 
be 
the 
time 
during 
which 
the 
animals 
lived 
that 
characterize 
the 
Uinta 
Formation. 
The 
two 
do 
not 
necessarily 
have 
equivalent 
time 
spans. 
I 
cannot 
believe 
that 
Wood 
et 
al. 
(1941) 
meant 
to 
have 
the 
first 
interpretation 
strictly 
applied 
and 
indeed 
they 
so 
state 
(p. 
6): 


"... 
the 
ages 
are 
not 
necessarily 
coextensive 
with 
their 
types, 
and 
the 
precise 
limits 
between 
successive 
ages 
are 
intended 
to 
be 
somewhat 
flexible 
and 
may 
presumably 
be 
modified 
in 
the 
light 
of 
later 
discoveries. 
Thus 
the 
Wasatchian 
age 
is 
more 
extensive 
that 
the 
known 
mammalian 
faunas 
of 
the 
type 
Wasatch 
and 
probably 
less 
extensive 
than 
the 
time 
equivalent 
of 
the 
entire 
Wasatch 
groupin 
the 
type 
area. 
The 
Barstovian 
age 
includes 
units 
which 
may 
be 
older 
than 
any 
part 
of 
the 
Barstow 
formation, 
and 
are 
certainly 
older 
than 
any 
of 
the 
faunules 
now 
known 
from 
Barstow." 


Wood 
et 
al. 
(1941) 
define 
Chadronian 
as 
"Chadronian 
age 
new 
provincial 
time 
term,

-

based 
on 
the 
Chadron 
formation, 
type 
locality 
near 
Chadron, 
Nebraska; 
type 
area, 
northwestern 
Nebraska 
and 
southwestern 
South 
Dakota; 
includes 
the 
old 
term 
"Titanotherium 
beds," 
used 
in 
its 
most 
extended 
sense. 
It 
may 
also 
be 
defined, 
faunally, 
as 
the 
time 


33 



during 
which 
Mesohippus 
and 
titanotheres 
coexisted." 
The 
basis 
for 
the 
Chadronian 
age 
is 
by 
this 
definition 
four-fold: 
(1) 
a 
geochronof 
the 
type 
locality 
(but 
see 
Schultz 
and 
Stout 
1955, 
and 
Harksen 
and 
Macdonald 
1969 
for 
two 
additional 
"type 
localities;" 


(2) 
time 
of 
accumulation 
of 
deposits 
in 
a 
type 
area; 
(3) 
the 
time 
of 
accumulation 
of 
beds 
containing 
"Titanotherium;" 
and 
(4) 
a 
biologic 
definition 
based 
on 
time 
of 
coexistence 
of 
Mesohippus 
and 
titanotheres. 
Such 
a 
definition 
does 
not 
support 
the 
interpretationthat 
the 
Chadronian 
age 
"is 
based" 
on 
the 
geochron 
of 
the 
Chadron 
Formation. 
Wood 
et 
al. 
(1941) 
also 
established 
the 
Duchesnean 
age. 
It 
was 
"based 
on 
the 
Duchesne 
River 
formation 
of 
northeast 
Utah." 
This 
was 
an 
attempt 
to 
fill 
a 
gap 
in 
the 
paleontological 
record 
that 
had 
long 
been 
recognized 
(Matthew 
1924, 
p. 
750; 
Osborn 


1929, 
p. 
99; 
Simpson 
1933, 
p. 
84). 
Wood 
et 
al. 
(1941) 
go 
on 
to 
say 
that 
"A 
faunal 
definition 
would 
be 
premature 
except 
to 
note 
the 
abundance 
of 
Te/eodus. 
Hence 
the 
faunas 
are 
listed 
separately." 
They 
then 
list 
the 
Duchesne 
River 
fauna 
and 
a 
correlative 
fauna, 
California 
Institute 
of 
Technology 
Locality 
150 
in 
the 
Sespe 
of 
California. 
In 
the 
central 
Rocky 
Mountain 
area 
two 
sections 
were 
thought 
to 
have 
sediments 
depositedduring 
a 
time 
interval 
between 
Uintan 
and 
Chadronian. 
These 
were 
at 
Beaver 
Divide, 
Wyoming 
and 
the 
Duchesne 
River 
Formation, 
Utah. 
The 
problems 
connected 
to 
the 
former 
area, 
only 
recently, 
have 
been 
cleared 
up 
in 
Emry 
(1975). 
The 
vertebrate 
fauna 
from 
the 
Duchesne 
River 
Formation 
was 
collected 
by 


