Browsing by Subject "Geology, Stratigraphic -- Cretaceous"

Now showing 1 - 20 of 27

A look at the hydrostratigraphic members of the Edwards Aquifer in Travis and Hays Counties, Texas
(Austin Geological Society (Texas), 1995) Hauwert, Nico M.; Hanson, John A.; Stein, Bill
A revision of Taylor nomenclature, Upper Cretaceous, Central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1965) Young, Keith, 1918-2004
Since the days of R. T. Hill (1901) two Upper Cretaceous lithic units have been used as formations but have remained unnamed. These two units have usually been called the "Lower Taylor Marl" and the "Upper Taylor Marl". If Taylor is used as a group, both of these formations belong in the Taylor Group. If one uses Hill's division system of classification, the "Upper Taylor Marl" belongs to the Taylor Division but the "Lower Taylor Marl" belongs to the Austin Division, since it is a claystone lithosome interfingering with the type Austin Chalk and is genetically part of the Austin. Schuchert (1943, p. 900) may have been aware of some of the problems and some of the confusion rising out of this nomenclatural muddle when he applied the term "unnamed formation" to the unit generally termed "Lower Taylor Marl". The "Lower Taylor" and the "Upper Taylor" are separated by the Pecan Gap Formation (Stephenson, 1918) so that the lithic sequence is claystone, chalk (or marly limestone), and claystone. In more detailed maps of the greater area of Austin, Texas, the Pecan Gap is omitted by faulting in some areas, leaving the two claystone formations in fault contact. To eliminate confusion, it is imperative that the two unnamed claystone units be named.
Comanchean stratigraphy of Kent Quadrangle, Trans-Pecos Texas
(University of Texas at Austin. Bureau of Economic Geology, 1958) Brand, John Paul
At the northern end of the Coahuila platform, the thinned Comanchean sequence consists of the newly named Sixshooter group of carbonate formations underlain by the newly named Yearwood formation. The Sixshooter group consists, in descending order, of the Buda limestone, the newly named Boracho limestone composed of the newly named San Martine and Levinson members, and the Finlay limestone at the base. Beneath the Finlay is the Cox sandstone, and beneath the Cox, the Yearwood formation, which consists of an upper limestone member previously called Rustler (Permian) and a basal conglomeratic sandstone member that rests unconformably on Permian formations. The Buda and Boracho are biostratigraphically correlative with the Washita group of central Texas; similarly, the basal part of the Levinson member and all the Finlay limestone are correlative with Fredericksburg formations. Whether any part of the Cox sandstone is contemporaneous with the Trinity group is speculative. The Yearwood is probably a Trinity, though possibly a Fredericksburg, correlative.
Cotton Valley (Upper Jurassic) and Hosston (Lower Cretaceous) depositional systems and their influence on salt tectonics in the East Texas Basin
(University of Texas at Austin. Bureau of Economic Geology, 1984) McGowen, Mary K.; Harris, David W.
Correct interpretation of the effect of basin infilling on salt mobilization is critical to understanding salt dome growth and stability. The size of salt structures in the East Texas Basin is determined by the original thickness of the underlying Louann Salt (Middle Jurassic). That is, salt structures distinctly increase in size toward the interior of the basin. Initial movement of salt apparently occurred in the marginal areas of the basin during Smackover (Late Jurassic) deposition. This movement seems to have resulted from downward creep induced by the loading of carbonate units and was enhanced by basinward tilting. During a major shift from carbonate to clastic sedimentation in the Late Jurassic, salt movement became more extensive. This salt migration was caused by uneven sediment loading of fluvial-deltaic systems in the Cotton Valley Group (Upper Jurassic) and the Hosston Formation (Lower Cretaceous). Erosion source areas on the west and north persisted throughout Cotton Valley and Hosston time. Clastics were delivered to the East Texas Basin by many small streams, rather than by one major stream, because a mature drainage system had not yet formed. The Cotton Valley Group, thought to be a fan-delta system, can be subdivided into three types of facies: prodelta deposits, delta-front deposits, and braided fluvial deposits. Fan deltas, supplied by braided streams, prograded from the north, northwest, and west. Dip-oriented sandstone trends dominate in the northwestern part of the basin and change basinward to northeast to southwest strike-oriented trends. During Hosston time, sedimentation in the northwestern part of the basin was predominantly fluvial. The depositional characteristics of sediments in this area are typical of braided streams. In the study area, parallel net-sandstone and sediment chucks are clearly defined in the distal part of the Cotton Valley but are not as well defined in the Hosston. This suggests that most deltaic sedimentation during Hosston time occurred basinward of the study area. A major transgression at the end of Hosston time resulted in the deposition of the Pettet Limestone. Apparently, the location of salt domes and salt anticlines was controlled by the position of the Smackover-Gilmer carbonate platform. This platform impeded local subsidence to the extent that fan-delta sediments of the Cotton Valley Group spread laterally across the shelf rather than stacked vertically. Sediment depocenters formed preferentially basinward of the platform, resulting in migration of the underlying salt into ridges that fronted the prograding sediment wedge. As the salt was depleted under these depocenters, subsidence slowed and thereby allowed the fan deltas to override the salt ridges. This resulted in a basinward progradation of deltaic depocenters and produced younger depocenters toward the interior of the basin. Further salt migration and differentiation of salt ridges produced the present complex array of salt domes and anticlines in the East Texas Basin. Seismic and gravity data clearly demonstrate the existence of these salt ridges and intervening sediment thicknesses.
