STRATIGRAPHIC AND PALEO-ENVIRONMENTAL STUDY AND INTERPRETATION OF THE CHINLE FORMATION, WOLVERINE PETRIFIED WOOD AREA, GRAND STAIRCASE-ESCALANTE NATIONAL MONUMENT, UTAH

The Chinle Formation exposed around the Wolverine Petrified Wood area of the Grand Staircase-Escalante National Monument in southern Utah preserves a sequence of fluvial and lacustrine deposits interbedded with paleosols. There are six readily recognizable members of the Chinle formation present in the study area. From the base to the top of the exposure the members are the Shinarump conglomerate, the Monitor Butte member, the Bluewater Creek member, the Petrified Forest member, the Owl Rock member, and the Rock Point member. Within this sequence are three intervals of fossil-bearing strata. The lowermost fossil bearing interval occurs in the Monitor Butte and Bluewater Creek members as low as 2.7 meters and as high as 18.1 meters above the base of the Chinle exposure and contains limited amounts of petrified wood as well as fossil leaf casts and carbonized leaves in light green siltstone. The upper two fossil bearing intervals occur in the Petrified Forest member of the Chinle formation. The middle fossil bearing unit crops out at an average 52.8 meters above the base of the Chinle exposure and preserves large amounts of permineralized wood as well as vertebrate bone fragments in sandstone. The uppermost fossil bearing unit crops out as low as 61.6 meters and as high as 82.45 meters above the base of the Chinle exposure and preserves limited amounts of permineralized wood. Paleosols increase upward and record increasingly arid conditions from the time of deposition of the Petrified Forest member to the time of deposition of the Owl Rock member. This climatic shift is congruent with findings by other workers studying the Chinle in other parts of the Colorado Plateau.