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Title: Geochemical consequences of Cretaceous sea level rise
Author: Bata, Timothy Peter
ISNI:       0000 0004 5914 6610
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2016
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During the Cretaceous, the CO2 content of the global atmosphere increased in response to the volcanism associated with the disintegration of the former continents. This led to a considerable rise in global temperatures, leading to a significant rise in the global sea level and the landward movement of coastlines. Cretaceous marine strata transgressed directly on the underlying basement or much older sedimentary strata. Extreme environmental conditions in the Cretaceous involved a possibly more acidic and chemically destructive atmosphere than at present, which favoured widespread deep weathering at that time. The extensive Cretaceous palaeo-seaways played a vital role in transporting and depositing the huge volume of sediments generated during the weathering events, which included economically important placer deposits (e.g., gold, diamond and platinum). A direct consequence of the extreme Cretaceous global warmth was the widespread development of Cretaceous silcretes. Much of the world's heavy oil occurs in Cretaceous reservoir sands. The geological processes responsible for the widespread occurrence of the Cretaceous oil sands can also be traced back to the unique Cretaceous greenhouse climatic condition. The warm climatic conditions imply a higher heat flow regime in the subsurface, which contributed to the thermal maturation of the organic rich sediments that are closely associated with the Cretaceous transgressive sands. The oils were generated as conventional light oil, which later degraded into heavy oils, rather than thermally cracked oils from over-matured source rocks. Oils migrated into shallow warm reservoir sands that were favourable for microbial activities. All the studied Cretaceous oil sands show evidence of hopane degradation without the formation of 25-norhopanes despite diasterane degradation in some of the samples. This strongly implies that biodegradation in these studied Cretaceous oil sands occurred at shallow depths. Pyrite precipitated from an open system by means of microbial sulfate reduction as part of the biodegradation process.
Supervisor: Not available Sponsor: Petroleum Technology Development Fund of Nigeria (PTDF)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Sea level ; Oil sands ; Geology ; Stratigraphic