Abstract

The Paradox Basin is a tectonic depression of late Paleozoic age that is generally defined by the geographic extent of halite deposited within the Middle Pennsylvanian Paradox Formation. The Paradox Basin began to subside in the Middle Pennsylvanian concomitant with uplift of the Uncompahgre Highlands of the Ancestral Rocky Mountains. This source shed thick deposits of arkosic sediment into the basin. As much as 9000 ft of Middle and Upper Pennsylvanian evaporites, shale, and limestone, and at least 6000 ft of Permian marine and continental strata are present in the basin. The Paradox Basin continued as a major locus of deposition through and after the Permian and into the Triassic.

The Permian Cutler Formation (undivided) consists of arkosic units shed off the Uncompahgre Highlands in the northeastern part of the Paradox Basin. In the central and western parts of the Paradox Basin the Cutler Group is divided into five formations (in ascending order): the lower Cutler beds (including the Halgaito Formation), Cedar Mesa Sandstone, Organ Rock Formation, De Chelly Sandstone, and White Rim Sandstone. Rocks within the Cutler were deposited in a variety of alluvial fan, braided stream, eolian, and marine environments. The location of the Paradox Basin both near the equator and along the west coast of Pangea contributed to its hot, dry climate; however, seasonal precipitation from a developing monsoonal climate system modified the generally arid climate during deposition of some units. Although advances have been made in the interpretation of depositional settings, detailed correlations and sequence analysis continue to be inhibited by complex facies changes within continental rocks, areas of no outcrop, and the extreme local variations in subsidence due to salt tectonics.