Cretaceous carbonates of Texas & Mexico : applications to subsurface exploration
(University of Texas at Austin. Bureau of Economic Geology, 1977) Bebout, Don G.; Loucks, R. G.; Society of Economic Paleontologists and Mineralogists. Gulf Coast Section
The objectives of this symposium [were] (1) to bring together individuals from universities and industry who have conducted research on Cretaceous carbonates, in order to accelerate communication, exchange ideas, and discuss differences of opinion; (2) to emphasize subsurface carbonate studies but to include outcrop investigations which provide insight into interpreting the subsurface; (3) to cover all aspects of carbonate studies--regional geological setting, facies and depositional environments, paleontology, and diagenesis. The ... papers and abstracts include studies of regional stratigraphy, facies and depositional environments, diagenesis, geochemistry, paleontology, seismic stratigraphy, porosity, and hydrocarbon production and economics Some consider the subsurface exclusively; others, the outcropping Cretaceous; and still others describe both the outcrop and the subsurface... A majority of the papers cover Cretaceous carbonates of South and Central Texas, while a few deal with the extensive but less well known Cretaceous carbonates of West Texas. Studies of the Mexican Cretaceous are also included, with much attention given to outcropping facies that are similar to subsurface facies in Texas. Most of the papers are concerned with carbonates of Aptian, Albian, and Cenomanian age, which are widespread in the subsurface and on the outcrop of Texas and Mexico, although several cover older carbonates (Berriasian-Berremian) from the outcrop in Mexico. Two papers discuss the younger subsurface Texas carbonates of Coniacian to Campanian age.
Cretaceous of Llano Estacado of Texas
(University of Texas at Austin. Bureau of Economic Geology, 1953) Brand, John Paul
Rocks of Cretaceous age crop out along the western margins of the deeper playa basins and along the southern and southeastern margins of the Llano Estacado. The Trinity group, containing only the Paluxy sandstone; the Fredericksburg group, consisting of the Walnut, Comanche Peak, Edwards, and Kiamichi formations; and the Washita group, containing only a portion of the Duck Creek formation, have been identified in the Llano Estacado. Formations of the Trinity and Fredericksburg groups are similar lithologically and paleontologically to equivalent units in the Callahan Divide and in the northern edge of the Edwards Plateau. Zonations, applicable to northern and central Texas and Pecos County, Texas, can be extended to the isolated Cretaceous exposures in the Llano Estacado. Cretaceous strata in the Llano Estacado dip to the southeast at the rate of 7 to 8 feet per mile. Structures in the underlying Triassic and Paleozoic do not appear to be reflected in Cretaceous strata. Likewise, the locations of the isolated Cretaceous remnants do not appear to be governed by known structures in underlying units. The Comanche Peak and Edwards limestone and the Kiamichi and Duck Creek shales are chemically suitable for the manufacture of Portland cement. The Edwards limestone is a suitable road ballast material. The sand and gravel of the Paluxy formation could be utilized in concrete aggregate.
