Decadal to millennial-scale solar forcing of Last Glacial Maximum climate in the Estancia Basin of central New Mexico

Abstract

Lacustrine sediments from the Estancia Basin of central New Mexico reveal decadal to millennial oscillations in the volume of Lake Estancia during Last Glacial Maximum (LGM) time. LGM sediments consist of authigenic carbonates, detrital clastics delivered to the lake in stream flow pulses, and evaporites that precipitated in mudflats exposed during lake lowstands and were subsequently blown into the lake. Variations in sediment mineralogy thus reflect changes in hydrologic balance and were quantified using Rietveld analysis of X-ray diffraction traces. Radiocarbon dates on ostracode valve calcite allowed the construction of mineralogical time series for the interval ~23,600 to ~18,300ka, which were subjected to spectral analysis using REDFIT (Schulz and Mudelsee, 2002). Dominant periods of ~900, ~375, and ~265yr are similar to cycles in Holocene 14C production reported for a variety of tree ring records, suggesting that the Lake Estancia sediments record variations in solar activity during LGM time. A prominent spectral peak with a period of ~88yr appears to reflect the solar Gleissberg cycle and may help, along with the ~265yrcycle, to explain an ongoing mystery about how Lake Estancia was able to undergo abrupt expansions without overflowing its drainage basin.