Baker 9417896 The principal objective of this project is to document and understand decade- to century-scale paleoclimatic variations in the monsoon region of northwestern India, using detailed sedimentary records from three lake in northwestern India. The finely- laminated sediments in these lakes preserve an exceptional record of high-resolution lake-level variations over the last 10,000 to 13,000 years, possibly the most complete and detailed Holocene paleoclimatic record within the Indian Monsoon region. The lakes lie in the arid/semiarid Thar Desert at the boundary of the region dominated by summer monsoon rainfall (Singh et al., 1990), and are thus particularly sensitive to fluctuations in the strength of the monsoon. Analysis of these lacustrine records will address how the decadal-scale variations in the monsoon respond to longer-term shifts in the monsoon paleoclimate, providing a high-resolution record that covers a sufficiently long time scale to fully capture the natural range of variability in the monsoon system, information that is essential for understanding near-term future climatic variations in the monsoon region. This is a collaborative project between researchers at Central Washington University and the of University of Arizona (see accompanying proposal). The methodology involves reconstructing decade- to century-scale changes in lake levels, salinity, and sediment influx in three shallow, closed-basin lakes through a combination of (1) detailed stratigraphy and sedimentology of finely laminated sediments, (2) evaporite and clay mineralogy, and (3) radiocarbon dating. Potential application of microfauna, trace elements, stable isotopes and pollen toward this problem will be explored and tested, but will not be a main focus of the study. These data, along with modern data on precipitation, water-table elevations , evaporation, and temperature, will be used to construct hydrological lake-budget models and quantify th e changes in hydrologic and climatic parameters necessary to produce the lake fluctuations. The analyses will concentrate on the high-resolution variations preserved in the primary stratigraphy during extended periods of high, low , and transitional lake-level conditions. We will emphasize specific periods of interest, including (a) internals of high variability and changing conditions, such as wet-dry transitions, (b) short-lived, shallow lakes in the late Holocene that reflect minor climatic fluctuations and/or extreme events in the last 4000 years and (c) periods of particularly high (e.g. 4000-6000 BP) or low lake levels. Analysis of the high- resolution paleohydrological variations will add a new dimension to broader-scale reconstructions of Holocene paleoclimates in monsoonal regions of India, Asia and Africa.
