New Mexico Geological Society Annual Spring Meeting — Abstracts

The area from Sierra Ladrons to Mesa Sarca was initially interpreted to be a section of the western uplifted and eastward directed Comanche thrust belt. Subsequent post-compression relaxation and rift-related extension resulted in two phases of normal faulting. Recent structural and tectonic interpretations of the surrounding region suggest the area may have been affected by Laramide vertical uplift and gravity sliding, high-angle reverse faulting, strike-slip (wrench) faulting, and/or low-angle faulting. Rift-extensional faulting may be either listric or domino style.

I am mapping the relations of Precambrian and upper Paleozoic strata to faults and folds to determine style(s) of structural deformation. Field work emphasizes structural style and kinematic indicators. These kinematic indicators are: (1) slickensides, (2) chattermarks, (3) fault breccia fabric, (4) fold geometry, (5) fault-fold spatial relationship, (6) offset stratigraphy (channel sands), and (7) tension crack orientation.

Early field work revealed a complex variety of structures and kinematics which indicate differing styles of deformation across the area. As a whole, upper Paleozoic strata dip westward 5 to 350. West-directed gravity sliding, resulting from uplift of the Sierra Ladrons, occur s in the southern part of the field area. Northwest of the Ladr on-Paleozoic contact and south of Navajo Gap, a series of north-northeast to northeast-trending gentle folds laterally converge northward and translate into a north-northeastward-trending strike-slip fault. Between Navajo Gap and Coyote Draw (Red Tanks Arroyo), strata are highly faulted by a series of closely spaced north to north-northeast-trending, scissor-style, right-and left-lateral strike-slip faults. Northward these faults die out within a northwe st-trending and plunging series of tight folds. North of Coyote Draw, these folds are separated from very highly deformed Per mian strata by the steeply eastward-dipping to vertical Comanche fault. At the east foot of Mesa Sarca, south-plunging, anticlinal, lower Pennsylvanian strata occur in down-to-east normal(?) fault contact with south-plunging synclinal lower Permian strata. Immediately east of these folds occurs highly faulted (normal, low-angle, reverse, and strike-slip) strata intruded by basaltic dikes, occasionally in swarms.