New Mexico Geological Society Annual Spring Meeting — Abstracts

A study for the Taos Soil and Water Conservation District has plotted most of the water wells in Taos County, north and west of the town of Taos. Accurate on-the-ground locations of over 300 water wells, using a GPS receiver, have provided more precise surface locations and topographic information map elevations. State Engineer Office static water level data and landowner information were then used to calculate a more accurate groundwater table elevation. Arc-View mapping programs were used to plot data and provide a medium for continued updates.

A contoured map of water table elevation west of the Rio Grande Gorge shows southeast dip of about 50 feet/mile of the groundwater table from the Colorado border to the south edge of Taos County with discharge tied to the river water level in the Rio Grande Gorge.

Detailed mapping in the Carson area shows water-producing zones in the lower Servilleta basalt, clastic interbeds within the lower Servilleta and in the underlying Santa Fe Group. The water table is controlled by the depth of the nearby Petaca Canyon where springs and riparian vegetation tie to nearby well water levels. Sapping by groundwater seepage is probably causing erosion of this enlarged “dry” canyon.

The water table east of the gorge dips southwest and west toward the river level at about 50 feet/mile with minor flexures along the Arroyo Seco drainageway through Las Colonias and along the Rio Pueblo. Down-to-the-west faulting at Los Cordovas and the Town of Taos landfill appears to drop the water table down quickly across this fault.

Cross sections made using driller’s logs show clear correlations between basalt layers (and clastic interbeds) and allow faults to be recognized. A major structural feature is the Gorge Arch trending NE-SW, with a width in excess of five miles and a structural uplift in excess of 200 feet. This arch has uplifted in Quaternary time and is probably rising today. This feature is possibly a result of rifting and wrench-related tectonism.