Browsing by Subject "Cenozoic"
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Item Basin evolution, deformation, and magmatism during variable tectonic regimes in the region linking the central and northern Andes(2019-05) George, Sarah Winspeare Merriam; Horton, Brian K., 1970-; Baker, Paul; Ketcham, Richard; Steel , Ronald; Vallejo, CristianCordilleran style margins exhibit significant heterogeneities both along-strike and through time. These changes in tectonic regime influence sediment routing systems and topographic growth, and are often recorded in proximal basin systems. This dissertation addresses pre-Andean through Andean tectonic regimes in northern Peru and Ecuador. Although Peru has been the site of continuous subduction since at least the Jurassic, Andean shortening and associated flexure in the foreland basin system did not initiate until the latest Cretaceous. Chapter 2 explores the pre-Andean basin system and transition to Andean shortening in northern Peru. This chapter provides new maximum depositional age constraints and demonstrates protracted accumulation in extensional and post-extensional basins preceding the late Cretaceous shift to regional shortening and associated reversal of sedimentary polarity. In Ecuador, the onset of Andean shortening briefly predates the accretion of a sliver of the Caribbean Large Igneous Province in the latest Cretaceous that now comprises the bedrock to the Ecuadorian forearc. More recently, regional Neogene deformation appears to coincide with subduction of the buoyant Carnegie Ridge in the Ecuadorian trench. Chapter 3 discusses the impact of accretion and subduction of buoyant oceanic crust on the short- and long-term magmatic and deformational evolution of the Ecuadorian arc using regional detrital zircon U-Pb constraints on arc magmatism, a new reconstruction of arc location for the past 200 Ma, and a record of isotopic evolution of the magmatic arc from detrital zircons and arc rocks (εHf [subscript t] and εNd). A dramatic shift towards more evolved arc compositions at ca. 75 Ma is attributed to rapid crustal thickening. Neogene sediment dispersal systems in western Amazonia remain highly controversial, yet are significant for the birth of the Amazon River and establishment of a continuous drainage divide along western South America. Chapter 4 provides new insights into sediment routing systems in the Andes of Ecuador from Upper Cretaceous-Miocene hinterland deposits preserved between the Eastern and Western Cordilleras at 2.5 to 3 km above sea level. Using new measured sections, facies analysis, clast counts, paleocurrents, U-Pb geochronology, and palynology, this chapter demonstrates evaluates the basin infilling in the Andean basins, along with comparisons to forearc and foreland domains through timeItem Cenozoic evolution of a fragmented foreland basin, Altiplano plateau, southern Peru(2012-05) Fitch, Justin David; Horton, Brian K., 1970-Debate persists on the timing, magnitude and style of crustal shortening, uplift and basin evolution in the Andes. Many studies suggest that the central Andes, including the Altiplano plateau, were gradually uplifted as a result of protracted Cenozoic retroarc shortening. However, recent isotopic studies conclude that the Andes instead rose in pulses, with the most significant event occurring at 10-6 Ma. Many researchers attribute these rapid pulses of uplift to lower lithosphere delamination events. A better understanding of the history of Cenozoic crustal shortening is essential for determination of the mechanism(s) of Andean uplift. The well-exposed Cenozoic San Jerónimo Group was studied in the Ayaviri basin of the northern Altiplano in southern Peru. The 3-5 km-thick succession is situated at 3900-4800 m elevation, between the Western Cordillera magmatic arc and the Eastern Cordillera fold-thrust-belt. New detrital zircon U-Pb geochronological results from four sandstones and one reworked tuff in the San Jerónimo succession show large age populations indicative of syndepositional volcanism between approximately 38 and 27 Ma. A 1600-m-thick magnetostratigraphic section further constrains the depositional timing and accumulation rate of the upper portion of the succession. Sedimentological observations show a rapid transition from cross-stratified braided-fluvial sandstones to proximal channel-fill and alluvial-fan conglomerates at ~30 Ma. Paleocurrent measurements show important temporal and spatial variations in sediment dispersal patterns while conglomerate clast counts show an upsection transition from almost exclusively volcanic input to increasing contributions of clastic, quartzite, and limestone detritus. The corresponding shifts in depositional environment and sediment provenance are attributed to the activation of new thrust structures in close proximity to the basin, namely the Pucapuca-Sorapata fault system, indicating the presence of an eastward advancing fold-thrust belt dating to at least 38 Ma and reaching the Ayaviri basin within the northern Altiplano plateau at ~30 Ma.Item Cenozoic stratigraphic