Klondike Hills, Southwestern New Mexico: Example of Laramide Deformation

Michael G. Rupert, Russell E. Clemons

Complex structural deformation in the Klondike Hills has been cited as evidence for extending the western Overthrust belt through southwestern New Mexico. The most prominent structural feature in the Klondike Hills is the northwest-trending Cedar Mountain fault zone, which displays both vertical and lateral movement. Upper Paleozoic rocks in the northeast block have been placed next to Precambrian granite and lower Paleozoic rocks on the southwest side. After removal of a post-Oligocene 25° northeast tilt, the Cedar Mountain fault is vertical to steeply northeast dipping. Left-lateral displacement is suggested by drag folding in the Mississippian rocks northeast of the fault. Wrench faulting is also implied by widespread, extreme brecciation and the braided pattern of Cedar Mountain splay faults. The area south of the Cedar Mountain fault is characterized by two levels of low-angle thrusting offset by younger high-angle faults. The lower thrust fault placed older strata on younger with underlying beds locally overturned. The upper thrust fault placed younger rocks on older with varying amounts of section tec onically eliminated as the near bedding-plane fault gradually cut upsection. A small klippe north of the Cedar Mountain fault zone may be due to transpression at a bend in the fault or a large slide off the uplifted southern block.

Structural features in the Klondike Hills more closely resemble a basement cored block uplift model than a regional overthrust model. The general relations are similar to those described in the Florida Mountains, 60 km to the east, by G. A. Brown and R. E. Clemons in 1983.

AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.