A pre-late Wisconsin paleolimnologic record from the Estancia Valley, central New Mexico

Abstract

Sedimentologic and paleontologic analyses of a 10.5 m subsurface section from the Estancia Valley provides a high-resolution paleolimnologic record of a pre-late Wisconsin section that is suspected to represent early through middle Wisconsin time. Relative abundances of ostracodes, foraminifers, Ruppia, and charophytes, along with sedimentologic aspects, depict a time interval characterized by alternating dry and wet playas and shallow saline lakes. The saline lakes exhibit marked evolution from brackish to saline to, presumably, hypersaline conditions. The overall paleoenvironmental conditions are in great contrast to those represented by the overlying full glacio-pluvial sediments of late Wisconsin age.The pre-late Wisconsin section, as a whole, represents cold/dry paleoclimatic conditions. Minor climatic excursions from this norm are recognized, but the section is more notable for its quasistability. The lack of any fresh-water phase during this time implies that there was no regional climatic shift of the magnitude of the late Wisconsin. It is surmised here that if a cold/dry climate results in saline lakes, at the extreme, then full glacio-pluvial systems must require a significant increase in precipitation along with cold paleoclimatic conditions in order to maintain deep, fresh-water lakes in the currently arid southwestern United States.

Use of environmental tracers to estimate parameters for a predevelopment-ground-water-flow model of the Middle Rio Grande Basin, New Mexico

“…This time corresponds to the last glacial maximum that occurredapproximately 21,500 years ago. Evidence for a wetter climate during this period is also present in the Estancia Basin, just east of the Sandia Mountains, in the form of playa lake deposits (Bachhuber, 1992;Alien and Anderson, 2000). Simi-larly increased recharge during this time period is suggested from 14C flow-modeling and chloride results to the west in northeastern Arizona (Zhu, 2000;Zhu and others, 2003).…”

U. S. Geological Survey Middle Rio Grande basin study: Proceedings of the Fourth annual workshop, Albuquerque, New Mexico, February 15-16, 2000

“…In addition to the steady-state model, a transient paleohydrologic model was calibrated to determine if the carbon-14 data set as a whole contained information indicating that recharge rates had changed for any time during the past 30,000 years. Paleolimnological evidence from central New Mexico has indicated that the climate in the region was wetter during the last glacial maximum (20-25 ka) (Bachhuber, 1992). The paleohydrologic calibration was set up by simulating a period of 30,000 years, with an independent value of recharge being estimated every 5,000 years.…”