In the Sergipe-Alagoas Basin, along the northeast coast of Brazil, the lacustrine, middle rift sequence is composed of the Lower Cretaceous Morro do Chaves and Coqueiro Seco Formations. Subsurface analysis permitted recognition and mapping of four principal types of depositional systems that infilled the basin with more than 3,000 meters of clastic-carbonate sediments: Morro do Chaves carbonate platform, Coqueiro Seco fluvial-deltaic, Coqueiro Seco fan delta, and Coqueiro Seco slope systems. The generally poor quality of seismic profiles in this rift sequence precludes conventional seismic stratigraphic approaches. Morro do Chaves lacustrine carbonate platform sediments were deposited on shallow positive areas flanking the principal point sources (rivers), and are composed of massively bedded, high energy limestones. Contemporaneous with shallow-water sedimentation, deepwater euxinic and bituminous lacustrine shales were deposited under starved basin conditions. Sublacustrine canyon excavation attested to the presence of a destructional slope episode. Coqueiro Seco fluvial-deltaic, fan delta, and slope sediments are principally terrigenous. Fluvialdeltaic and fan delta facies display high sand/shale ratios and blocky to massive E-log patterns; slope facies display serrate to digitate E-log patterns and are less sandy. Delta plain channel-fill facies and coarse-grained meanderbelt fluvial facies are dominant in fluvial-deltaic systems, and proximal to medial conglomerates and coarse conglomeratic sandstones are dominant facies in fan delta systems. Slope facies are composed of sublacustrine fans composed of fine-to medium-grained sandstones enveloped by thick, subbituminous shales, and thin, marly, lacustrine limestones. Coqueiro Seco clastic systems prograded across the basin and buried Morro do Chaves carbonate platforms in response to tectonic pulses related to rift development. Cyclic sedimentation occurred in the highly unstable Alagoas Sub-basin where fluvial-deltaic and slope systems are dominant, but fan delta and slope systems in the less complex Rio São Francisco Sub-basin do not exhibit cyclicity. Coqueiro Seco fluvial-deltaic, fan delta and slope sedimentation terminated because of continued basin subsidence and diminishing sediment supply as source areas were leveled. Consequently, the basin became the site of lacustrine shale deposition represented by the Ponta Verde Formation in the Alagoas Sub-basin. The rift sequence is truncated by a pre-Aptian unconformity in the Rio São Francisco Sub-basin. Evaluation of petroleum occurrences in relationship to defined depositional systems permitted recognition of several types of plays characterized by unique structural and stratigraphic relationships exhibited by reservoirs, source beds and structure. The Coqueiro Seco slope play, formed by updip pinchout of turbidite fans, is judged the most promising in the sequence. / text

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Understanding the stratigraphic architecture of geologically complex reservoirs, such as the heavy oil deposits of Western Canada, is essential to achieve an efficient hydrocarbon recovery. Borehole and 3-D seismic data were integrated to define the stratigraphic architecture and generate 3-dimensional geological models of the Mannville Group in Saskatchewan. The Mannville is a stratigraphically complex unit formed of fluvial to marine deposits. Two areas in west-central and southern Saskatchewan were examined in this study. In west-central Saskatchewan, the area corresponds to a stratigraphically controlled heavy oil reservoir with production from the undifferentiated Dina-Cummings Members of the Lower Cretaceous Mannville Group. The southern area, although non-prospective for hydrocarbons, shares many similarities with time-equivalent strata in areas of heavy oil production. Seismic sequence stratigraphic principles together with log signatures permitted the subdivision of the Mannville into different packages. An initial geological model was generated integrating seismic and well-log data Multiattribute analysis and neural networks were used to generate a pseudo-lithology or gamma-ray volume. The incorporation of borehole core data to the model and the subsequent integration with the lithological prediction were crucial to capture the distribution of reservoir and non-reservoir deposits in the study area. The ability to visualize the 3-D seismic data in a variety of ways, including arbitrary lines and stratal or horizon slicing techniques helped the definition of stratigraphic features such as channels and scroll bars that affect fluid flow in hydrocarbon producing areas. Small-scale heterogeneities in the reservoir were not resolved due to the resolution of the seismic data. Although not undertaken in this study, the resulting stratigraphic framework could be used to help construct a static reservoir model. Because of the small size of the 3-D seismic surveys, horizontal slices through the data volume generally imaged only small portions of the paleogeomorphologic features thought to be present in this area. As such, it was only through the integration of datasets that the geological models were established.

