Cretaceous ' oceanic anoxic events' as causal factors in development of reef- reservoired giant oil fields.

Large amounts of organic C. were deposited and preserved in marine sediments of late Barremian through M. Albian and late Cenomanian-early Turonian age owing to the development of poorly oxygenated oceanic water masses and expanded oxygen minimum zones during 'oceanic anoxic events'. Sediments rich in organic C. which were deposited during such events are thick sequences of basinal black shale or mudstone, thin black beds in shelf chalks, and thin beds and lenses in rudist reef and associated limestones. We propose that the relative abundance of Mesozoic oil in the world oil picture is in part the result of maturation of organic carbon deposited during Cretaceous oceanic anoxic events. -from Authors