Abstract

The 400-mile-long Amarillo/Wichita Mountains thrust and fold belt, also called the “Southern Oklahoma Aulacogen,” is seen in detail in the extensive aeromagnetic maps flown by Applied Geophysics, Inc. 25 to 30 years ago. Much has been written about the geology of this system, both the overall extent as well as myriad details along its length by geologists in both Oklahoma and Texas over the years, but some new features of the system seen on the magnetic maps have never appeared in the literature. For example, the apparent thinning and dying out of this system to the west in Union County, New Mexico, just west of the Texas Panhandle is visible on the magnetics, as is the probable strike-slip offset of the system at its east end in northeast Texas. In the latter locality it may have been translated 410 miles to the northeast by a regional strike-slip fault and ended up in southeast Missouri. Thus, the Broxton Fault of Oklahoma may have its extension as the St. Genevieve Fault in the St. Francis Mountains of Missouri.

The magnetic maps indicate that an east-west strike-slip fault, the “Cambridge Fault,” offsets the Wichita Mountain block in right-lateral fashion along the south line of Beckham and Washita Counties in Oklahoma. This fault is 70 miles north of, and parallel to, the similar east-west - trending Matador Arch, which may also have had strike-slip movement. To the south, the location of the Marietta Basin on top of the Wichita Mountain block is plainly visible on the magnetics, as is the location of the Ardmore Basin in front of it.

Arguing from a strictly geological standpoint and relying on many key articles from the recent geological literature, the Wichita Mountains were raised by thrusts, and the buried Amarillo Mountains, because of their proximity and colinearity with the Wichita Mountains would necessarily have been raised by thrusts as well, in spite of fairly recent papers that show only vertical faults there. Furthermore, by adding a long listric segment to the Mountain View thrust fault shown on the COCORP seismic line and extending the Muenster-Waurika Fault down to the north as a back-thrust, it is seen that the Wichita Mountain block is probably a gigantic V-shaped “pop-up block.” This makes it similar to the Front Range of the Rockies in Colorado, the Uinta Mountains in Utah, and the Central Basin Platform in the Permian Basin of Texas, among others.

Since the Amarillo-Wichita Mountain system is a classical thrust-fold belt, there may be many oil and gas fields within this belt similar to those in the prolific western U.S. thrust-fold belt. Only one such field has been found on top of the uplift: Cottonwood Creek, discovered in 1987 in Carter County, Oklahoma, by CNG Production Company (New Orleans), but there should be others on both sides of the Oklahoma-Texas line.