Neoproterozoic deglacial sediments and their hydrocarbon source rock potential
Published:January 01, 2012
Daniel Paul Le Heron, Jonathan Craig, 2012. "Neoproterozoic deglacial sediments and their hydrocarbon source rock potential", Glaciogenic Reservoirs and Hydrocarbon Systems, M. Huuse, J. Redfern, D. P. Le Heron, R. J. Dixon, A. Moscariello, J. Craig
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Many Neoproterozoic successions contain viable hydrocarbon source rocks, even though they were deposited before most extant life forms evolved. Eukaryotic microalgae, bacteria, chlorophyte micoalgae, marine pelagophyte algae and dinoflagellates may have contributed organic matter. Major global-scale glaciations, which are commonly attributed to a ‘snowball’ or ‘slushball’ Earth scenario, or deposited under a ‘zipper rift’ scenario, are believed to have played an important role in the deposition of hydrocarbon source rocks during the mid- Neoproterozoic (Cryogenian). Phases of Cryogenian deglaciation may have culminated in the deposition of high total organic carbon shales and ‘cap carbonates’ in restricted anoxic basins, which may have been carved by ice sheets themselves or, alternatively, formed as restricted extensional half graben as Rodinia began to fragment. One example of these organically enriched deglacial sediments comprises shales and dolostones deposited following the Sturtian glaciation in the Centralian Superbasin of Australia, an amalgam of basins that extends almost continent-wide across Australia. Data from the Marmot MMDD-1 drill core on the Stuart Shelf in the southern part of the Centralian Superbasin, together with previously published data on organic enrichment in the Amadeus Basin in the central part of the Centralian Superbasin, suggest that the deposition of organically enriched shales was widespread during the Sturtian deglaciation.
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Glaciogenic Reservoirs and Hydrocarbon Systems
Glaciogenic reservoirs and hydrocarbon systems occur intermittently throughout the stratigraphic record, with particular prominence in Neoproterozoic, Late Ordovician, Permo-Carboniferous and Late Cenozoic strata. Recent interest in glaciogenic successions has been fuelled by hydrocarbon discoveries in ancient glaciogenic reservoirs in North Africa, the Middle East, Australia and South America. Glaciogenic deposits of Pleistocene age are noteworthy for their content of groundwater onshore and potentially prospective and/or hazardous gas accumulations offshore. The abundant imprints of Pleistocene glaciations in both hemispheres can be used to reconstruct complex histories of repeated ice cover and retreat, and glacier-bed interactions, thus informing our view on the dynamics of older ice caps and predictions of future glaciations. This volume aims to provide a better understanding of glaciogenic processes, their stratigraphic record and reservoir characteristics of glaciogenic deposits. The book comprises 3 overview papers and 16 original case studies of Neoproterozoic to Pleistocene successions on 6 continents and will be of interest to sedimentologists, glaciologists, geophysicists, hydrologists and petroleum geologists alike.