Cretaceous paleogeography: implications of endemic ammonite faunas
(University of Texas at Austin. Bureau of Economic Geology, 1972) Young, Keith, 1918-2004
Endemic ammonite faunas evolved from cosmopolitan faunas in a series of successive episodes over about 35 million years of the Cretaceous of the Gulf Coast of the United States. During basin-basin-margin tectonic adjustments the Cretaceous barrier reef was inundated or circumvented so that a cosmopolitan fauna entered the back-reef area. Gradual isolation of the fauna behind the barrier produced endemism. With the next basin adjustment the endemic fauna became extinct, and a new cosmopolitan fauna migrated into the back-reef area, likewise evolving into an endemic fauna in its turn. Six cosmopolitan-endemic cycles have been identified. Geological evidence suggests two or three additional cycles.
Depositional and diagenetic history of the Sligo and Hosston Formations (Lower Cretaceous) in South Texas
(University of Texas at Austin. Bureau of Economic Geology, 1981) Bebout, Don G.
The Sligo and Hosston Formations of Aptian age occur over thousands of square miles in the subsurface of South Texas. These two formations consist of three major coeval parts, Hosston, lower Sligo, and upper Sligo, all three of which were deposited contemporaneously to produce a time-transgressive wedge of sediment. Superimposed on the overall transgressive sequence are numerous progradational cycles composed of shoaling-upward sequences. Thirty facies were deposited in six major environments: (I) alluvial plain, (2) tidal-flat complex, (3) inner-shelf lagoon, (4) oolite-shoal complex, (5) outer-shelf lagoon, and (6) shelf margin. Shelf-margin facies include coral-caprinid wackestone, grainstone, and coralgal boundstone deposited in organic banks and associated sand shoals. Back-reef facies are dominated by oyster, toucasid, and miliolid wackestones and oncolite packstones, all deposited in low- to moderate-energy settings. The inner- and outer-shelf facies are low-energy, highly burrowed, skeletal wackestones. Oolite and skeletal grainstones deposited in mobile sand shoals and coated-grain and pellet packstones deposited in stabilized grain flats compose the oolite-shoal complex. In the Hosston tidal-flat complex, laminated sandstone, dolomite mudstone, and anhydrite were deposited on a broad sabkha. The lower Sligo tidal-flat complex, however, is characterized by abundant subtidal and intertidal deposits, including burrowed dolomite mudstone and pellet-mollusk dolomite wackestone. Supratidal facies in the lower Sligo Formation include not only laminated dolomite mudstone but also skeletal and pellet grainstones deposited as beach ridges and channel levees. Four stages of diagenesis are apparent in Sligo and Hosston rocks: submarine, early meteoric-phreatic, late meteoric-phreatic, and deep subsurface. The significance of each of these stages to the diagenetic histories of the oolite-shoal complex, inner- and outer-shelf deposits, and shelf-margin complex varies considerably, however. Except at the shelf margin, submarine diagenesis was minimal, consisting primarily of micrite rim formation, deposition of internal sediment, and grain breakage. At the shelf margin, isopachous aragonite cement was precipitated in some of the grainstone facies. Some less widespread Mg-calcite submarine cement also formed. Two ubiquitous early meteoric-phreatic events were the dissolution of aragonite allochems and the precipitation of syntaxial overgrowths on echinoderms. Excellent preservation of original oolite structure suggests that their original mineralogy was Mg-calcite and that therefore the oolites did not undergo dissolution. Rocks of the oolite-shoal complex and adjacent subtidal shelf deposits show evidence of meteoric-phreatic diagenesis, including precipitation of finely crystalline isopachous calcite, compaction and collapse of micrite rims, presence of more isopachous calcite, and mixing-zone dolomitization. Dolomitization is most pronounced in the skeletal and pelletal wackestone facies. Meteoric-phreatic diagenesis is also significant in the shelf-margin facies. An isopachous, fine-crystalline, equant calcite precipitated only where marine cements were lacking. Pore-filling fine-crystalline calcite spar is limited to skeletal molds; the dominant feature is bladed radiaxial cement. Some of this cement is the product of the inversion of aragonitic submarine cement and rudist shells; however, much appears to have been primary pore-filling cement. A coarsely crystalline, equant calcite spar was precipitated throughout the Sligo Formation as a late meteoric-phreatic product. This is the final diagenetic product in the shelf-margin facies. However, in the oolite-shoal complex and adjacent subtidal shelf deposits, dolomitization (yielding successively larger rhombs), replacement by anhydrite, cementation by pore-filling baroque dolomite, anhydrite, and euhedral calcite, and formation of authigenic quartz all occur as deep subsurface (below 610 m [2,000 ft]) diagenetic products. The diagenetic history revealed in the dolomitic tidal-flat facies resembles the diagenetic sequences documented for the oolite-shoal complex. Complete dolomitization of all units to a fine- to medium-crystalline, inclusion-rich dolomite in the tidal-flat facies is the only difference. Significant hydrocarbon production from the Sligo Formation in South Texas is restricted to three gas fields. Two reservoirs are in shelf-margin facies and the other is in shelf-platform facies. In addition, four inactive gas fields occur in the area.
