The Park City Group is composed of, in ascending order, the Kaibab Limestone, Plympton Formation, and Gerster Limestone. The Kaibab is fossiliferous limestone and dolomite; the Plympton is chert, dolomite, and siltstone; and the Gerster is fossiliferous limestone with minor amounts of siltstone. The age range is late Artinskian (late Leonardian) to early Guadalupian (Wordian). The succession of lithofacies constitutes two transgressive cycles. The earlier transgressive phase is represented by the Kaibab Limestone and lower Plympton Formation, and the later phase is represented by the upper Plympton Formation and Gerster Limestone. A northwest-trending high (part of the Cortez-Uinta axis) affected the sedimentation pattern.