New Mexico Geological Society Annual Spring Meeting — Abstracts

In 2015, the Mora-Wagon Mound Soil and Water Conservation District launched a hydrogeology project designed to partner with the ongoing Union County Hydrogeology Project. These two projects together are aimed at developing a better understanding of regional groundwater relationships in northeastern New Mexico. The Mora-Wagon Mound SWCD covers approximately the eastern two-thirds of Mora County, from the front range of the Sangre de Cristo Mountains to the Canadian River valley. Preliminary data were collected during 2015 and include biannual static water level measurements from 25 wells, basic water chemistry from eight wells, radiocarbon dates from 10 wells and geologic mapping along the I-25 corridor.

Initial water level measurements indicate the presence of three discrete groundwater horizons: a shallow zone at 10-40’ below land surface (bls), an intermediate zone 150-300’ bls and a deep zone greater than 350’ bls. The intermediate zone primarily corresponds to the Cretaceous Dakota Group. After an unusually wet summer, hydrographs for a subset of the wells appear to document recharge into the shallow groundwater horizon.

In order to assess subsurface geologic complexity, five petroleum well geophysical logs from the central part of the SWCD area were examined. Tentative correlation of rock units among these logs suggest the subsurface geology is fairly complex, with structural relief and/or paleotopography developed on the top of the Jurassic Morrison Formation near the village of Wagon Mound. This complexity is also supported by the distribution of radiocarbon dates across the project area and wells that appear to document summer recharge. Preliminary geologic mapping documents extensive fracturing of exposed bedrock of the Dakota Group, yielding information on potential flowpaths for groundwater in areas where the Dakota Group is the primary aquifer in the subsurface.

Earlier work by the New Mexico Environment Department hypothesized that recharge to the Wagon Mound springs, west of the village, is provided by melting snowpack from the Turkey Mountains to the south. The orientation of fractures documented during mapping is dominantly north-south to northwest-southeast, whereas the hinge of the Turkey Mountain anticline (located near the center of the project area) is oriented northeast-southwest. This contrast between a local structural feature and the local fracture patterns raises questions regarding the relationship between Turkey Mountain snowpack and local spring recharge.