0. 
A. 
Peterson, 
J. 
L. 
Kay, 
and 
John 
Clark 
of 
the 
Carnegie 
Museum 
and 
described 
during 
the 
19305. 
Scott 
(1945) 
brought 
together 
the 
various 
descriptions 
of 
the 
fauna, 
and 
added 
Came/odon 
from 
the 
Beaver 
Divide 
Uintan, 
to 
constitute 
a 
faunal 
basis 
for 
the 
Duchesnean 
age. 
The 
stratigraphy 
of 
the 
Duchesne 
River 
Formation 
has 
recently 
been 
studied 
by 
Andersen 
and 
Picard 
(1972) 
who 
also 
give 
the 
distribution 
of 
the 
vertebrate 
fossils 
within 
the 
formation. 
The 
faunal 
lists 
given 
by 
Andersen 
and 
Picard 
(1972) 
with 
the 
addition 
of 
Brachyhyops 
(Wilson 
1971b) 
are 
the 
most 
recent 
faunal 
characterization 
of 
the 
Duchesne 
River 
Formation. 


My 
reluctance 
to 
use 
the 
term 
Duchesnean 
was 
caused 
by 
the 
uncertainty 
of 
what 
constituted 
the 
faunal 
basis 
for 
Duchesnean 
age. 
In 
order 
to 
be 
useful 
for 
correlation 
beyondthe 
limits 
of 
the 
type 
area 
the 
Duchesnean 
should 
have 
a 
characteristic 
fauna. 
As 
Ted-
ford 
(1970, 
p. 
692) 
succinctly 
states, 
". 
re


.. 


vision 
of 
mammal 
'Ages' 
depends 
on 
biological 
evidences, 
as 
these 
temporal 
units 
cannot 
serve 
if 
restricted 
to 
the 
geochron 
of 
litho


... 


stratigraphic 
units." 
The 
Duchesnean 
as 
originally 
used 
by 
Wood 
et 
al. 
(1941) 
and 
Scott 


(1945) 
included 
the 
faunas 
of 
the 
Randlett, 
Halfway, 
and 
Lapoint 
members 
of 
the 
Duchesne 
River 
Formation. 
Since 
that 
time, 
as 
will 
be 
shown 
below, 
the 
Randlett 
and 
the 
Halfway 
have 
been 
placed 
in 
the 
Uintan, 
on 
faunal 
evidence, 
leaving 
only 
the 
Lapointfauna 
to 
characterize 
Duchesnean. 
Subsequently, 
Clark 
et 
ai. 
(1967) 
divided 
the 
Duchesnean 
into 
an 
early 
"La 
Pointian" 
and 
a 
later 
Viejan. 
Their 
Viejan 
is 
characterized 
bythe 
Porvenir 
l.f. 
which 
I, 
for 
reasons 
stated 
below, 
assign 
to 
the 
Chadronian, 
so 
once 
again, 
the 
Lapoint 
fauna 
is 
the 
only 
one 
left 
to 
characterize 
Duchesnean. 


A 
brief 
resume 
of 
the 
history 
since 
Scott 
(1945) 
of 
pertinent 
faunal 
elements 
used 
to 
characterize 
the 
Duchesnean 
age 
follows. 


Kay 
(1934) 
divided 
the 
Duchesne 
River 
Formation 
of 
Utah 
into 
three 
"horizons" 
which 
he 
named 
Randlett, 
Halfway, 
and 
La-
point 
from 
bottom 
to 
top. 
More 
recentlyAndersen 
and 
Picard 
(1972) 
divided 
the 
Duchesne 
River 
Formation 
into 
four 
Members,
Brennan 
Basin, 
Dry 
Gulch 
Creek, 
Lapoint,
and 
Starr 
Flat. 
The 
Brennan 
Basin 
Member 
contains 
the 
fauna 
attributed 
to 
the 
Randlett; 
the 
Dry 
Gulch 
Creek 
contains 
the 
fauna 
attributed 
to 
the 
Halfway, 
and 
the 
LapointMember 
contains 
the 
fauna 
attributed 
to 
the 
Lapoing 
horizon. 
The 
Starr 
Flat 
Member 
is 
non-fossiliferous. 


