Geohistorical Analysis of Paradox Basin: ABSTRACT

Abstract

The Paradox basin is an elongate sedimentary basin, asymmetric in profile, extending across common corners of Utah, Colorado, Arizona, and New Mexico. Subsidence of the basin began in Desmoinesian time and was coincident with the development of the Ancestral Rocky Mountains. The Uncompahgre uplift formed the northeast boundary of the basin during Pennsylvanian and Permian times. Formation thicknesses and lithologies were obtained from lithologic and radioactivity logs from various parts of the basin. The stratigraphic column at each well, restored through the Upper Cretaceous, was backstripped and decompacted to reconstruct its depositional history. Decompacted geohistory diagrams and residual (tectonic) subsidence curves were then generated for each well. The Mobil 1 McCormick well, drilled in 1977, penetrates Pennsylvanian strata beneath reverse-faulted granitic basement; this indicates that the basin was flexed down in response to Pennsylvanian and Permian thrust faulting along the flank of the Uncompahgre uplift. However, close correspondence of the residual subsidence curves to theoretical thermal subsidence curves indicates that the basin formed by crustal extension. Consequently, development of the basin may have involved crustal stretching (transtensional?) beneath the basin floor, followed by thrusting (transpressional?) along the flank of the Uncompahgre uplift. End_of_Article - Last_Page 854------------