Chemical and isotopic constraints on source-waters and connectiviity of basin-fill aquifers
P. Drakos, K. Sims, J. Riesterer, J. Blusztajn, and J. Lazarus
Selected wells and surface water sources in the Taos Valley have been sampled and analyzed for major anions and cations, trace metals, 87Sr/86Sr, 3H, δ2H, and δ18O. 87Sr/86Sr varies from 0.7074 to 0.7156, indicating water-rock interaction with variable source rocks. Because these waters have relatively enriched 87Sr/86Sr it is likely that the Pennsylvanian carbonates and granitic basement rocks have contributed significantly to their Sr isotopic compositions. Tritium results indicate that recharge to the shallow aquifer occurs on a time scale of < 5 to 10 years, but that recharge to some deep alluvial wells and Agua Azul (Servilleta Formation) wells occurs on a time scale of > 50 years. Recharge into the mountain front fractured bedrock aquifers occurs on time scales ranging from < 5 to 10 years to > 50 years. δ2H and δ18O data suggest that some deep basin-fill aquifer wells have received older (Pleistocene) recharge, whereas other deep wells have received Holocene recharge. Some compartmentalization of the Tertiary aquifer system is indicated by these results. This aquifer compartmentalization is likely caused by intrabasin faults such as the Seco fault that exhibit significant offset.
- Drakos, P.; Sims, K.; Riesterer, J.; Blusztajn, J.; Lazarus, J., 2004, Chemical and isotopic constraints on source-waters and connectiviity of basin-fill aquifers, in: Geology of the Taos Region, Brister, Brian S.; Bauer, Paul W.; Read, AdamS.; Lueth, Virgil W., New Mexico Geological Society, Guidebook, 55th Field Conference, pp. 405-414.