As 
faunas 
of 
either 
the 
late 
Eocene 
or 


early 
Oligocene 
in 
the 
western 
interior 
of 


North 
America 
and 
California 
became 
better 


known 
the 
tendency 
has 
been 
to 
divide 
the 


Duchesnean. 
Gazin 
as 
early 
as 
1955 
(chart 
1) 


34 



recognized 
that 
the 
fauna 
from 
the 
Randlett 
or 
Brennan 
Basin 
Member 
was 
so 
closely 
related 
to 
the 
nearby 
late 
Eocene 
Myton 
fauna 
that 
he 
included 
the 
Randlett 
within 
the 
late 
Eocene 
Uintan 
Age. 
Gazin 
(1956; 
1959) 
reaffirmed 
this 
opinion, 
which 
was 
based 
primarily 
on 
his 
study 
of 
the 
late 
Eocene 
artiodactyls.


A 
similar 
position 
was 
reached 
by 
Radinsky 
(1963) 
from 
his 
study 
of 
the 
tapiroids.
In 
regard 
to 
the 
tapiroid 
Dilophodon 
leotanus 
from 
the 
Randlett, 
he 
says: 
"Comparison 
between 
Dilophodon 
specimens 
from 
Uinta 
C, 
Randlett, 
Badwater 
and 
Sage 
Creek 
faunas 
suggest 
that 
they 
are 
all 
conspecific."

Clark 
et 
al. 
(1967), 
Wilson 
et 
al. 
(1968),

Tedford 
(1970), 
and 
Golz 
(1976) 
all 
followed 
Gazin 
(1955) 
and 
included 
the 
Randlett 
fauna 
with 
Uintan. 


The 
faunas 
of 
the 
Halfway 
or 
Dry 
Gulch 
Member 
and 
the 
Lapoint 
Member 
would 
then 
be 
left 
to 
characterize 
Duchesnean 
time. 
The 
fauna 
from 
the 
Dry 
Gulch, 
according 
to 
Andersen 
and 
Picard 
(1972), 
consists 
of 
two 
taxa. 
Eosictis 
avinoffi, 
known 
from 
a 
singlefragmentary 
C-P4, 
and 
was 
described 
by 
Scott 
(1945) 
as 
a 
felid. 
A 
single 
specimen 
as 
fragmentary 
as 
the 
type 
of 
Eosictis 
is 
not 
particularly 
useful 
for 
purposes 
of 
correlation. 
Epihippus 
intermedius 
is 
the 
other 
taxon 
that 
represents 
the 
Dry 
Gulch 
fauna 
as 
listed 
byAndersen 
and 
Picard 
(1972). 
Because 
all 
other 
species 
of 
Epihippus 
occur 
in 
the 
Uintan 
I 
would 
prefer 
to 
include 
the 
Halfway 
fauna 
as 
Uintan 
as 
did 
Simpson 
(1933; 
1946). 


Other 
authors 
list 
additional 
taxa 
from 
the 
Halfway. 
Peterson 
(1934, 
p. 
383, 
fide 
Kay) 
saysthatMesagriochoerusprimus(CM 
11904) 
"was 
taken 
from 
the 
upper 
part 
of 
the 
Halfway 
Horizon." 
Mesagriochoerus 
was 
synonymized 
with 
Protoreodon 
pumilus 
by 
Wilson 
(1971a). 
P. 
pumilus 
is 
found 
in 
both 
Uintan 
and 
Chadronian 
(Wilson 
1971a). 
Scott 
(1945) 
lists 
?Protitanotherium 
(CM 
11, 
996) 
as 
having 
come 
from 
the 
Halfway 
and 
says, 
"It 
is 
entirely 
possible 
that 
this 
fragment 
should 
be 
referable 
to 
one 
of 
the 
characteristic 
Uinta 
genera, 
Protitanotherium 
Hatcher 
or 
Diplacodon 
Marsh. 
Between 
these 
two, 
it 
is 
not 
feasible 
to 
make 
a 
definite 
choice 
because 
the 