Orientador: Reinaldo José Bertini / Coorientador: Paulo M. Machado Brito / Banca: Maria Rita Caetano Chang / Banca: Alexandre Magno Feitosa Sales / Resumo: 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 / Abstract: 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 / Mestre

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Sandstone units of the Upper Cretaceous San Miguel Formation in South Texas are wave-dominated deltaic sequences deposited during a major marine transgression. San Miguel sediments were deposited in the Maverick Basin within the Rio Grande Embayment. Cross sections and sandstone maps reveal that during deposition of the San Miguel Formation, the Maverick Basin consisted of two subbasins. A western subbasin received sediments from the northwest; the eastern subbasin received sediments from the north. Net-sandstone patterns show that the thickest parts of the sandstone bodies are generally strike oriented; where not eroded, updip sand-feeder systems are indicated by dip-aligned components. The San Miguel deltas vary considerably in morphology and make up a spectrum of wave-dominated delta types. Modern analogs of these San Miguel deltas include the Rhone, Nile, Sao Francisco, Brazos, Danube, Kelantan, and Grijalva deltas. Final sandstone geometries depended on three primary factors: (1) rate of sediment input, (2) wave energy, and (3) rate of sea-level change. Delta morphology was determined by all three factors, but the degree of reworking of deltaic sediments after delta abandonment was determined by wave energy and rate of transgression. The most common vertical sequences in the San Miguel coarsen upward from silt and clay to fine sand. Burrows are the dominant structures. The few primary structures are of small scale; large-scale cross beds are observed only in outcrop. Strandplain or barrier-island facies sequences, which prevail in most wave-dominated deltaic deposits, are incomplete in the San Miguel. In most places, only the lower shoreface is preserved. The upper parts of the sequences, which normally bear large-scale primary structures, were lost by marine reworking during subsequent transgressions. Intense burrowing destroyed any primary structures at the tops of the truncated sequences. Most of the San Miguel sandstones are arkoses. Cements include sparry and poikilotopic calcite, quartz overgrowths, feldspar overgrowths, illite rims, and kaolinite. The primary destroyers of porosity are the two types of calcite cement, which tend to completely cement the coarsest, best sorted, and originally most porous zones of the San Miguel vertical sequences. Zones of secondary porosity resulted from leaching of shell material, calcite cement, and feldspars. Laterally, the zones of either high secondary porosity or calcite cementation are unpredictable. / text

Geological evidence suggests large-scale continental extension during the breakup of the eastern Gondwana margin was the predominant force controlling rifting of New Caledonia from the eastern Gondwana margin and formation of the Tasman Sea in the Late Cretaceous. Tectonic models suggest slab-rollback forces elongated and thinned the crustal lithosphere detaching crustal fragments from the Gondwana margin. Current tectonic models lack detailed timing and placement of this crustal detachment with respect to New Caledonia based on lack of evidence (rocks). An isotope and paleomagnetic study was carried out on a bi-modal assemblage of volcanic rock exposed on the southwest side of New Caledonia in the Nouméa Basin. U/Pb isotope ages of zircon grains found within siliceous volcanic rock in the Nouméa Basin provide temporal evidence that volcanism persisted both before and after the breakup of the eastern Gondwana Continent (100-90 Ma) in the Late Cretaceous. Four isotope ages >97 Ma and a series (11 samples) ranging from 91-76 Ma constrain the siliceous volcanism of the Nouméa Basin to the Late Cretaceous. A paleomagnetic inquiry utilizing statistics of both McFadden/Reid and Fisher carried out on 16 Nouméa Basin siliceous and mafic in situ formations place the oldest volcanic units found within the Nouméa Basin at 650 S latitude as New Caledonia began to separate from Gondwana (~100 Ma). The data suggests a well-developed arc signature in the region, which persisted for at least 15 Ma in the Late Cretaceous. Compared to current tectonic models of the southwest Pacific Region from the Late Cretaceous to Eocene, our data suggests New Caledonia was further south on the eastern Gondwana supercontinent prior to rifting in the Late Cretaceous than current models. / Geologic background -- Tectonic setting -- Methods -- Sampling -- Results -- Discussion. / Department of Geological Sciences