LARAMIDE DEFORMATION IN THE TUCUMCARI STRUCTURAL ZONE, EAST-CENTRAL NEW MEXICO

Northeastern New Mexico is characterized by an apparent lack of structural complexity. However, there is an area of unrecognized deformation in the Quay County area.

From Tucumcari to the southwest, there is a northeast-trending zone of structural complexity that we term the Tucumcari structural zone It is bounded on the northwest by the Newkirk anticline and on the SE by the Bonita fault zone. Most structural features within this zone trend NE, whereas NW-trending structures terminate the Tucumcari structural zone to the north. These structures include a number of folds such as the Newkirk anticline, the Palomas basin and the Quay anticline. The Bonita fault zone is the best studied structure in the area, but there are faults that have been overlooked, including the Tucumcari Mountain fault and unmapped faults near Pyramid Mountain and under Plaza Larga..

The most precise age for the Tucumcari structural zone can be derived from the Bonita fault zone. These faults cut through the Upper Cretaceous Bridge Creek Member of the Greenhorn Limestone (at youngest earliest Turonian in age), but they do not disrupt the Neogene Ogallala Formation. This age, together with their NE trend, indicates that they are most parsimoniously considered to be related to the Laramide orogeny. Laramide buckling in the Tucumcari structural zone was a result of southeastern tilting affecting an area between two NE-trending uplifts that had healed faults with a NE trend. There are a number of NE-trending buckles (folds and/or faults) across the Pecos slope in southeastern New Mexico that are presumably a crustal response to the same stress pattern in a more unconfined terrane.