New Mexico Geological Society Annual Spring Meeting — Abstracts

The middle Rio Grande valley is presently experiencing a rapidly growing population. Large cities in the western interior, such as Albuquerque, face two serious problems: water resources, and potential seismic hazards related to active tectonics. Following from the initial work of Connell (1995), this study performs a tectonic geomorphologic analysis and field mapping of specific portions of the Sandia mountain front and piedmont (Pino Embayment) east of Albuquerque, NM. Results are used to better understand the structural and hydrostratigraphic setting of the Albuquerque Basin. Drainage basins on the west facing Sandia mountain front suggest highly variable rates of offset, both in time and space, on the range front fault. A detailed field map (1:12,000) of the Pino Embayment helps corroborate these morphometric results. Quaternary stratigraphy in the Pino Embayment is composed of five allostratigraphic fan and terrace deposits. Field and laboratory soil analysis helps to constrain the relative ages of the Quaternary deposits at a resolution higher than initially proposed by Connell (1995). In summary, the stratigraphy of the Pino Embayment is dominated by a large alluvial fan designated as the Q2 deposit, which is estimated to be middle Pleistocene in age. Progressively younger deposits are inset into the proximal regions of Q2, but bury distal regions. The mapping clearly shows only a thin veneer of Quaternary deposits burying a granitic bedrock pediment that locally is exposed at the surface. These results demonstrate that the Pino Embayment is not underlain by an alluvial aquifer. However, vegetation lines, natural surficial springs, low scarps cutting Q2, and highly fractured bedrock all suggest movement of groundwater through Quaternary fault systems. Further work will better constrain the role of the structural setting and Quaternary stratigraphy in determining potential recharge from the Sandia mountain front to the Albuquerque aquifer.