fragment 
might 
equally 
well 
belong 
to 
either 
genus 
..." 
So 
the 
only 
useful 
taxon 
in 
the 
Halfway 
faunas 
at 
present 
for 
correlation 
purposes 
is 
Epihippus 
and 
its 
affinities 
are 
with 
the 
Uintan. 
For 
this 
reason 
I 
would 
follow 
Clark 
et 
al. 
(1967) 
and 
McKenna 
et 
al. 
(1973)
and 
include 
both 
the 
Brennan 
Basin 
(Randlett) 
and 
Dry 
Gulch 
(Halfway) 
within 
the 
Uin


tan. 


This 
left 
only 
the 
Lapoint 
fauna 
to 
characterize 
a 
Duchesnean 
time 
span. 
Clark 
et 
al. 
(1967, 
p. 
56-59) 
in 
their 
monograph 
on 
the 
Chadron 
Formation 
of 
South 
Dakota 
discuss 
their 
faunas 
in 
relationship 
to 
pre-Chadronianfaunas 
elsewhere 
including 
"the 
Vieja 
fauna." 
The 
Vieja 
fauna 
as 
used 
by 
Clark 
et 
al. 
(1967)
is 
now 
limited 
to 
the 
Porvenir 
I. 
f. 
of 
this 
report. 
Clark 
et 
al. 
(1967, 
p. 
59) 
summarize 
their 
conclusions 
as 
follows. 
I 
have 
inserted 
in 
brackets 
the 
term 
Porvenir 
l.f. 
to 
emphasizethat 
I 
regard 
the 
term 
"Vieja 
fauna" 
as 
being 
too 
inclusive. 


"The 
Chadron 
includes 
three 
distinct 
rock-
time 
units 
with 
characteristic 
faunal 
associations 
(see 
Fig. 
25). 
The 
oldest, 
the 
Ahearn, 
is 
apparently 
younger 
than 
the 
Vieja 
[Porvenir]
which 
may 
be 
regarded 
as 
late 
Duches


nean 


.... 


"The 
lower 
two 
members 
of 
the 
Duchesne 
River 
Formation, 
however, 
are 
probably 
Eocene 
and 
include 
the 
typical 
Eocene 
speciesof 
Protoreodon 
and 
Diplobunops 
but 
are 
somewhat 
younger 
than 
Uinta 
C. 
the 
upperDuchesne 
River, 
the 
La 
Point, 
includes 
the 
titanothere, 
Teieodus, 
which 
is 
associated 
with 
Mesohippus 
viejensis 
[M. 
texanus 
McGrew 
(1971)] 
and 
Agricochoerus 
[sic] 
in 
the 
Vieja 
[Porvenir 
l.f.] 
and 
with 
Mesohippusin 
the 
Cypress 
Hills. 
The 
rest 
of 
the 
known 
La 
Point 
fauna 
is 
either 
transitional 
between 
the 
Uintan 
and 
Chadron 
forms 
or 
is 
represented 
by 
specimens 
so 
inadequate 
that 
their 
relationships 
cannot 
be 
precisely 
determined. 


"The 
La 
Point 
Member 
of 
the 
Duchesne 
River 
Formation 
may 
then 
be 
properly 
considered 
typical 
of 
Duchesnean 
time 
(type 
lo


-

cality, 
12 
miles 
west 
of 
Vernal, 
Utah 
Kay,
1934) 
with 
the 
understanding 
that 
no 
rock 
section 
described 
up 
to 
the 
present 
repre


35 



sents 
all 
of 
Duchesnean 
time, 
that 
the 
LaPoint 
fauna 
is 
early 
Duchesnean, 
and 
that 
the 
ViejaFormation 
of 
Texas 
(Stoval 
[sic], 
1948) 
is 
late 
Duchesnean 
and 
should 
be 
considered 
the 
type 
for 
this 
part 
of 
Duchesnean 
time. 
Teleodus, 
associated 
with 
Poabromylus, 
Epihippusuintensis, 
and 
Diplobunops, 
indicates 
La 
Pointian 
or 
early 
Duchesnean; 
and 
the 
Teleodus-
Agriochoerus-Mesohippus 
viejensis 
[seeabove] 
association 
indicates 
Viejan 
[Porvenir] 
or 
late 
Duchesnean 
age." 