and tectonic history of the Grenada and Tobago basins as determined from marine seismic data, wells, and onland geology(2005) Aitken, Trevor John; Mann, Paul, 1956-This thesis presents an integrated stratigraphic and tectonic evolution of the Grenada and Tobago basins using multi-channel seismic data collected in May, 2004, (BOLIVAR cruise), along with GULFREX seismic data collected by Gulf Oil Company in 1975. These reflection data, combined with UTIG OBS refraction data also collected with the BOLIVAR study in 2004 and with a compilation of previously published, onland geologic data in the southeastern Caribbean, constrain a multi-stage, Cenozoic tectonic history for the southern Lesser Antilles arc and flanking Grenada and Tobago basins. A new tectonic model for the Grenada and Tobago basins is based on three seismic megasequences. The striking similarity in the two basins' half-graben structure, smooth basement character, deep-marine seismic facies, and similar Paleogene sediment thickness suggest that the two basins formed as a single, Paleogene forearc basin related to the now dormant Aves Ridge. This single forearc basin continued to open through flexural subsidence during the early to middle Eocene probably because of slow rollback of the subducting Atlantic slab. The Grenada and Tobago basins began to be divided during the early to middle Miocene, when the thinned crust of the forearc was inverted as a result of: 1) oblique convergence between the Caribbean plate and the passive margin of South America; and 2) intrusion of the Neogene Lesser Antilles arc. Observed transpressional shortening of the basins decreases from southwest to northeast. Total shortening in the southern Grenada basin varies from 5 km in the southern part of the study area to 1 km in the northern part of the study area. Shortening structures include inverted Paleogene normal faults, folds, and shale diapirism. The late Miocene to Recent period is characterized by divided depositional histories of the Grenada and Tobago basins. The Tobago basin is characterized by a 4-km-thick wedge of Plio-Pleistocene clastic sediments inferred to represent the distal progradation of the proto-Orinoco River. The Grenada basin becomes increasingly isolated from further continental sediment input by uplift of coastal Venezuelan ranges and the Neogene Lesser Antilles volcanic ridgeItem Chronology of Cenozoic tectonic events in western Venezuela and the Dutch Antilles Islands based on integration of offshore seismic reflection data and onland geology(2005) Gorney, David Luke; Mann, Paul, 1956-Newly acquired BOLIVAR seismic reflection data from offshore western Venezuela and the Dutch Antilles are combined with existing geologic and geophysical data sets to examine the complex chronology of tectonic events affecting the onshore Falcon basin and the adjacent offshore basins. This study also describes the seismic acquisition, processing, and interpretation methods applied to the BOLIVAR seismic reflection data and used in this study. Three tectonic phases are constrained using these data: 1) Paleogene back-arc opening of the 3 to 6 km thick Falcon-Bonaire basin is the initial tectonic phase that occurred along east-west striking normal fault systems that have locally been inverted by later tectonic phases. These normal faults control the oldest depositional sequences and parallel the trend of the Bonaire basin. 2) northwest-striking normal faults crosscut these older normal faults and form deep submarine rifts that contain up to 4 km of sedimentary fill, forming deep water channels between the Dutch Antilles islands. Offshore well data and the age of onshore sediments in the Falcon basin indicate that this second phase rifting occurred in the late Oligocene through the early Miocene. 3) inversion of the Falcon basin commenced during the middle Miocene; this inversion phase is reflected in the present-day pattern of east-northeast-trending fold belt that can be traced over 200 km in the Falcon basin; a second fold-thrust belt (La Vela) can be traced over a distance of 175 km parallel to the Falcon coast; restoration of imbricate thrusts seen on seismic lines perpendicular to the Falcon coast indicates a minimum of 7 km of northeast-southwest directed thin-skinned shorteningItem Fluvial and Eolian Depositional Systems, Paleosols, and Paleoclimate: Late Cenozoic Ogallala and BlackWater Draw Formations, Southern High Plains, Texas and New Mexico(1995) Gustavson, Thomas C.The late Tertiary Ogallala Formation contains the Ogallala (High Plains) aquifer, which is the major source for water for agricultural and domestic use on the Southern High Plains of Texas and New Mexico and the overlying perched aquifers. This study, which is based on outcrop and subsurface data including both log and core information, was undertaken to provide regional geologic information necessary to evaluate and provide information for the Department of Energy's (DOE's) efforts to remediate contamination of the vadose zone and of the perched aquifer above the Ogallala aquifer at the DOE's