Five supersequences have been revealed by a regional sequence stratigraphic study conducted in the Albian (109 Ma) to Recent section of the Exmouth-Barrow passive margin. The interpretation utilises a new sequence stratigraphic model developed for mixed siliciclasticcarbonate lithofacies. A high degree of resolution is brought to the study by identification of 37 regional sequence boundaries controlled by biostratigraphic, wireline and seismic data. Ditch cutting analysis, integrated into the new chronostratigraphic framework, provided detailed lithofacies maps.The five supersequences, named the Gallic, Senonian, Palaeogene, Middle Neogene and Pliocene, are based upon regional lowstand, transgressive and highstand phases. The Gallic Supersequence (late Tithonian–latest Cenomanian) represents a marine incursion of siliciclastic sediments coincident with the rifting and accelerated movement of India away from Australia. A Senonian Supersequence (latest Cenomanian–middle Maastrichtian) truncates the previous supersequence with incised canyons developed on the outer shelf. The evolution of the Senonian section corresponds to the Australian separation from Antarctica and the first appearance of carbonates.The Palaeogene Supersequence (middle Maastrichtian– late Early Miocene) dominates much of the Tertiary and is identified by a basinward shift of facies following a Maastrichtian–Paleocene sea level fall. Enhanced subsidence on the outer shelf during the Eocene created a forced transgression with carbonate mudstonesiltstone deposition. A highstand during the Oligocene– Early Miocene formed the distinctive prograding carbonate shelf recognised throughout the North West Shelf.A Middle Neogene Supersequence (late Early Miocene– Early Pliocene) is identified by an erosive base and the development of a thin lowstand fan on the outer shelf. The supersequence is largely characterised by backstepping reefs following a Middle Miocene transgression. A Late Miocene eustatic stillstand restricted reef development to the inner shelf, generating coarsegrained carbonate progrades from highstand-shedding. The final Pliocene Supersequence (Pliocene–Recent) was initiated by a eustatic fall during the Early Pliocene and was followed by the development of a transgressive, aggrading shelf.
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The Roebuck Basin is a sparsely explored, frontier province located between the Carnarvon and Browse basins on Australia's North West Shelf. Mapping of the main structural and depositional elements of the basin has led to the identification of new features and elucidated the basin's tectonic history.The newly-identified Oobagooma High is a 25 km wide north-south oriented, elongate structure that separates the Oobagooma and Rowley sub-basins at the Palaeozoic level. This structure links with the Bedout High to form a major hinge zone that stretches across the entire basin.In the study area, three sub-divisions of the Fitzroy Movement are observed which have been termed Fitzroy Movement I, II and III, of Middle Triassic, Late Triassic and Early Jurassic ages. A previously unidentified breakup event linked to Fitzroy Movement III in the Early Jurassic is inferred from the stratal geometries in the basin.The region lacks a source rock equivalent to the Upper Jurassic Dingo Claystone of the contiguous Carnarvon Basin. However, Lower Triassic marine shale and deltaic sands are well developed in the Bedout Sub-basin and based on the results of forward stratigraphic modelling using SEDPAK™ software and sequence stratigraphic correlations these sediments, have high source potential over most of the untested Rowley Sub-basin. Possible Jurassic source rocks in the Roebuck Basin were deposited under fluvio-deltaic conditions during waning thermal sag. Thinly developed sapropel zones exist in the Bedout Sub-basin but potential exists for greater thicknesses in the Rowley Sub-basin. This potential is suggested by the seismic character, sedimentary architecture and sedimentary modelling of Lower Jurassic rocks in the basin. Preliminary thermal modelling indicates that source rocks would have generated significant hydrocarbons from Middle Jurassic to the present. Timing of generation is favourable for trap formation.
An integrated biostratigraphic, wireline and seismic sequence stratigraphic study has been conducted to constrain the timing and evolution of Late Cretaceous to Tertiary depocentres along the North West Shelf of Australia. During this study a model for the sequence stratigraphic interpretation of wireline logs in this carbonate-dominated regime has been developed.A series of readily identifiable, lowstand clastic deposits interspersed within the predominantly carbonate passive margin section of the North West Shelf provide well-defined correctable events with which to divide the section. Biostratigraphic data have indicated the presence of missing section at the base of these clastic deposits and their shelfal equivalents. These events have been correlated to define sequence boundaries that are represented on wireline log data by a sharp increase in the gamma signature. Lowstand systems tracts exhibit an irregular sonic and upwardly increasing gamma signature. Transgressive systems tracts show characteristically upward-decreasing gamma and sonic profiles. Maximum flooding surfaces have been identified as the point of cleanest carbonate sedimentation represented by gamma minima on wireline logs. Log motifs exhibiting little character have been interpreted as highstand systems tracts. On seismic these sequence stratigraphic events are represented by stratal geometries that would be expected for these systems tracts.The model has enabled the definition of a higher resolution chronostratigraphic framework for the Mid Cretaceous to Recent section of the North West Shelf than has previously been possible. Forty basin-wide events have been identified from the biostratigraphic and wireline log analysis, thirty of which can be tied throughout the Barrow, Dampier and Roebuck basins.
This volume brings together 17 comprehensive, data-rich analyses to provide an updated perspective on the Mexican sector of the Gulf of Mexico, Florida and the northern Caribbean. The papers span a broad range of scales and disciplines from plate tectonic evolution to sub-basin-scale analysis. Papers are broadly categorized into three themes: (1) geological evolution of the basins of the southern Gulf of Mexico in Mexico, Bahamas and Florida and their hydrocarbon potential; (2) evolution of the region's Late Cretaceous to Neogene orogens and subsequent denudation history; and (3) geological evolution of the basins and crustal elements of the northern Caribbean. This book and its extensive datasets are essential for all academic and exploration geoscientists working in this area. The volume also includes two large maps detailing the Mexican Gulf of Mexico and the Northern Caribbean areas.
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