Several 
points 
in 
the 
quotation 
above 
need 
further 
comment. 
First, 
Stovall 
(1948) 
does 
not 
describe 
a 
Vieja 
Formation, 
nor 
has 
anyone 
else. 
Second, 
I 
disagree 
with 
their 
creating 
new 
"ages" 
based 
on 
the 
geochrons 
of 
lithologic 
units. 
Mesohippus 
viejensis 
as 
emphasized 
by 
McGrew 
(1941), 
is 
tied 
to 
South 
Dakota 
specimens 
and, 
as 
Tedford 
points 
out 
(1970), 
Clark 
et 
al. 
(1967) 
"are 
incorrect 
in 
characterizing 
their 
'Lapointian' 
with 
Epihippus 
and 
Diplobunops, 
neither 
of 
which 
is 
recorded 
from 
Lapoint."

Clark's 
assignment 
of 
the 
Porvenir 
l.f. 
to 
the 
Duchesnean 
was 
premature 
because 
the 
Porvenir 
l.f. 
presently 
contains 
three 
generaof 
insectivores, 
five 
genera 
each 
of 
rodents 


and 
carnivores, 
thirteen 
genera 
of 
perissodactyls, 
and 
six 
of 
artiodactyis, 
a 
total 
of 
thirty-
two 
genera 
that 
occur 
in 
common 
with 
Chadronian 
faunas 
to 
the 
north. 
For 
this 
reason 
I 
have 
assigned 
the 
Porvenir 
l.f. 
to 
the 
Chadronian. 


Tedford's 
(1970, 
fig. 
6) 
chart 
shows 
the 
occurrence 
of 
mammal 
species 
recorded 
from 
the 
Duchesne 
River 
Formation. 
More 
recent 
information 
of 
the 
occurrence 
of 
some 
of 
the 
genera, 
particularly 
those 
species 
from 
the 
La-
point, 
modified 
his 
chart. 
Most 
authors 
would 
correlate 
the 
Myton 
and 
the 
Randlett 
so 
that 
they 
would 
not 
appear 
to 
be 
as 
widely 
separated 
as 
shown 
by 
Tedford. 
Pentacemylus 
is 
now 
known 
to 
be 
present 
in 
the 
Chadron 
Formation, 
as 
is 
Poabromylus 
kayi. 
Brachyhyopsis 
present 
in 
the 
Lapoint, 
Flagstaff 
Rim, 
and 
the 
Vieja, 
as 
well 
as 
Beaver 
Divide. 
Hesso/estes, 
as 
will 
be 
reported 
later, 
extends 
down 
to 
the 
Uintan 
in 
the 
Agua 
Fria 
area 
(fide 
Gustafson). 
Dyscritochoerus 
is 
so 
fragmentary 
that, 


in 
my 
opinion, 
it 
is 
not 
identifiable. 


The 
Eocene 
artiodactyis 
of 
southern 
California 
have 
recently 
been 
studied 
by 
Golz 
(1976). 
He 
gives 
in 
his 
table 
4 
the 
North 
American 
artiodactyl 
assemblages 
of 
Duchesnean 
Age 
and 
lists 
the 
genus 
Simimeryx 
represented 
by 
S. 
hudsoni 
in 
California 
and 
S. 
minutus 
in 
the 
Lapoint, 
Utah. 
The 
closely 
re


lated 
form 
Hypertragulus 
heikeni 
was 
described 
by 
Ferrusquia-V. 
(1969) 
from 
the 
early 
Oligocene 
of 
Chihuahua 
Mexico. 
It 
is 
an 
intermediate 
between 
S. 
hudsoni 
and 
H. 
caicaratus, 
and 
very 
close 
to 
S. 
hudsoni 
and 
S. 
minutus 
and 
smaller 
than 
either. 
H. 
heikeni 
is 
associated 
with 
Protoreodon 
peterson, 
Agriochoerus 
maximus, 
cf. 
Leptomeryx, 
and 
Bathygenys 
alpha. 
The 
last 
three 
occur 
in 
Chadronian 
faunas 
in 
Montana 
and 
Wyoming.
Small 
species 
of 
hypertragulids 
extend 
from 
the 
Lapoint 
into 
the 
Chadronian. 


