Carbonate platforms contain a wealth of information regarding the changing biota, sea level, ocean-chemistry, and climate of the Cretaceous Period. The Comanche platform of the northern Gulf of Mexico represents a vast, long-lived carbonate system that extended from west Texas through the Florida panhandle. In central and south Texas, excellent outcrops and an extensive suite of subsurface data provide an opportunity to document the evolution of this system, from the shoreline to the shelf-margin and slope. This study examines the changing facies, platform morphologies, and shelf-margin architectures of the mixed carbonate-siliciclastic, middle-Hauterivian to lower-Campanian interval. Stratigraphic results are integrated with stable-isotope geochemistry to document the detrimental effects of oceanic anoxic events on the carbonate platform. Seven second-order, transgressive-regressive supersequences of 3-14 Myr duration are defined in south Texas using sequence stratigraphic analysis of shelf-interior facies successions. Second-order supersequences are subdivided into several third-order depositional sequences of 1-3 Myr duration. In these sequences, facies proportions and stratal geometries of the shelf-interior are found to be the result of changing platform morphology and temporal evolution from distally-steepened ramp to rimmed-shelf depositional profiles. Shelf-margin trajectories, stratigraphic architectures, and facies proportions are a function of long-term accommodation trends expressed in second-order supersequences. These characteristics are modified by lateral variability in the underlying structural/tectonic setting and localized syndepositional faulting. The stratigraphic equivalents of oceanic anoxic events 1a, 1b, 1d, 2, and 3 are documented in the Cretaceous section of south Texas. These oceanic anoxic events coincided with maximum flooding zones of supersequences and are linked to carbonate platform drowning events on four separate occasions. The occurrence of oceanic anoxic events is found to be a fundamental driver of carbonate platform morphology, faunal composition, and facies evolution in transgressive-regressive supersequences of the northern Gulf of Mexico. / text

For decades the Upper Cretaceous Lower Tuscaloosa Formation of the U.S. Gulf Coast has been considered an onshore hydrocarbon play with no equivalent offshore deposits. A better understanding of the Lower Tuscaloosa sequence stratigraphic and paleogeographic framework, source-to-sink depositional environments, magnitude of fluvial systems, regional trends in reservoir quality, and structural influences on its deposition along with newly acquired data from offshore wells has changed this decades-long paradigm of the Lower Tuscaloosa as simply an onshore play. The mid-Cenomanian unconformity, underlying the Lower Tuscaloosa, formed an extensive regional network of incised valleys. This incision and accompanying low accommodation allowed for sediment bypass and deposition of over 330 m thick gravity-driven sand-rich deposits over 400 km from their equivalent shelf edge. Subsequently a transgressive systems tract comprised of four fluvial sequences in the Lower Tuscaloosa Massive sand and an overlying estuarine sequence (Stringer sand) filled the incised valleys. Both wave- and tide-dominated deltaic facies of the Lower Tuscaloosa are located at the mouths of incised valleys proximal to the shelf edge. Deltaic and estuarine depositional environments were interpreted from impoverished trace fossil suites of the Cruziana Ichnofacies and detailed sedimentological observations. The location and trend of valleys are controlled by basement structures. Lower Tuscaloosa rivers were 3.8m – 7.8m deep and 145m – 721m wide comparable to the Siwalik Group outcrop and the modern Missouri River. These systems were capable of transporting large amounts of sediment indicating the Lower Tuscaloosa was capable of transporting large amounts of sediments to the shelf edge for resedimentation into the deep offshore. Anomalously high porosity (>25%) and permeability (>1200md) in the Lower Tuscaloosa at stratigraphic depths below 20,000 ft. are influenced by chlorite coating the detrital grains. Chlorite coatings block quartz nucleation sites inhibiting quartz cementation. Chlorite coats in the Lower Tuscaloosa are controlled by the presence and abundance of volcanic rock fragments supplying the ions needed for the formation of chlorite. Chlorite decrease to the east in sediments derived from the Appalachian Mountains. An increase in chlorite in westward samples correlates with an increase of volcanic rock fragments derived from the Ouachita Mountains. / text