Depositional systems and oil and gas plays in the Cretaceous Olmos Formation, South Texas
(University of Texas at Austin. Bureau of Economic Geology, 1986) Tyler, Noel
The Upper Cretaceous Olmos Formation in South Texas continues to be an active exploration target 60 years after oil was first discovered in this clastic assemblage. The shallow, oil-bearing formation was deposited on a broad, wave-influenced shelf. Sand accumulated in two depocenters. Initial deposition took place in a western depocenter during an early phase of wave-dominated deltaic sedimentation. Deposition of the strike-elongate delta preceded two cycles of high-constructive deltaic deposition, during which time sediments prograded seaward over the Lower Cretaceous shelf edge. These three deltaic complexes together compose the Catarina delta system. The focus of sedimentation then shifted eastward to the Big Foot delta system, where again wave-dominated deltaic sedimentation was followed by two episodes of high-constructive but wave-modified delta formation. Sands not retained in the Big Foot delta system migrated alongshore to the west, where they formed a thick retrogradational coastal/interdeltaic complex, named the Rocky Creek barrier/strandplain system. Regional uplift with concomitant erosion removed much of the updip facies tracts of the Olmos. This truncated section was then unconformably covered by Escondido shelf mudstones, thereby creating conditions favorable for stratigraphic entrapment of hydrocarbons migrating updip from the deeper basin through permeable deltaic sandstones.The resulting stratigraphic trap play is the most prolific of the seven oil and gas plays in the Olmos Formation. Six other plays produce oil and gas from a variety of structural traps, but most of the remaining oil production is from the Charlotte Fault Zone. Youthful shelf-edge gas, condensate, and oil plays are highly productive, and together with wildcat prospects further basinward offer the best potential for continued high-level production from this mature province.
Depositional systems in the Nacatoch Formation (Upper Cretaceous), northeast Texas and southwest Arkansas
(University of Texas at Austin. Bureau of Economic Geology, 1983) McGowen, Mary K.
The Nacatoch Formation of the East Texas Basin is the middle formation of the Navarro Group and consists of marine sandstones and mudstones derived largely from source areas to the northwest, north, and northeast of the East Texas Embayment. Terrigenous clastics were supplied to the Nacatoch Basin by a major northeastern dispersal system originating in southwest Arkansas. Three minor fluvial-delta systems contributed sediment in southern Red River, Delta, and Hunt Counties, Texas. Five facies are recognized in Nacatoch outcrops in southwest Arkansas: tidal-flat, tidal-channel, tidal-inlet- associated, shoreface, and shelf facies. In northeast Texas, a delta sequence occurs in south-central Hunt County, and shelf sandstones and mudstones are present in Navarro and Kaufman Counties. The lateral association of deltaic deposits and tidal-flat sequences, together with the type, scale, and distribution pattern of inferred tide-produced structures, suggests that tides within the upper microtidal to lower mesotidal range (3 to 8 ft; 1 to 2.5 m) occurred in the East Texas and North Louisiana Embayments during deposition of the Nacatoch Formation. The Nacatoch Formation in the East Texas Basin is restricted to the northern and western parts of the basin. The sandstone bodies trend mainly northeast to southwest in the northern part of the basin and north to south along the western margin. In the southern half of the basin, the Nacatoch Formation consists of mudstones. In the subsurface of the East Texas Basin, the Nacatoch Formation can generally be subdivided into nearshore and shelf deposits. Nearshore sequences include deltaic deposits in the north and the northwest parts of the basin that are located downdip from surface exposures of the same facies. Two thick net-sand axes, oriented perpendicularly to the outcrop belt, extend southward into the basin. Orientation of these sand axes changes abruptly to become parallel within the dominant northeast-southwest trend, suggesting that the delta was dominated by tides and waves. It is inferred that interdeltaic areas were sites of short barrier islands, broad tidal inlets with associated tidal deltas, and tidal flats. Offshore deposits can be arbitrarily divided into a lower and an upper sandstone sequence separated by 50 to 100 ft (16.6 to 33.3 m) of marine mudstone. Sandstone bodies of the lower sequence are elongate, exhibit gradational lower boundaries and abrupt upper contacts, and grade laterally into muddy sandstones and mudstones. Sandstones composing these depositional sequences are well sorted, calcitic, glauconitic, fine to medium grained, and contain shell fragments. The sandstone bodies are interpreted to be offshore bars, which have a geometry derived primarily from tidal currents. Sandstones of the upper sequence compose a fairly continuous sheet sand; textures and