Collaborative Research in Holocene Geology and Anthropology: Paleoclimate, Landscape Evolution, and Human Occupation of the Western Lake Titicaca Basin, Peru

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ABSTRACTThe ultimate goal of this collaborative study is to determine how Holocene climate variability affected landscape evolution in tributary valleys of the western Lake Titicaca basin and how Holocene landscape evolution in those tributaries influenced human activities. To meet this goal we will work at the intersection of three disciplines: paleoclimatology, fluvial sedimentology, and archaeology. We will create a proxy-based, high-resolution (decadal), properly interpreted paleoclimate time series for the western Lake Titicaca basin by collecting and analyzing sediment cores from small, high-sedimentation-rate lakes. We will generate new sedimentologic and geomorphic data, from three river valleys in the same region, and use those data to create a basinwide model of fluvial evolution in the context of regional climate change and base level. And, we will generate new archaeological data that will begin to fill the gaps in our knowledge of the early prehistory (especially the record of the Archaic Period, ca. 10,000 to 3500 cal BP) of the basin. These data will address important questions about the character of the initial occupation of the basin, the dynamics of the sedentarization process, and the expansion of agropastoral settlements following sedentarization.In this study we aim to produce the best-dated and best-understood reconstruction of Holocene precipitation in tropical South America. This record is needed to answer important paleoclimate questions (such as the nature of the sea-surface temperature forcing of the tropical atmosphere), but it also essential to our ultimate research goal. Once climate variability is securely known, we can address questions concerning the evolution of fluvial landscapes within the proper climatological context. Holocene fluvialsedimentology in the western Titicaca basin is largely controlled by precipitation variability, which affects both riverine discharge and base level (the level of Lake Titicaca). Few studies of fluvial evolution have been done with the complete knowledge of the relevant records of both climate and base level, so this is an unusual opportunity to increase our understanding of both the rates and processes of sediment aggradation and downcutting, as well as possible non-linearities in the fluvial response to climate and base-level variability. Because fluvial variability is a key factor in both landscape evolution and the lives of both modern and ancient occupants of the basin, a secure knowledge of climate and landscape variability will allow us to address serious issues relating climate change and human activities. The new archaeological data we will collect will complement ongoing work elsewhere in the basin and the data, gathered within a highly resolved paleoclimatic context accompanied by a well-constrained reconstruction of natural landscape evolution, unrivaled in many other research settings, will allow us to document the relative timing of environmental and cultural change.