Protoreodon 
pumilus 
is 
also 
listed 
by 
Golz 
(1976) 
in 
the 
artiodactyl 
assemblages 
of 
Uinta 
B 
and 
early 
"Uinta 
C" 
and 
"Randlett" 
as 
well 
as 
in 
the 
Duchesnean. 
In 
addition, 
I 
(Wilson 
1971b) 
have 
found 
P. 
pumilus 
in 
the 
Chadronian 
so 
this 
taxon 
is 
not 
a 
useful 
time 
marker. 


Poabromylus 
kayi 
from 
the 
Lapoint 
fauna 
was 
compared 
by 
Wilson 
(1974) 
withPseudoprotoceras 
longinaris 
from 
the 
Chadronian 
and 
the 
two 
were 
synonymized. 
Golz 
(1976,
table 
4) 
also 
lists 
Protylopus 
pearsonensisfrom 
the 
Pearson 
Ranch 
l.f. 
of 
California 
as 
characteristic 
of 
the 
Duchesnean 
but 
the 
species 
has 
not 
been 
found 
elsewhere. 


The 
North 
American 
artiodactyl 
assemblage 
of 
Duchesnean 
age 
as 
used 
by 
Golz 
is 
not 
very 
helpful 
for 
correlation 
but 
it 
must 
be 
remembered 
that 
he, 
following 
Gazin 
(1956), 
regarded 
the 
Brennan 
Basin 
or 
Randlett 
as 
indistinguishable 
from 
the 
Uintan,
and 
his 
"North 
American 
artiodactyl 
assemblages 
of 
Duchesnean 
age" 
represent 
onlyfaunas 
considered 
by 
him 
to 
correlate 
with 


the 
Lapoint 
(Golz 
1976, 
fig. 
4).

The 
Porvenir 
l.f. 
has 
only 
four 
genera, 
Microparamys, 
Hyaenodon, 
Teleodus, 
and 
Protoreodon 
in 
common 
with 
the 
Pearson 
Ranch 


l.f. 
of 
California, 
which 
was 
placed 
in 
the 
Duchesnean 
by 
Wood 
etal. 
(1941). 
Recent 
work 
36 



by 
Coombs 
(1971) 
shows 
that 
all 
specimensof 
Simidectes 
from 
Utah 
are 
Uintan 
and 
its 
range 
to 
Duchesnean 
is 
based 
on 
its 
presence 
at 
Locality 
150 
of 
the 
Pearson 
Ranch 
l.f. 
Pterodon 
californicus 
also 
from 
the 
Pearson 
Ranch 
l.f. 
was 
made 
a 
junior 
synonym 
of 
Hyaenodon 
vetus 
by 
Mellett 
(1977). 
Unfortunately, 
the 
specimen 
of 
Hyaenodon 
from 
the 
Lapoint 
is 
only 
fragmentary 
RMT2 
ancj 
could 
only 
be 
referred 
to 
Hyaenodon, 
cf. 


H. 
vetus 
by 
Mellett 
(1977, 
p. 
20). 
Another 
specimen 
that 
Mellett 
says 
is 
of 
uncertain 
allocation 
but 
was 
tentatively 
referred 
to 
Hyaenodon, 
cf. 
H. 
vetus, 
is 
from 
the 
Chadronian 
of 
Flagstaff 
Rim, 
Wyoming. 
Wilson 
and 
Szalay 
(1976) 
report 
the 
association 
of 
Hyaenodon 
with 
Mahgarita 
stevensi, 
Protoreodon 
pumilus, 
and 
Leptoreodon 
in 
the 
“Skyline 
conglomerate" 
of 
the 
Agua 
Fria 
area. 
Gustafson 
(in 
progress) 
has 
identified 
this 
Hyaenodon 
as 
H. 
cf. 
vetus. 
With 
this 
revision, 
of 
the 
12 
taxa 
listed 
byTedford 
(1970, 
fig. 
6) 
from 
the 
Lapoint, 
only 
Simimeryx 
minutus 
is 
unique, 
five 
continue 
from 
the 
Randlett 
or 
earlier, 
and 
eight 
appear 
in 
the 
Lapoint 
and 
are 
also 
found 
in 
the 
Chadron 
Formation. 


