“Humic” matter was isolated from bitumen extracted from suites of sedimentary rocks varying in lithology and depositional environment and ranging in age from Archean (Onverwacht) to Miocene, the majority of the samples being of pre-Paleozoic age. The molecular properties of the humic matter, as determined by quantitative ultraviolet, visible, and infrared spectrophotometry, vary systematically through geologic time. The secular variations are interpreted as representing major events in the evolutionary history of pre-Paleozoic algae.

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