REDBEDS IN WYOMING: READING LATE PERMIAN-EARLY TRIASSIC ENVIRONMENTS AND CLIMATES FROM THE RED PEAK AND CROW MOUNTAIN FORMATIONS
The Red Peak Formation, well exposed along most Laramide uplifts in Wyoming, is located stratigraphically below the Alcova Limestone. It is dominated by paleosols and sheet flood deposits. Weathering differences creates couplets of recessive and resistive beds. The sediments fine upward. Few of the paleosols preserve root traces or bioturbation. Within the Red Peak, we notice no trends in ped morphology, though there is a distinct increase in CaCO3 and trends in trace elements up section.
The paleosols of the Crow Mountain Fm. are well exposed at one location near Lander, Wyoming, and poorly exposed in many locations above the Alcova Limestone. At the well-exposed section, paleosols transition up section from discreet simple paleosols to amalgamated complex paleosols. At the base of the section, thin fining upward beds with well-developed peds and no root traces are separated by non-channelized sediment bodies. The uppermost section is amalgamated paleosols and channelized fluvial deposits. The amalgamated paleosols have abundant root traces, shrink-swell traces, and diverse ped morphology.
Descriptions of these redbeds represent the first steps in attempting to reconstruct climate and environments through the Permian and Triassic sections in Wyoming. We interpret changes in the hydrologic regime over time: specifically, greater availability of water at the surface, and more channelization of that water. This may be indicative of changing climate, from arid to semi-arid, as Pangaea recovered from the Permian-Triassic ecological crisis.