Tedford, 
however, 
(1970, 
p. 
692) 
goes 
on 
to 
suggest 
that: 
"Teleodus, 
together 
with 
the 
first 
appearance 
in 
the 
Lapoint 
of 
Hyaenodon, 
Hyracodon, 
Poabromylus 
and 
Simimeryx, 
might 
constitute 
the 
faunal 
basis 
for 
a 
mammalian 
age 
distinct 
from 
the 
Uintan 
Both 
Scott 
(1945) 
and 
Radinsky

.. 
. 


(1967) 
question 
the 
identification 
of 
the 
specimen 
of 
Hyracodon 
primus 
and 
also 
the 
specimen 
described 
as 
Mesamynodon 
medius, 
both 
from 
the 
Lapoint; 
so 
that 
the 
first 
certain 
appearance 
of 
Hyracodon 
is 
Chadronian. 
In 
addition, 
it 
would 
be 
valuable 
to 
have 
some 
statistical 
basis 
to 
distinguish 
Teleodus 
from 
Menodus. 
At 
present, 
only 
Hyaenodon, 
Poabromylus, 
and 
Simimeryx 
have 
their 
first 
appearance 
in 
the 
Lapoint 
and 
are 
useful 
as 
the 
faunal 
basis 
for 
a 
Duchesnean 
Mammal 
Age. 


If 
the 
Candelaria 
and 
Porvenir 
l.f. 
are 
correctly 
assigned 
to 
the 
Uintan 
and 
Chadronian 
respectively, 
a 
Duchesnean 
fauna 
is 
absent 
in 
the 
Vieja 
area. 
The 
Candelaria 
l.f. 
and 
the 
Porvenir 
l.f. 
have 
only 
three 
genera 
in 
common, 
Ischyrotomus, 
Manitsha, 
and 
Protoreodon, 
whereas 
the 
Porvenir 
l.f. 
has 
six 
genera, 
Pareumys, 
Hyaenodon, 
Teleodus, 
Brachyhyops, 
Protoreodon, 
and 
Poabromylus 
in 
common 
with 
the 
Lapoint 
A 
Lapointian 
fauna 
should 
therefore 
be 
intermediate. 
If 
so, 
my 
previous 
correlation 
of 
the 
Porvenir 
and 
Lapoint 
would 
be 
in 
error. 
However, 
the 
six 
genera 
listed 
above 
that 
occur 
in 
both 
the 
Lapoint 
and 
Porvenir 
faunas 
constitute 
all 
but 
two 
of 
the 
adequately 
represented 
mammalian 
taxa 
of 
the 
Lapoint 
fauna. 


Murphy 
(1977) 
and 
Woodburne 
(1977) 
urge 
that 
one 
taxon 
be 
used 
to 
identify 
the 
lower 
boundary 
of 
a 
chronostratigraphic 
unit. 
Such 
a 
practice 
was 
suggested 
by 
Simpson(1933). 
Additional 
taxa 
help 
to 
confirm 
the 
correlation 
but 
as 
pointed 
out 
strongly 
byWoodburne 
(1977) 
and 
Murphy 
(1977), 
the 
use 
of 
more 
than 
one 
taxon 
to 
identify 
a 
chronostratigraphic 
unit 
results 
in 
diminished 
precision. 
I 
therefore 
urge 
that 
the 
first 
appearance 
of 
Mesohippus 
be 
used 
to 
mark 
the 
beginning 
of 
Chadronian 
time. 
FollowingMurphy 
(1977) 
and 
Woodburne 
(1977) 
I 
do 
not 
propose 
an 
upper 
limit 
because 
it 
would 
depend 
on 
the 
first 
appearance 
of 
another 
taxon 
for 
the 
overlying 
chronostratigraphicunit 
and 
such 
is 
beyond 
the 
scope 
of 
this 
report.