Made available in DSpace on 2014-06-11T19:26:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-05-05Bitstream added on 2014-06-13T19:13:16Z : No. of bitstreams: 1 voltani_cg_me_rcla.pdf: 3761766 bytes, checksum: b819d81d58be398c33a3c1bcd92c037f (MD5) / A Bacia do Araripe é a maior estrutura bacinal interior do Nordeste brasileiro, com História Geológica apresentando registros desde a Era Paleozóica. Mas é do Cretáceo que vem sua notabilidade. O Membro Romualdo da Formação Santana é um autêntico lagerstätten, cujos fósseis estão magnificamente preservados e são muito diversos, especialmente entre os vertebrados. Entre estes estão descritos cerca de 30 morfótipos de peixes. Uma parte significativa desta diversidade encontra-se depositada no Museu de Paleontologia e Estratigrafia “Paulo Milton Barbosa Landim”, UNESP, Campus de Rio Claro. São 13 gêneros representados, distribuídos em 3.119 espécimens. Parte deste material foi analisado, a fim de trazer contribuições sobre a Osteologia de cada grupo, bem como Paleobiogeografia, Paleoecologia, Cronobioestratigrafia / The Araripe Basin is the largest interior basin structure from Northeastern Brazil, which has a Geological History presenting data since the Paleozoic Era. Nevertheless its notability comes from the Cretaceous. The Romualdo Member from the Santana Formation is an authentic largerstätten, containing an excellently preserved diverse fossil assemblage, especially vertebrates. Among those are described about 30 morphotypes of fishes. A meaningful portion of this diversity is found deposited on “Museu de Paleontologia e Estratigrafia “Paulo Milton Barbosa Landim”, UNESP, Rio Claro Campus. There are 13 genera represented, distributed on 3.119 specimens. Part of this material has been analised, in order to contribute with the Osteology of each group, as well as to Paleobiogeography, Paleoecology and Chronobiostratigraphy

