Abstract
We present an interpretation of seismic-reflection data from the Playas and Hachita valleys of southwestern New Mexico which places new constraints on the geometry of structures responsible for Laramide shortening, and subsequent Basin and Range extensional structures. With seismic interpretation tied to well data and gravity modeling, we address aspects of the debate that still surrounds the question of whether Laramide shortening was accommodated by “thin-skinned” thrusting along a regional décollement or by basement-involved block uplifts. Our interpretation suggests that shortening was at least in part accommodated with low-angle, basement-involved thrusts. Subsequent extension occurred on range-bounding normal faults that become listric near 10-km depth. The relative lack of recent basin fill in the Playas Valley, and particularly the Hachita Valley, suggests either that uplift of the mountains along normal faults has been relatively recent or that extension has only just compensated for earlier shortening, and has yet to create deeply subsided basins.
