New Mexico Geology Redefines Ancha Formation

by Rachel Armstrong

SOCORRO -The latest issue of New Mexico Geology focuses on the "Redefinition of the Ancha Formation and Pliocene-Pleistocene deposition in the Santa Fe embayment in north central New Mexico." The article states that new geologic mapping, sedimentologic field studies, and geochronologic data indicate that the Ancha Formation ranges from 33 to 295 ft. in thickness. The Ancha Formation is a locally important, albeit thin (148 ft.), aquifer for domestic water wells south of Santa Fe.

Another article presents a histological study of the ray Pseudohypolophus mcnultyi (Thurmond) from the Late Cretaceous of central New Mexico. The study states that the Pseudohypolophus lived along the margins of the North American Cretaceous Interior seaway. The teeth of Pseudohypolophus, common in shallow water marine deposits in New Mexico, Texas, Georgia, Nebraska, South Dakota, Wyoming, and North Carolina, are studied by paleontologists and compared to other samples.

The latest in a series of New Mexico State Park articles discusses the history and geology of Navajo Lake State Park, which is located in the Four Corners region of New Mexico. The park contains the second largest reservoir in the state. Navajo Dam was built by the U.S. Bureau of Reclamation for flood and sediment control, as well as recreational usage. The reservoir provides water to the Navajo Indian Irrigation Project, which is one of the many participants in the Colorado River Storage Project.

New Mexico Geology is published quarterly by New Mexico Bureau of Geology and Mineral Resources, a service division of New Mexico Tech. A subscription to the award-winning journal costs $12 per year, or $22 for two years. Individual issues may be purchased for $3.50 each. For more information about New Mexico Geology, or any other NMBGMR publications, write to the Bureau Publication Office, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, call (505) 835-5410, or visit the Bureau's website at http://geoinfo.nmt.edu.