Magnetotelluric observations in the western Ouachita Mountains, southeastern Oklahoma

The first magnetotelluric (MT) analysis of the Ouachita Mountains region is presented. Magnetotelluric data acquired at 19 sites along a 60-km profile in southeastern Oklahoma were used to image the western extension of the Ouachita Mountains and to determine the poorly known subsurface interaction between the Pennsylvanian Tishomingo-Belton uplift and the subsurface extension of the exposed western Ouachita Mountains. Drill-hole data, geologic mapping, seismic reflection profiles, and 1-D and 2-D MT-derived models indicate that lying beneath the low-resistivity Gulf Coastal Plain sediments are 2-3 km of deep-water lower Pennsylvanian (Jackfork Group) sediments and 6-8 km of Ouachita facies Lithologies, mainly consisting of the Stanley Group. Beneath the profile's northern section are 2-4 km of Atoka Formation sediments. probably deposited within the Arkoma basin. that underlie thrusted zones of the Stanley Group. The most unique feature is a high-resistivity zone beneath stations 7-9, interpreted to be Precambrian/Cambrian granite similar to that exposed in the Tishomingo-Belton uplift. A deep (5-6 km) low-resistivity zone that may represent the northern border of the subsurface extension of the Broken Bow uplift is located along the Texas/Oklahoma border; however, this zone is not required by the MT data.