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The palynoflora of the Fossil Butte Member of the Green River Formation was studied to relate the flora and climate to the genesis of oil shale in ancient Fossil Lake. Samples were collected from measured sections representing open and marginal lacustrine environments. These samples were analyzed using standard palynologic and visual kerogen techniques.
Evidence from the palynoflora suggests that during deposition of the Fossil Butte Member, the climate was in transition between humid, subtropical to a cooler, drier, warm temperate one with moderate fluctuations during various episodes of deposition. Additional evidence indicates that moist lowlands and flood plains existed around Fossil Lake, with upland forests on the surrounding ridges and mountains. Streams originating in the highlands supplied water to Fossil Lake and the surrounding vegetation. The age of the palynoflora along with K-Ar age determinations indicate that deposition of oil shale in Fossil basin was contemporaneous with deposition of the evaporite facies of the Wilkins Peak Member in the Green River basin. This suggests that factors affecting oil shale deposition i the two basins were locally, as well as regionally, controlled. The dominance of amorphous kerogen in the kerogen samples suggests an algal origin for the majority of the oil shales.
The palynoflora, the kerogen type, and the stratigraphic relationships indicate that the deposition of oil shale in Fossil basin was due to local climatic and environmental conditions.
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