Deposition in the late Paleozoic Oquirrh basin of northwest Utah produced as much as 7.5 km of limestone and sandstone. Study of Upper Pennsylvanian and Lower Permian lithofacies, trace fossils, and body fossils relative to a time framework determined by fusulinid biostratigraphy reveals a spatial mosaic of depositional environments which shifted through time.

The Oquirrh basin changed in form from a broad, topographically subdued, shelf area in the Middle Pennsylvanian to a northwest-trending topographic basin in the Late Pennsylvanian. Water depths may have reached 300 to 400 m. Coarse conglomerates, commonly composed of older Oquirrh Group clasts, are common in latest Pennsylvanian and early Wolfcampian deep-water deposits. They record rapid lithification, uplift, and erosion of the margins of the trough, and imply that the Oquirrh basin was bounded by active northwest-trending high angle faults. The faults, with offset rates of about 25 cm/1,000 years, were apparently initiated in the Late Pennsylvanian, and became inactive by the late Wolfcampian. The upper Oquirrh Group records the passive filling of the remnant graben-like trough.

angle

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