Meteoric 10Be in Lake Cores as a Measure of Climatic and Erosional Change

Abstract:

Utilization of meteoric ¹⁰Be as a paleoenvironmental proxy has the potential to offer new insights into paleoprecipitation records and paleoclimate models, as well as to long-term variations in erosion with climate. The delivery of meteoric ¹⁰Be to the surface varies with precipitation and its strong adsorption to sediment has already proven useful in studies of erosion. Thus, it is likely meteoric ¹⁰Be concentrations in lake sediments vary under both changing climate and changing sediment influx. Assessment of the relative importance of these changes requires the comparison of ¹⁰Be concentrations in well-dated lake cores with independent paleoenvironmental proxies, including oxygen isotope, pollen, and charcoal records, as well as variation in geochemical composition of the sediments. Blacktail Pond details 15,000 years of climatic change in the Yellowstone region. We develop a new model framework for predicting meteoric ¹⁰Be concentrations with depth in the core, based on sedimentation rates of both lake-derived and terrigenous sediments and changes in the flux of meteoric ¹⁰Be with precipitation. Titanium concentrations and previously determined ¹⁰Be concentrations in wind-derived loess provide proxies for changing delivery of ¹⁰Be to the lake by terrigenous sources. We use existing paleoenvironmental data obtained from this core and the surrounding region to develop models for changing rainfall across the region and predict meteoric ¹⁰Be delivery to the lake by precipitation. Based on a suite of ~10 models, sedimentation rate is the primary control of meteoric ¹⁰Be in the Blacktail Pond core unless terrestrial input is very high, as it was post-glacial in the early Holocene when the lake experienced a high influx of loess and terrigenous sediments. We used these models to inform sample selection for ¹⁰Be analysis along the Blacktail pond core. Core sediments are processed for meteoric ¹⁰Be analysis using sequential digestions and standard extraction procedures. ¹⁰Be concentrations will be used to test the suite of model predictions, and validate the application of meteoric ¹⁰Be concentrations as a proxy for changing erosion and precipitation.