Early Permian seaways in the American Southwest

Abstract

Lower Permian marine strata in the American Southwest (Arizona, New Mexico and Texas, USA) identify three extensive marine seaways, one of Wolfcampian age and the other two of Leonardian age. These are strata deposited on the Mogollon shelf and in the Holbrook basin of Arizona, the Pedregosa basin of Arizona-New Mexico and northern Mexico, the Orogrande basin of New Mexico, the Delaware basin of New Mexico-Texas and the Midland basin of Texas. Age control of these strata, based primarily on fusulinids and conodonts, including new conodont data presented here, correlates Wolfcampian (mostly Asselian to Sakmarian) marine strata from the Pedregosa basin to the Midland basin, lower to middle Leonardian (upper Artinskian to mid-Kungurian) marine strata that extend from the Mogollon shelf to the Delaware basin and upper Leonardian to lower Guadalupian (upper Kungurian to lower Roadian) marine strata that extend from the Mogollon shelf to the Midland basin. Active regional Ancestral Rocky Mountain tectonism affected Wolfcampian marine deposition by providing accommodation in which to preserve both non-marine and marine facies within multiple transgressive-regressive sequences associated with the most extensive part of the late Paleozoic ice age, when global sea level would have been low. In contrast, two Leonardian seaways were likely driven by global tectono-eustatic events. Identification of the three Early Permian seaways in the American Southwest underscores the need for more precise correlations as well as integrated sequence stratigraphic interpretations of the deposits of these seaways from Arizona to Texas.