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Abstract Depositional-system studies of the predominantly Wolfcampian Cutler Formation, in the Uncompahgre (Paradox) Basin have identified five fluvial and two marine facies and associated eolian deposits. The fluvial facies progressing outward from the source area, are: proximal braided, which consists of a fan-building sequence and a very coarse grained fan-head trench sequence; medial braided; distal braided; 50 percent meandering; and 100 percent meandering. The braided facies outline three large (40 to 60 km radius) fluvial or wet fans. The Gateway fan, in the northern part of the basin, was deposited to the southwest off the Uncompahgre highland, the San Miguel fan, in the central part of the basin, was deposited off the southern end of the Uncompahgre highland, and the Piedra fan, in the southeastern part of the basin was deposited west of the San Luis highland. The marine and eolian deposits occur only in the northern part of the basin adjacent to and intertonguing with the Gateway fan. Transition of the streams from distal braided to coarse-grained meandering occurred at the toe of this fan, near sea level. Seaward of the toe, meandering became more common. A marine transgression occurred early during fan development resulting in deposition of the limestones and shales of the Rico, or of the Elephant Canyon Formation of Baars. In a later marine invasion from the southwest, limestones, sandstones, and shales were deposited that are lateral equivalents to the Cedar Mesa Member of the Cutler Formation. The eolian rocks are closely related stratigraphically and geographically to the marine facies and are considered coastal dune-field deposits. The San Miguel and Piedra fluvial systems coalesced approximately along the present course of the Animas River. Transition of both systems from distal braided to 50 percent meandering occurred along their southwest flanks and may also have occurred along their northeast flanks.
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