Implications of recent geophysical studies of the Big Hatchet Mountains area, southwestern New Mexico
— David L. Shearer and Kate C. Miller

A detailed gravity survey conducted in the boot heel area of southwest New Mexico provides evidence of steeply dipping (45-65°) faults with intersecting trends beneath the valley fill. Abrupt changes in gravity (up to 30 mgal) measured along the west side of the Little Hatchet and Big Hatchet mountains over a narrow (3-4 km) strip correlates with range-bounding faults delineated previously by seismic data. In contrast to the northwest-southeast orientation of Big Hatchet Mountains and the shallow structures associated with the Hachita Valley, the Bouguer values outline a deep (>3000 m), elongate (-40 km long by 10-14-km wide), north–south oriented basin along the west side of the Big Hatchet and Alamo Hueco mountains. A smaller, northwest-oriented trough is present west of the Little Hatchet Mountains and a strong, positive feature extends northeast beneath the Playas Valley. The results show a clear image of north–south and northwest–southwest-oriented fault blocks and associated, elongate, Cenozoic grabens within the larger Paleozoic-age Pedregosa basin.