The Green River Formation is easily recognized by its light color and
continuous bedding, in strong contrast to the red, discontinuous,
variegated Wasatch Formation below. The Green River Formation can be
thought of as a gigantic lens of lacustrine sediments enclosed in the
fluvial Wasatch Formation. The name Green River Formation is applied to
all of the roughly contemporaneous deposits laid down in lakes of Utah,
Colorado, and Wyoming. It is probable that at one time or another all of
these lakes were connected.
Oriel and Tracey (1970) have divided the Green River Formation of the
Fossil Basin into two members: the Fossil Butte Member and the Angelo
Member.