PALEOCURRENT ANALYSIS AND SEDIMENTOLOGY OF THE MAROON FORMATION, GUNNISON, PITKIN, AND SUMMIT COUNTIES, COLORADO, USA

The Pennsylvanian-Permian Maroon Formation is a 7,000 to 8,000 foot thick succession of interbedded red sandstone, conglomerate, siltstone and shale, with rare limestone. It conformably overlies the Pennsylvanian Minturn Formation to the east and the Gothic Formation to the west, and is unconformably overlain by Mesozoic rocks. The Maroon Formation is time correlative to the Paradox Formation in the Paradox Basin, the Fountain Formation in the Denver Basin, and the Sangre De Cristo Formation in the San Luis Basin. The Maroon Formation has been interpreted as a fluvial deposit draining two major highlands into the Central Colorado Trough. The Central Colorado Trough has been interpreted an asymmetrical basin bounded on the east and west by the Ancestral Rocky Mountains. The Ancestral Rocky Mountains were composed of several uplifts, primarily the Front Range uplift to the east and the Uncompahgre uplift to the west. Several smaller uplifts have been hypothesized, identified and mapped, including the Apishpa, Ute Pass, and Sawatch uplifts. Measured sections of outcrops of the Maroon Formation in Gunnison, Pitkin, and Summit counties were made during the course of this study to evaluate lithofacies and their distribution throughout the Central Colorado Trough during the late Pennsylvanian and early Permian time. Paleocurrent indicators such as clast imbrication, cross stratification, trough cross stratification, and scour and fill structures were measured in beds throughout the measured sections to evaluate the presence of an ancestral Sawatch uplift in the center of the Central Colorado Trough. Circular statistics of the acquired paleocurrent data enabled creation of rose diagrams of paleocurrent directions for each measured section throughout the study area.