composition are similar to sandstones of the lower sequence. Tectonism, coincident with deposition, controlled local sandstone distribution patterns. Development of rim synclines concomitant with salt dome growth considerably affected the thickness and distribution of the Nacatoch Formation; for example, thick Nacatoch sections exist around Haynesville salt dome in Wood County, Texas. Other piercement domes associated with salt withdrawal basins that were active during Nacatoch deposition are Steen, Mt. Sylvan, East Tyler, Brooks, and Bethel. Few sandstones occur in the Nacatoch Formation in the southern part of the East Texas Basin. These thin, laterally discontinuous sandstone bodies do not threaten the hydrologic integrity of salt domes now being investigated to determine their feasibility for nuclear waste storage. Sandstones within the Nacatoch Formation in the East Texas Basin are important shallow oil and gas reservoirs. Hydrocarbon reservoirs from the Nacatoch Formation are restricted to the shelf-sand facies. However, hydrocarbon entrapment appears to be more a function of structural closure than of depositional facies. Hydrocarbons are produced from Nacatoch fields developed over the Van salt dome in Van Zandt County and along the Mexia-Talco fault system trend near the western margin of the basin.
Depositional systems in the Paluxy formation (Lower Cretaceous), northeast Texas-oil, gas and groundwater resources
(University of Texas at Austin. Bureau of Economic Geology, 1977) Caughey, Charles A.
The Paluxy Formation is a stratigraphic unit which is composed of sandstone and shale and extends across the northern part of the East Texas embayment. Paluxy deposits were derived from sedimentary rocks to the north, and they accumulated in shoreface and coastal plain environments associated with an irregular southward regression of the shoreline. Preserved in the sedimentary mass are three major depositional systems: a centrally located delta system, a fluvial system in the north, and a strandplain system in the west. The delta system is wave dominated, composed largely of marine-influenced sediments aligned along depositional strike. Sand isolith maxima, associated with stacked coastal barrier deposits, outline the cuspate shape of the delta system. Two principal delta lobes are recognizable; these are centered in Hunt and in Wood Counties. The fluvial system consists of a broad, sandy meanderbelt facies which thins northward into discrete channel complexes separated by floodbasin deposits. The strandplain system blankets the western embayment margin with coalescent beach ridge and associated shoreface and coastal lake deposits. Strandplain sands provide small to moderate quantities of groundwater that are generally suitable for uses other than irrigation. Fluvial system deposits furnish local areas with water for irrigation and for domestic and municipal supply. Major oil and gas accumulations occur in deltaic coastal barrier and fluvial meanderbelt facies.
Depositional systems in the Woodbine Formation (Upper Cretaceous) Northeast Texas
(University of Texas at Austin. Bureau of Economic Geology, 1971) Oliver, William B. (William Benjamin), 1944-
The Woodbine Formation is composed largely of terrigenous sediment eroded from Paleozoic sedimentary and weakly metamorphosed sedimentary rocks of the Ouachita Mountains in southern Oklahoma and Arkansas and subsequently deposited in a complex of nearshore environments along the margins of the broadly subsiding Northeast Texas Basin. Three principal depositional systems are recognized in Woodbine rocks--a fluvial system, a high-destructive delta system, and a shelf-strandplain system. Their recognition is based on a regional outcrop and subsurface investigation in which external geometry of framework sands was integrated with lithology, sedimentary structures, fossil distribution, and bounding relationships. Two components of the fluvial system, a tributary channel sand facies and a meander belt sand facies, are developed in the Dexter Member (lower Woodbine) northeast of a line from Dallas to Tyler. To the south and southwest, a high-destructive delta system is persistent throughout the entire Woodbine section. The three component facies of the delta system are: progradational channel-mouth bar sands; coastal barrier sands, deposited along shore adjacent to the channel mouth; and prodelta-shelf muds. The Lewisville (upper Woodbine) shelf/strandplain system, developed in the northern third of the basin marginal to principal deltaic facies, is composed of two facies: shelf muds and strandplain sands, accumulated along shore. Near the end of Woodbine deposition, but before transgression by Eagle Ford seas, emergence of the Sabine Uplift resulted in erosion of Woodbine sediments, which were subsequently redeposited along margins of the uplift as the Harris Sand. The close correspondence of Woodbine oil and gas fields with deltaic and strandplain sands suggests that on a regional scale facies distribution is as important as structure in governing the occurrence of hydrocarbons.