Made available in DSpace on 2015-02-24T19:48:44Z (GMT). No. of bitstreams: 1 SilvanaPPG_TESE_pag119_final.pdf: 4384081 bytes, checksum: f4e3889e03bd2b77ef4e8f1b271723a8 (MD5) Previous issue date: 2012-08-06 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The Northeast relief was described by the Pediplanation Model. This action discards the theoretical basis of post-Cretaceous tectonic evolution of the landscape. Through this model the Massif Pereiro - MP, Borborema Province, was established as part of the Tablelands Area Residual Sertanejos. The present work aims to establish the post- Cretaceous morphotectonic evolution of the MP by geomorphological and geological mapping using Geographic Information System, Remote Sensing and dating of sediments by Single Aliquot Regenerative-dose (SAR). The MP is contained in the core semi-arid, annual precipitation of 600-800 mm / year. The MP is NE-SW, is limited by Shear Zone Jaguaribe (ZCJ) and Portalegre Shear Zone (ZCPa), the same attitude, and crossed by several other shear zones. These shear zones show evidence of brittle Cenozoic reactivation, mostly as normal faults and shallow crustal level. The Quaternary sedimentation around the MP focuses on fault escarpments in a general pattern cascade, where ages decrease from the summits of the steep foothills. The ages of 51 sediment samples indicate a correlation with global climate following pulses: Last Interestadial-UI, the Last Glacial Maximum - LGM and the transition Pleistocene / Holocene, while the latter focus on 18 of 51 samples dated. This study also finds evidence of a new quaternary basin, here called Merejo Basin. Through these results it is concluded that no evidence of post-Cretaceous tectonic evolution of morphological MP, as their retreat along the fault scarps, invariably following the trend of the shear zones. The erosion of cliffs in large time scale is controlled by weakness zones generated by faults on the other hand the erosion of cliffs in short time, with the formation of deposits and colluvial horizons pedogenizados, has climate control. It was also found that in the study area there is a preponderance of past and current tectonic erosion processes on the morphological evolution / O relevo do Nordeste foi descrito por meio do modelo de pediplana??o. Esta base te?rica descarta a atua??o da tect?nica p?s-cret?cea na evolu??o da paisagem. Atrav?s deste modelo o Maci?o do Pereiro MP, Prov?ncia Borborema, foi definido como parte do Dom?nio dos Planaltos Residuais Sertanejos. O presente trabalho tem por objetivo estabelecer a evolu??o morfotect?nica p?s-cret?cea do MP, atrav?s da cartografia geol?gica e geomorfol?gica com uso de Sistema de Informa??o Geogr?fica, Sensoriamento Remoto e data??o de sedimentos por Single Aliquot Regenerative-dose (SAR). O MP est? contido no n?cleo semi?rido, de precipita??o anual entre 600 a 800 mm/ano. O MP tem dire??o NE-SW, ? limitado pela Zona de Cisalhamento de Jaguaribe (ZCJ) e Zona de Cisalhamento Portalegre (ZCPa), de mesma atitude, e atravessado por v?rias outras zonas de cisalhamento. Estas zonas de cisalhamento apresentam evid?ncias de reativa??o fr?gil cenozoica, na sua maioria como falhas normais e de n?vel crustal raso. A sedimenta??o quatern?ria em torno do MP se concentra em escarpas de falhas, em um padr?o geral em cascata, onde as idades diminuem das cimeiras aos sop?s das escarpas. As idades de 51 amostras de sedimentos indicam correla??o com seguintes pulsos clim?ticos globais: ?ltimo Interestadial- UI, o ?ltimo M?ximo Glacial - UMG e a transi??o Pleistoceno/Holoceno, sendo que nesta ?ltima concentram-se 18 das 51 amostras datadas. O presente trabalho tamb?m encontra evid?ncias de uma nova bacia quatern?ria, aqui denominada de Bacia Merejo. Atrav?s destes resultados conclui-se que h? evidencia de tect?nica p?s-cret?cea na evolu??o morfol?gica do MP, pois as suas escarpas recuam paralelamente ?s falhas, seguindo invariavelmente o trend das zonas de cisalhamento. A eros?o das escarpas em grande escala de tempo ? controlada pelas zonas de fraqueza geradas pelos falhamentos, por outro lado ? eros?o das escarpas em curtos espa?os de tempos, com a forma??o dos dep?sitos coluvionares e horizontes pedogenizados, possui controle clim?tico. Concluise ainda que na ?rea de estudo haja a preponder?ncia da tect?nica pret?rita e atual sobre os processos erosivos na evolu??o morfol?gica

The Klikov Formation (Upper Cretaceous) represents the lowest stratigraphic unit of the South Bohemian basins. It provides record of continental deposits related to fluvial processes. Analysis of facies and architectures supplemented with paleocurrents data provided a basis for interpretation of depositional system exposed underground on the locality Hosín-Orty. In this study identifies sedimentary facies corresponding to high-energy river environmnent with dominance of traction current deposition are identified. Next to this, facies corresponding to low-energy deposition from suspension is preserved. From the perspective of architecture analysis depositional record represent active river channels and their fills eventuelly fills of abandoned channels. Low dispersion of paleocurrent values is consistent with a low-sinuosity river. Vertical aggradation of channels, dominance of river bars in channel-fill, downstream accretion, absence of ripples, point-bars, lateraly accreted patterns and floodplain deposits correspond with braided river environment. Stratigraphic units A, B, C, D, E, F corresponding to fluvial environment or environment of abandoned channel were distinguished. The direction of river flow is interpreted to northeast in unit A, and northwest in unit B, respectively. Autogenic and...

This thesis deals with systematic revision, evolutionary trends, palaeoecology and migration patterns of crustaceans (Cirripedia and Decapoda) from the Upper Cretaceous of the Bohemian Cretaceous Basin. Thesis is presented as a compilation of 9 papers that were published in scientific peer-reviewed journals and includes not only old museum material, but also numerous crustacean specimens which have been recovered in the last decade. Besides, short remarks on fossil crustaceans currently under study or in the process of being published (Paraclythia, Oncopareia, Acrothoracica) are also included in this thesis. In view of the fact that the fossil crustaceans from the BCB were most recently recorded in the turn of the 19th and the 20th centuries (and partially revised in the first half of the 20th century) and since the systematics and taxonomy have changed significantly, all papers presented here focus primarily on systematic revision and modern description. The essential part of the thesis thus deals with taphonomy and its bearing on the identification of fossil material. Thanks to a modern description, new species of Ctenocheles fritschi (axiidean shrimp), Archaeochionelasmus nekvasilovae (acorn barnacle), Myolepas reussi and Capitulum sklenari (pedunculate barnacles) were erected. C. fritschi is...

