Tectonics of the Four Corners region of the Colorado Plateau
— Lee A. Woodward, Orin J. Anderson, and Spencer G. Lucas

The Four Carom region is in the central part of the Colorado Plateau, a structurally unique province that has undergone only moderate Laramide (Late Cretaceous-Paleogene) deformation compared with surrounding areas. This province is characterized by monoclines separating Large, lined blocks, with basins and asymmetric uplifts forming the major tectonic elements. The north-trending Monument and Defiance uplifts and the circular San Juan dome are hounded by the Blending, San Juan. and Black Mesa basins. The Four Corners platform, of intermediate structural height, connects the Defiance uplift with the San Juan dome. and separates the Blanding and Sun Juan basins- The tile, La Plata, and Carrizo intrusive centers are composed mainly of intermediate felsic porphyries that loon laccoliths, stocks, necks, dikes, and sills. The structural and tectonic features are the results of northeast movement of the Colorado Plateau during the Laramide orogeny. Two phases of crustal contraction have been proposed, with the first phase of maximum compressional stress oriented E-W to NW-SE and the second oriented NE-SW to NS. North-trending structures were inferred to he caused by the first phase and west-trending features caused by a second phase. Recent work, however, has indicated that there is no systematic variation in initiation and cessation of movement on individual Laramide structures. Northeast movement of the Colorado Plateau resulted in left shift on the north side of the plateau where it is hounded by the Uinta uplift and right shift on the east side adjacent to the Nacimiento uplift. East-trending, regional piercing lines formed by stratigraphic pinchouts, truncations, and facies changes of Paleozoic and Mesozoic strata in New Mexico allow a maximum of 5-20 km of Laramide right-lateral offset along the east side of the Colorado Plateau. Nonetheless, some workers have proposed 60-170 km of Laramide right slip along a north-trending zone up to 100 ken wide on the east side of the plateau, even though the data clearly indicate this is an excessive estimate, Right shift within the plateau occurred along the sinuous. north-trending Defiance monocline.