DUST AS A PROXY FOR LAND DISTURBANCE AND CLIMATE CHANGE IN THE SOUTHWEST

Using varves and isotopic analysis, we investigated a 142 cm sedimentary core from Columbine Lake, Colorado, spanning ~3000 years. Varves are seasonal layers containing dust sediments <1mm. We developed a chronology of dust mass accumulation rates (DMAR) based on varve couplet thicknesses, constrained by radiocarbon ¹⁴C, and radionuclides ¹³⁷Cs and ²¹⁰Pb isotopic analyses. A Bayesian statistical ensemble yielded a DMAR record (n=900). Results show a significant positive DMAR excursion around 1650 CE. This excursion indicates increased erosion from upwind sources, likely due to Spanish colonization (1598 CE) and associated livestock grazing degrading landscapes. Correlation of this record with regional Palmer Drought Severity Index data, coupling to drought does not occur until the mid-19th century. Flooding triggered by higher snowmelt and higher rainfall events exacerbated 20th century DMAR via erosion. Our study demonstrates dust as a robust proxy for reconstructing land disturbance histories and climate impacts in the Southwest. It also underscores the importance of conservation efforts to mitigate dust sources.