Proterozoic and Pre-Cenozoic History of the Sierra Grande Uplift and its margins: A Key Piece of the Ancestral Rocky Mountains
— Thomas E. Ewing

A new compilation of wells penetrating or approaching basement combined with a comprehensive review of existing literature result in new observations on Proterozoic, Late Paleozoic and later structures in northeastern New Mexico, southeastern Colorado and adjacent states. Proterozoic granitic rocks (1400-1340 Ma) underlie much of the area, forming a broad rim around the Panhandle volcanic rocks of the same age; this may represent differential uplift of a shallow batholith, which is overlain by its own volcanic cover under the Texas Panhandle, but has been eroded to the west and largely removed by 15 km of erosion in central New Mexico. Late Paleozoic uplift of the Ancestral Rocky Mountains formed a complex high with several prongs, bounded on one or both sides by major faults. The Cimarron-Bravo uplift on the south and Apishapa uplift on the north form a two-sided outward-verging high, with a shallow proto-Raton basin between them. A zone of isolated basins and uplifts lying to the south in the Tucumcari and Palo Duro basins may represent a wrench fault complex. Laramide formation of the Raton basin reactivated the western part of the Cimarron uplift as a north-verging structure and created the sharp-crested Sierra Grande uplift.