Isotopic Investigation of Ground Water Resources in the Ojo Alamo Sandstone, Nacimiento, and San Jose Formations, San Juan Basin, New Mexico

摘要

The San Juan Basin, in northwest New Mexico, has vast reserves of strippable, low sulfur coal. Development of the resource will require large quantities of water, from an area where water resources are not abundant. Since surface-water supplies are fully allocated, increased future water demands will have to be met through ground-water development. The study concentrates on the Ojo Alamo, Nacimiento, and San Jose Formations, the aquifers directly above the principal coal unit. Carbon-14 and tritium methods were used to date the ground water in these units. Initial radiocarbon activities were calculated using the models of Vogel, Tamers, Pearson, Mook and Fontes. The observation lends support to the hypothesis of isotopically lighter Pleistocene precipitation. Such lighter recharge was most likely due to a colder mean annual temperature and perhaps increased winter precipitation. A similar change is obtained from noble-gas paleothermometry.