No description available.

The Trail Member of the upper Cretaceous Ericson Sandstone, part of the Mesaverde Group, is exposed along hundreds of square kilometers through Wyoming along the flanks of several Laramide structural uplifts. This presents a unique opportunity to study the detailed architecture based on bed-scale heterogeneity and better assess the reservoir potential of these strata in outcrop exposure on a regional-scale, and to then relate these observations to producing fields nearby. The fluvial-dominated Trail Member formed as sediments traveled from the active Sevier thrust belt to the Cretaceous Interior Seaway, forming a basinward progradational clastic wedge along a relatively high gradient. The high energy, tectonically active setting led to preservation of sand-rich, often compositionally immature fluvial strata. Though there is an abundance of sand-rich strata in the Trail Member, production from this interval has been unpredictable in current and past fields such as the Trail Unit of southwestern Wyoming.Twelve detailed stratigraphic columns were described at three sites along the eastern flank of the Rock Springs Uplift to show facies heterogeneity beyond what is often available through wells, 69 hand samples were collected for determination of porosity and permeability, and photogrammetric characterization was performed at the three sites. Average porosity decreases along strike from north to south along with net-to-gross. The vertical changes in fluvial architecture within the Trail Member reflect changes in available accommodation. While thickness of the Trail Member is highly variable, ranging between 79 to 108 meters across the study area, there is an overall trend of thickening to the south. Although the character of the Trail strata changes appreciably along strike direction, this interval is consistently rich in sand, and grain size does not change drastically along the length of observed outcrops. This study demonstrated that spatial variability in the thickness, local accommodation, porosity, and net-to-gross of the Trail Member, as well as temporal variability in the amount and character of reservoir sands and channel stacking patterns play an important role in the unpredictability of this reservoir. This study will enable reservoir modeling and aid in future exploration projects within the Trail Member and other comparable systems with similar fluvial architecture and internal heterogeneity.

No description available.

Use of Re-Os systematics in sulfides from the Bagdad porphyry Cu-Mo deposit provide information on the timing of mineralization and the source of the ore -forming elements. Analyzed samples of pyrite, chalcopyrite and molybdenite mainly from the quartz monzonite and porphyritic quartz monzonite units are characterized by a moderate to strong potassic alteration (secondary biotite and K- feldspar). Rhenium concentrations in molybdenite are between 330 and 730 ppm. Two molybdenite samples from the quartz monzonite and porphyritic quartz monzonite provide a Re-Os isotope age of 71.7 ± 0.3 Ma. A third sample from a molybdenite vein in Precambrian rocks yields an age of 75.8 ± 0.4 Ma. These molybdenite ages support previous suggestions of two mineralization episodes in the Bagdad deposit. An early event at 76 Ma and a later episode at 72 Ma. Pyrite Os and Re concentrations range between 0.008-0.016 and 3.9-6.8 ppb, respectively. Chalcopyrite contains a wide range of Os (6 to 91 ppt) and Re (1.7 to 69 ppb) concentrations and variable ¹⁸⁷Os/¹⁸⁸Os ratios that range between 0.13 to 22.27. This variability in the chalcopyrite data may be attributed to different copper sources, one of them the Proterozoic volcanic massive sulfides in the district, or to alteration and remobilization of Re and Os. Analyses from two pyrite samples yield an eight point isochron with an age of 77 ± 15 Ma and an initial ¹⁸⁷Os/¹⁸⁸Os ratio of 2.12. This pyrite Re-Os isochron age is in good agreement with the molybdenite ages. We interpret the highly radiogenic initial 1870s/188Os as an indication that the source of Os and, by inference, the ore-forming elements for the Bagdad deposit, was mainly the crust. This conclusion agrees with previous Pb and Nd isotope studies and supports the notion that a significant part of the metals and magmas have a crustal source.