Depositional Environment of Green River Formation

Raymond Sullivan

Two contrasting depositional models have been proposed for the origin of the lacustrine rocks of the Green River Formation. An open-drainage, stratified-lake model has been largely replaced by a playa-lake setting. However, workers are reluctant to apply the playa-lake model to the predominantly organic-rich sequences of the Green River Formation. The model has been applied primarily to evaporite-rich sequences of the Wilkins Peak Member in the middle part of the formation. Workers generally agree, however, that these deposits were laid down during a more arid period, when Lake Gosiute was at a lowstand and no major drainages were developed in the western part of the basin.

Subsurface stratigraphic relations were not well understood at the time both models were formulated. These studies have shown that widespread fluvial drainages were indeed developed in this part of the succession and that they intertongue with the Wilkins Peak Member. They are represented by the New Fork, Desertion Point, and Cathedral Bluffs Tongues of the Wasatch Formation.

Recognition of numerous and diverse lacustrine sequences indicates that the environment was continuously being modified by climatic and/or tectonic influences. A composite model is, therefore, supported whereby the lakes fluctuated from all extremes depending on the rate of inflow of fresh water into the system. Even during the lowstand of the Wilkins Peak Member, the playa lake was periodically flooded and enlarged during pluvial periods.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.