Oil shale in the Green River Formation of Wyoming was deposited in shallow water. The sandstones and siltstones spatially associated with oil shale are characterized by mudcracks, ripple marks with flattened crests, ripple marks with mudcracks in the troughs, many burrows and root casts, thinly bedded units with current laminations, and fluviatile channel deposits. The sandstones and siltstones lack graded bedding and other sedimentary structures diagnostic of turbidite sequences.

The assemblage of carbonate rocks associated with oil shale includes dolomicrite with mudcracks, crystal casts, and plant debris; flat-pebble conglomerates; coquinas containing pulmonate gastropods; ooliths and pisoliths; algal bioherms; and mudcracked ostracodal limestones.

Disrupted bedding and a lack of continuous lamination are distinctive of the oil shale in the Green River basin. At some locations oil shale contains abundant ostracodes and insect larvae. The oil shale is closely associated with trona beds in the Wilkins Peak Member of the Green River Formation.

The sedimentological evidence is overwhelmingly in favor of a shallow-water origin for the oil shale in the Green River Formation of Wyoming. This genetic interpretation is consistent with the playa-lake (continental sabkha) model recently proposed by Eugster and Surdam.

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