New Mexico Geological Society Annual Spring Meeting — Abstracts

Compilation of new isopach maps in southern New Mexico for four lower Paleozoic sedimentary successions (Bliss-El Paso, Montoya, Fusselman, and Devonian strata) indicates the presence of pronounced dextral deflections in the isopach patterns for these strata, particularly in data-rich areas near their northern pinch-outs. These deflections occur across fault systems of known or suspected Laramide and, in the east, Ancestral Rocky Mountain ancestry. The magnitude and interpreted origin of the best-defined of these dextral deflections are: Hot Springs fault system near Truth or Consequences (~25 km, mostly Laramide); Engle Basin (32-36 km, mostly Laramide; includes ~26 km value for Hot Springs fault system); Palomas Basin (57-70 km, ~26 km of which is attributed to Laramide slip on the Hot Springs fault system; the reminder is of unknown origin; Tularosa Basin (~40 lm, largely tectonic in origin but the relative contributions of Laramide and Ancestral Rocky Mountain slip are unknown). Additional deflections may exist across the Pedernal uplift but are in need of further study.

The cumulative dextral deflection of Lower Paleozoic isopachs in southern New Mexico is ~100-110 km, not counting possible additional deflections associated with the Pedernal uplift. This is approximately equivalent to the magnitude of dextral separation of Proterozoic rocks and basement aeromagnetic anomalies in northern New Mexico, which suggests that the Proterozoic offsets may be entirely Phanerozoic in origin.