Middle-late Proterozoic extension in the Carlsbad region of southeastern New Mexico and west Texas

Abstract

—Extensive bimodal igneous activity occurred in the Middle Proterozoic of North America, affecting areas of Arizona, California, Colorado, Iowa, Kansas, Michigan, Minnesota, Nebraska, New Mexico, Oklahoma, Texas and Wisconsin. We discuss the portion of this activity affecting west Texas and eastern New Mexico. Igneous intrusions formed in west Texas and New Mexico between 1215-1074 Ma. These bodies are exposed or have been penetrated by drilling in the Central Basin platform, Franklin Mountains, Van Horn uplift, Pajarito Mountain and Devils River uplift. Information from previous studies of Precambrian outcrops and wells drilled to the Precambrian are combined with gravity maps to produce a picture of Middle Proterozoic activity in this region. This picture shows that igneous activity occurred in two areas coincident with the Debaca-Swisher terrain and the Delaware aulacogen. The bimodal igneous activity suggests extension. This igneous activity was in part coincident with formation of the Midcontinent rift system and Grenville age tectonic events in Texas. Further geologic and geophysical studies are necessary to understand the Middle Proterozoic of the region and its relationship to Middle Proterozoic tectonics.