Edwards Group, surface and subsurface, central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1972) Rose, Peter R.
A thick sequence of Lower Cretaceous limestone and dolomite, known traditionally and informally as Edwards," covers much of west-central Texas and composes one of the dominant physiographic elements of the State, the Edwards Plateau. In this region the base of the Edwards is an important fresh-water aquifer. Along the inner edge of the Gulf Coastal Plain, in the Balcones fault zone, the Edwards is also exposed but severely faulted and altered by ground water. South and east of the Balcones fault zone these same rocks dip gently gulfward beneath the coastal plain. Here the Edwards is an important target for oil exploration, with nearly 400 million equivalent barrels of oil and gas located or produced to date. Stratigraphic relationships between the subsurface Edwards of this area and the Edwards of the eastern Edwards Plateau have never been securely established. The purposes of this report are (1) to delineate the stratigraphic framework of Edwards and associated rocks in the areas of the coastal plain and eastern Edwards Plateau; (2) to relate this framework with other work to the northeast and southwest; (3) to use the resulting regional framework to reconstruct a generalized paleogeography and depositional history of these rocks in Texas; and (4) to outline and explain the several diagenetic processes that have affected Edwards rocks.
Geography and geology of the Black and Grand Prairies, Texas, with detailed descriptions of the Cretaceous formations and special reference to artesian waters
(Geological Survey (U.S.), 1901) Hill, Robert Thomas, 1858-1941
Glen Rose cycles and facies, Paluxy River Valley, Somervell County, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1968) Nagle, J. Stewart (James Stewart), 1889-1952
Paleoenvironmental analysis of the alternating beds of the basal Cretaceous Glen Rose Formation in Central Texas indicates a cyclical alternation of subtidal through supratidal facies. These facies were reconstructed through detailed analysis of lithology, biota (including macrofauna, microfauna, ichnofauna, and macroflora), detrital shell dispersal, and primary sedimentary structures. Facies succession indicates that each cycle represents a subtidal to supratidal depositional regime transit; cycles are regressional, with the transgressional phase being poorly developed, if at all. This conclusion is in agreement with results of studies of the Holocene transgression, which reveal a regressional succession developed by progradation of shorelines. Some other formations show similar depositional regime transit cycles; hence the Glen Rose model may be widely applicable. Facies variations within and between cycles indicate (1) that there is no typical or ideal cycle, (2) that the cycles record successive sedimentation units within a marginal marine hypersaline lagoon or bay system, and (3) that depositional regime transit cycles have limited correlation value. Facies in the seven cycles in the lower Glen Rose, Paluxy Valley, include subtidal to supratidal flat deposits, marsh, flood plain, shoal patch reef, bay, marsh island, and shifting sand lobe deposits; the only typical aspect of the cycles is their general subtidal to supratidal succession. Mixed terrestrial, marginal marine, and marine faunas and floras within these facies tracts indicate that the lower Glen Rose in this area is a lagoonal or bay depositional system. Paucity of terrigenous elastics, abundance of evaporites, presence of serpulid-patch reefs, and relatively low diversity of faunas with an abundance of thick-shelled ostracods indicate that at least the earlier phases of the lagoonal system were hypersaline. Areal stratigraphic correlation of these depositional regime transit cycles is unwise because the cycles tend to proliferate downdip, and because units that could be used as key beds commonly are local in extent. These beds reflect similar depositional conditions which recur in homotaxial phases of different cycles; indeed potential key beds may change facies within a few miles, even when bed thickness remains nearly constant. Correlation by matching cyclesin sections less than a mile apart, however, is feasible. Several particulars are useful in recognizing position in the cycle. Burrow fillings change upwards from lime-mud to sparry calcite or dolomite--a reflection of diagenetic regime. Burrows with unlithified or partially indurated calcite mud and shells occur in subtidal sediments. Diagenetically modified burrows first appear in or above the zone of sorted and abraded shell, inferred to be the wave or beach zone. Diagenetic burrow modification is intrastratal; this plus the dense fabric with unaltered shells indicate early, soft sediment diagenesis. Paleoenvironmental evidence plus studies of the Recent support the idea that these diagenetic modifications are associated with exposure and solutional modification, dolomite by hypersalinity, sparry calcite by fresh water. Subtidal deposits contain articulated and unsorted shells, many in living position; nearshore wave zone or intertidal shells occur in beds of well-sorted and abraded detrital plates. Supratidal deposits abound in rollers or may contain abraded detrital plates in texturally inverted sediments. Supratidal marshes contain abundant remains of the plant Frenelopsis. Its tiny cells, thick epiderm, protected stomata, and poorly developed roots indicate it is a physiological xerophyte similar to Salicornia of present-day salt marshes.
