New Mexico Geological Society Annual Spring Meeting — Abstracts

Lithologic and geophysical data from the deep ground water exploration program in the Taos area are used to delineate variations in thickness and extent of the Upper, Middle, and Lower Servilleta basalts and underlying Tertiary basin fill sediments in the southern San Luis Basin. Servilleta basalts increase in thickness from south to north within the study area; they are absent in BOR1, present as a single thin flow BOR3, and present as three multiple-flow sequences at RP2500 and the Airport well (Fig. 1). Servilleta basalts can traced eastward in well K2, Tract B Tip and BOR5, where the Servilleta (?) basalt is downdropped within a mountain front graben. In the majority of wells drilled to date, Tertiary fluvial sediments appear to small and large scale show fining upward sequences, indicating deposition in an environment relatively free of tectonic influences. However, sediments in BOR3 are generally much coarser grained and appear to show small and large scale coarsening upward sequences, indicating that deposition may have been controlled by motion on a proximal fault (fown Yard Fault?).

The eolian Ojo Caliente Member of the Tesuque Formation varies in apparent thickness from thin or absent at BORI to greater than 1000 ft at RP2500 to 340 ft at the Airport well. Elevation of the upper contact of the Chama-EI Rito Member of the Tesuque Formation is highly variable, ranging from below 4200 ft (RP 2500 total depth) to 6060 ft (BOR3). It is unclear if these variations are due to tectonic disruption or depositional processes. BOR3 (TD=2110') is unique in the respect that it is the only well that penetrates through Chama-El Rito sediments into the underlying Picuris Formation at the base of the Tertiary, indicating that the Tertiary section is relatively thin at that location.