Geologic studies of oil shale were pioneered by W. H. Bradley in 1929. His basic model for the genesis of oil shale called for a deep stratified lake in which anaerobic conditions in the hypolimnion ensured the preservation of organics and accounted for the finely laminated character of the oil shale. Until recently, studies involving the depositional environment and genesis of oil shale were based on the stratified lake model.

In 1973 Eugster and Surdam presented an alternate model (playa lake model) that accounted for the origin of oil shale in a shallow lake fringed by broad mud flats or playas. The playa lake model accounted for observed shallow-water sedimentary structures and evidence of a low topographic gradient. This abrupt change in basic concepts was not readily accepted by many workers. Views have polarized, primarily because of the variety of depositional conditions that existed in separate but geographically related basins of deposition.

This polarization will not be resolved until a more adequate and comprehensive model is developed. It must account for most of the pertinent observations, including preservation of organic matter, sedimentary structures, carbonate deposition and diagenesis, vertical and lateral facies relationships, and paleontology of the Green River Formation, all of which are critical to an understanding of oil shale genesis.

End_of_Article - Last_Page 458------------