Pantex Plant in eastern Carson County. Deposition of the basal fluvial sediments of the Ogallala Formation in northwestern Texas and eastern New Mexico was controlled by topography on the underlying erosional surface. Paleovalley-fill facies consist of heterogeneous gravelly and sandy ephemeral-stream deposits and sandy to clayey overbank deposits interbedded with and overlain by eolian sediments deposited as sand sheets and loess. Uplands on the pre-Ogallala erosional surface are overlain by similar eolian sediments. Buried calcic soils consisting mostly of CaCO3 nodules and filaments occur throughout the eolian facies.Item Late Cenozoic deposits of the Texas Coastal Plain between the Brazos River and the Rio Grande(1941) Weeks, Albert William, 1901-; Cuyler, Robert HamiltonItem Late Cenozoic Faults of the Region Surrounding the Eagle Flat Study Area, Northwestern Trans-Pecos Texas(1993) Collins, Edward W.; Raney, J. A.The Eagle Flat study area is located along the southeastern edge of the southern Basin and Range-Rio Grande tectonic province in Trans-Pecos Texas. The desert region that encompasses the study area consists of the broad Diablo Plateau and a series of mountain ranges and adjacent intermontane basins that formed by extensional faulting that probably occurred in the last 24 mya. There has been no historical surface rupturing of faults in Trans-Pecos Texas, although earthquakes have occurred and faults that displace Quaternary (present to approximately 2 mya) deposits are present (fig. 1). Geologic investigations of faults active during the Quaternary provide important data (tables A-1 and A-2) for seismic risk studies of the proposed Eagle Flat low-level radioactive waste repository. Most of the Quaternary faults of Trans-Pecos Texas are between about 11 and 24.8 mi (18 and 40 km) long (table A-1). Many of the faults are sections of longer fault zones that are between 43 and 64 mi (70 and 105 km) long. Strikes of individual faults are variable, although most of the fault zones strike northwestward or northward. Faults dip between 50° and 89°. Fourteen Quaternary faults are within 31 mi (50 km) of the proposed repository.Item Late Cenozoic Geomorphic Evolution of the Texas Panhandle and Northeastern New Mexico: Case Studies of Structural Controls of Regional Drainage Development(1984) Gustavson, Thomas C.; Finley, Robert J.Salt dissolution has affected parts of the Upper Permian Salado, Seven Rivers, San Andres, Glorieta, and upper Clear Fork Formations beneath the Pecos River Valley in eastern New Mexico and beneath the Canadian River Valley and the Rolling Plains of the Texas Panhandle. Extensive dissolution of the salts of the Salado and Seven Rivers Formations has also occurred beneath the Southern High Plains. The cumulative thickness of salt lost to dissolution exceeds 150 m (500 ft) along the western, northern, and eastern margins of the Palo Duro Basin. Dissolution and subsidence occurred during the deposition of the Tertiary Ogallala Formation, but Ogallala deposition kept pace with subsidence. Following the end of Ogallala deposition in the late Pliocene, surface subsidence resulted in lacustrine basins along trends of relatively rapid dissolution. Preserved lacustrine sediments contain Blancan faunas, confirming minimum late Pliocene ages for the basins. Continued subsidence along trends of relatively rapid dissolution during the late Tertiary and early Quaternary resulted in a series of basins that diverted many of the streams flowing southeasterly across the Southern High Plains. As a result of subsidence, the headwaters of the ancestral Brazos River were diverted during the middle Pleistocene from a southeasterly drainage through the Portales paleovalley to a southerly drainage through the Pecos Valley. The present-day headwaters of the Canadian River are probably a former tributary of the Pecos-Portales-Brazos system that was diverted to the northeast along a subsidence trend caused by dissolution during the late Pliocene or early Quaternary.Item Letter to A.S. Warthin, Jr. from H.B. Stenzel on 1942-10-28(1942-10-28) Stenzel, Henryk B.Item Letter to C.Wythe Cooke from H.B. Stenzel on 1942-03-09(1942-03-09) Stenzel, Henryk B.Item Letter to Ellen James Moore from H.B. Stenzel on 1962-10-25(1962-10-25) Stenzel, H.B.Item Letter to Emily H. Vokes from H.B. Stenzel on 1969-01-09(1969-01-09) Stenzel, Henryk B.Item Letter to Fedrico Bonet from H.B. Stenzel on 1968-04-25(1968-04-25) Stenzel, Henryk B.Item Letter to H.B. Stenzel from A.S. Warthin, Jr. on 1942-10-15(1942-10-15) Warthin, A.S., Jr.Item Letter to H.B. Stenzel from Borivoj Zaruba on 1965-10-22(1965-10-22) Zaruba, BorivojItem Letter to H.B. Stenzel from C.Wythe Cooke on 1942-02-24(1942-02-24) Cooke, C.WytheItem Letter to H.B. Stenzel from Darcy Closs on 1964-05-30(1964-05-30) Closs, DarcyItem Letter to H.B. Stenzel from Harry S. Ladd on 1951-03-08(1951-03-08) Ladd, Harry S.Item Letter to H.B. Stenzel from Harry S. Ladd on 1951-11-16(1951-11-16) Ladd, Harry S.Item Letter to H.B. Stenzel from J.B. Garrett on 1948-01-13(1948-01-13) Garrett, J.B.