Evolution of the Biosphere
We know of the occurrence of petroleum and petroleum precursors (kerogen and bitumen) in Precambrian time (Nonesuch Shale, Michigan, USA). Through the Cambrian and up to the Devonian, mainly marine phytoplankton and bacteria, and to some extent benthonic algae and Zooplankton could have served as source material for petroleum. Thereafter, terrestrial organic matter derived from land plants offers an alternative source. The evolutionary level and kind of contributing source organisms may be of decisive influence on the type and amount of petroleum generated in a certain source rock. Therefore, one must consider the evolution of the biosphere in connection with the formation of petroleum.
KeywordsSource Rock Early Cretaceous Land Plant Middle Devonian Early Carboniferous
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