Hydrogeologic significance of depositional systems and facies in Lower Cretaceous sandstones, north-central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1976) Hall, W. D. (William Douglas), 1947-
The Lower Cretaceous Hosston and Hensel Sandstones are important sources of ground water in North-Central Texas. Delineation of major depositional systems and their component facies within these formations provides a method for predicting the quantity, movement, and chemical composition of water in the aquifers. The Hosston and Hensel Sandstones were deposited during minor reversals of marine transgression onto the Texas craton by Comanchean (Lower Cretaceous) seas. A net sandstone map of the Hosston Formation shows two major depositional trends: (l) a dip-oriented (west-east) meanderbelt fluvial system, strongly influenced in the west by relief on the underlying Wichita paleoplain, which supplied sediment to (2) a strike-oriented (north-south) high-destructive, wave-dominated delta system overlying the Ouachita foldbelt in the east. The Hensel deposits prograded eastward across the relatively featureless upper surface of the Pearsall Formation, forming two depositional systems similar to those of the Hosston. The meanderbelt sandstone facies of the fluvial systems and the coastal barrier facies of the delta systems are thick, laterally persistent sandstone bodies capable of supplying greater amounts of ground water than the flood basin, lagoon-marsh- embayment, or prodelta-shelf facies, which are composed principally of mudstone and siltstone. Regional ground-water movement in both formations is to the southeast with hydraulic gradients of 10 to 15 feet per mile (2 to 3 meters/kilometers).Transmissivity averages 8,000 gallons per day per foot (1.2 liters/second/meter) in the Hosston and 5,000 gallons per day per foot (0.7 liters/second/meter) in the Hensel. Hydrochemical facies of water in the Hosston and Hensel Sandstones coincide with the principal lithogenetic facies of the two depositional systems. Ground water is dominantly of the calcium magnesium bicarbonate type in the fluvial system but changes downdip to sodium sulfate and sodium bicarbonate types in the delta systems, indicating a change in conditions of chemical equilibrium.
Limestone and dolomite resources, lower cretaceous rocks, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1966) Rodda, Peter U.
Limestone is one of the most important nonfuel mineral resources in Texas. Annual production exceeds $30 million; value added in the manufacture of such products as cement and lime amounts to about $100 million annually. Lower Cretaceous limestone is the source of more than 40 percent of the State's total production of limestone and is utilized chiefly as crushed stone (aggregate and constructional stone), sources of raw materials for lime and portland cement, chemical and industrial process stone, agricultural limestone, fluxstone, and dimension stone. Lower Cretaceous dolomite is deadbumed to refractory dolomite. Study of Lower Cretaceous limestone and dolomites (including Edwards, Comanche Peak, Goodland, Glen Rose, Devils River, and Salmon Peak Formations) from approximately 250 localities in 49 Texas counties in North Texas, Central Texas, Callahan Divide, Edwards Plateau, southeastern Balcones Escarpment, southern High Plains, and Trans-Pecos Texas, and of chemical analyses of approximately 1,000 samples delineates the occurrence, distribution, quality, reserves, and availability of these rocks as industrial raw materials. Best stone in terms of physical and chemical quality occurs in the Edwards, Devils River, and Salmon Peak Formations; the only significant deposits of Lower Cretaceous dolomite are in the Edwards Formation. Other Lower Cretaceous limestones generally are too soft for use as a quality aggregate and insufficiently pure for use as chemical grade stone. Argillaceous limestone of the Goodland and Comanche Peak Formations is suitable raw material for portland cement. Total tonnage of Lower Cretaceous limestone (Edwards and associated formations) in outcrop in Texas amounts to approximately 8 trillion tons, about 40 percent of which contains 97 percent or more calcium carbonate (high-calcium limestone). Total tonnage of Lower Cretaceous dolomite (Edwards and associated formations) in outcrop amounts to about 450 billion tons, of which about 30 percent contains at least 16 percent magnesium oxide (high-magnesium dolomite). Of the total tonnage of 8.4 trillion tons of limestone and dolomite, approximately 6 percent, or 500 billion tons, is within competitive hauling distance of existing markets. Current annual consumption of limestone in Texas amounts to about 30 million tons.
