High-Resolution Lacustrine Stratigraphy: Application to Hydrologic-Climatic Reconstruction in Southwestern United States

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Laminations of gypsum sand and silt, eolian and lacustrine clay, and organic-rich material occur on a scale of millimeters in late Pleistocene/Holocene lake sediments in the Estancia Basin in central New Mexico. A feasibility study has established the seasonal character of the laminae and their potential for reconstructing a high-resolution chronostratigraphy. The vertical and lateral continuity of the laminations provides a basis for reconstructing a stratigraphic sequence on a decimeter scale and a time-series with a temporal resolution ranging from decimeter decades to centuries. Changes in the proportion of eolian, lacustrine, and biogenic components reflect changes in water depth and volume, wind intensity, and in the hydrologic balance of the closed lake system. Reconstruction of a high-resolution stratigraphy will eventually permit the measurement of the hydrologic response to climatic forcing and quantitative estimates of changes in climatic variables. Methods applied elsewhere to the reconstruction of varve time- series will be adapted to reconstruct a time-series based on accumulated thickness and composition of bedding and laminations. These parameters will be measured in closely spaced samples, indexed to an age model for the reconstructed time-series, and expressed as sediment flux. The radiocarbon chronostratigraphy will be refined with additional analyses. The high-resolution stratigraphy in the central area of the basin will be correlated with shoreline deposits to connect the stratigraphic record to an improved hydrologic/climatic model for the Estancia Basin. In addition, the investigation will compile a record of eolian influx and will help develop methodologies for reconstructing high- resolution stratigraphic records in other lacustrine basins.