I 
urge 
Mesohippus 
for 
a 
number 
of 
reasons. 
It 
is 
widespread; 
it 
is 
common, 
and 
throughthe 
work 
of 
recent 
authors 
(Clark 
et 
al. 
1967; 
McGrew 
1971; 
Forsten 
1970, 
1971a, 
1971b) 
is 
well 
known. 
In 
contrast 
the 
titanotheres 
have 
not 
been 
restudied 
for 
almost 
50 
years.
If 
this 
practice 
is 
followed, 
the 
Porvenir 
l.f. 
is 
Chadronian 
and 
the 
first 
appearance 
of 
the 
primitive 
species 
Mesohippus 
texanus 
McGrew 
(not 
M. 
viejensis 
Clark 
and 
Beerbower) 
marks 
the 
beginning 
of 
Chadronian 
time. 


37 



SUMMARY 
AND 
CONCLUSIONS 


The 
stratigraphic 
positions 
of 
the 
Candelaria, 
Porvenir, 
Little 
Egypt, 
and 
Airstriplocal 
faunas 
are 
given 
within 
the 
Vieja 
Group.
It 
can 
be 
demonstrated 
in 
the 
field 
that, 
although 
the 
area 
is 
complexly 
faulted, 
these 
four 
local 
faunas 
occur 
in 
supt.position. 
The 
Candelaria 
l.f. 
is 
late 
Uintan 
and 
occurs 
primarily 
in 
a 
lower 
sorted 
facies 
of 
the 
Colmena 
Tuff. 
A 
K-Ar 
date 
of 
40.0 
± 
5.0 
was 
obtained 
for 
a 
volcanic 
rock 
in 
the 
underlying 
Gill 
Breccia, 
and 
38.6 
is 
believed 
to 
be 
the 
best 
date 
for 
the 
overlying 
Buckshot 
Ignimbrite.
The 
Porvenir 
l.f. 
(Viejan 
fauna 
of 
others) 
occurs 
in 
the 
lower 
part 
of 
the 
Chambers 
beneath 
an 
upper 
marker 
bed 
and 
above 
the 
Buckshot 
Ignimbrite. 
Thirty-two 
genera 
in 
the 
Porvenir 
l.f. 
occur 
in 
common 
with 
Chadronian 
faunas 
to 
the 
north 
and 
six 
are 
in 
common 
with 
the 
Lapoint 
fauna. 
The 
Little 
Egypt 
l.f. 
is 
Chadronian 
and 
is 
overlain 
bythe 
Bracks 
Rhyolite 
dated 
at 
approximately36 
m.y. 
The 
Airstrip 
l.f. 
is 
found 
in 
the 
up 


per 
part 
of 
the 
Capote 
Mountain 
Tuff, 
which 
in 
turn 
is 
overlain 
by 
the 
Mitchell 
Mesa 
Rhyolite 
(= 
Brite 
Ignimbrite) 
of 
approximately31 
m.y. 
The 
latter 
unit 
is 
widespread 
over 
the 
west 
Texas 
volcanic 
field. 
Other 
local 
faunas, 
the 
Ash 
Spring, 
an 
unnamed 
one 
in 
the 
Garren 
Group, 
and 
the 
Rancho 
Gaitan 


l.f. 
of 
Chihuahua 
Mexico 
are 
not 
in 
superposition 
but 
are 
correlated 
to 
the 
other 
local 
faunas 
on 
biologic 
criteria. 
The 
only 
basis 
for 
long 
distance 
correlation 
in 
the 
absence 
of 
K-Ar 
dates 
is 
biological. 
Unfortunately, 
the 
Duchesnean 
is 
poorlycharacterized 
biologically 
so 
that 
close 
correlation 
is 
difficult. 
The 
dates 
of 
39.3 
± 
0.8 
on 
a 
tuff 
at 
the 
contact 
of 
the 
Halfway 
and 
Lapoint 
in 
Utah 
and 
the 
date 
of 
38.6 
± 
1.2 
for 
the 
Buckshot 
Ignimbrite 
in 
Texas 
are 
close. 
Hopefully, 
a 
sufficiently 
distinctive 
fauna 
to 
warrant 
a 
mammalian 
“age" 
called 
Duchesnean 
can 
be 
found. 
I 
urge 
that 
the 
base 
of 
the 
Chadronian 
be 
marked 
by 
the 
first 
appearance 
of 
Mesohippus. 


38 



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