Lower Cretaceous stratigraphy, northern Coahuila, Mexico
(University of Texas at Austin. Bureau of Economic Geology, 1970) Smith, Charles Isaac, 1931-
This report presents stratigraphic data and interpretations pertaining to the origin of a continental shelf-ocean basin sedimentary complex developed during Lower Cretaceous time in northern Coahuila, Mexico. This shelf was developed within a carbonate depositional regime and provides a specific descriptive example which should be useful in the development of a comprehensive process-response model of shelf origin. Northern Coahuila, Mexico, lies below the great northern arc of the Rio Grande near the middle of the border between Texas and Mexico. It is the larger Mexican counterpart of the Big Bend area of Texas which joins it on the west. The area mapped by geologists of Petroleos Mexicanos during the course of this investigation covers about 16,000 square miles and measures at a maximum about 160 miles east-west and 120 miles north-south. Lower Cretaceous outcrops in the Serrana del Burro and southern part of the Sierra del Carmen were studied by the author.
Nomenclature revision of basal cretaceous rocks between the Colorado and Red Rivers, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1966) Fisher, W. L. (William Lawrence), 1932-
Based on need for convenient, small-scale cartographic units, the basal Cretaceous rocks in Texas from Red River to Burnet County and on the Callahan Divide are herein divided into three distinctive lithologic sequences. These are recognized by changes in facies and by the presence or absence of overlying definitive units and include: (1) North-central Texas sequence overlain by the Glen Rose Formation and characterized by siliceous conglomerates and lack of carbonate units (Twin Mountains Formation) (new name); (2) North Texas and West-central Texas sequences extending beyond pinch-out of the Glen Rose Formation with basal and stratigraphically higher clastics included in a single unit (Antlers Formation); (3) Central Texas sequence overlain by Glen Rose Formation but characterized by carbonate units and coarse, locally derived, limestone and dolomite conglomerates (Travis Peak Formation). The outcrop sequence of North-central Texas grades eastward in the subsurface to a basinal sequence overlain by the Glen Rose Formation and divided into (in ascending order) the Hosston, Sligo, Pearsall, and Hensel Formations. The name Trinity is confusing in its various uses and should be reserved for higher rank units, i.e., Group or Division, where such units are judged necessary and are clearly defined in areal scope as well as vertical sequence.
Regional stratigraphic cross sections, Comanche cretaceous (Fredericksburg-Washita division), Edwards and Stockton plateaus, West Texas : interpretation of sedimentary facies, depositional cycles, and tectonics
(University of Texas at Austin. Bureau of Economic Geology, 2000) Smith, Charles Isaac, 1931-
Six interlocking regional stratigraphic cross sections of Lower Cretaceous strata (middle Albian-lower Cenomanian) of the Edwards and Stockton Plateaus of West Texas illustrate the vertical and lateral extent of lithostratigraphic units and distribution of facies and facies tracts. Facies maps, prepared along selected horizons and thought to represent a brief period of time, and maps illustrating features along critical stratigraphic boundaries are interpreted to illustrate paleoenvironmental distributions through time, as well as stratigraphic relationships. The interval from the top of the Trinity division (cop of the Glen Rose Formation) to the top of the Comanchean Series is considered to be a natural, physically defined stratigraphic division, the Fredericksburg~Washita, containing three subdivisions that define the regional stratigraphic framework. Three and one-half depositional cycles are identified within the lower-middle subdivisions and interpreted in terms of sedimenta- tion, tectonics, and eustasy. The base of the division may be interpreted as a tectonically enhanced type-2 sequence boundary, whereas three other possible boundaries (one in the lower and two in the middle subdivision) would be considered transitional sequence boundaries if they are related to eustatic cycles.