METEORIC 10Be, FED, AND CLAY IN CRITICAL ZONE SOILS, FRONT RANGE, COLORADO

The geochemistry of soils provides useful insight into soil character and development, and when applied to steep, active hillslopes, aids in the analysis of evolving topography. Iron and clay accumulate in soil columns through time due to pedogenic processes and potential dust influx. After its deposition on the Earth’s surface by rain or dust, meteoric ¹⁰Be is similarly incorporated into a soil column. The addition of meteoric ¹⁰Be to soil analysis, combined with well-constrained delivery rates, allows for the dating of evolving soils and calculation of downslope soil transport. Here, we present a geochemical analysis of soils within the Boulder Creek Critical Zone Observatory in the Front Range, Colorado, specifically focusing on iron (Fe_d), clay content, and meteoric ¹⁰Be. Meteoric ¹⁰Be analysis shows that soils in this region are late Pleistocene to Holocene in age. Concentrations of meteoric ¹⁰Be, Fe_d, and clay in the Gordon Gulch catchment are all lower on south-facing hillslopes compared to north-facing hillslopes, indicating younger ages and faster erosion. Depth concentrations of meteoric ¹⁰Be to Fe_d show little correlation but a moderate-strong correlation between meteoric ¹⁰Be and clay, confirming previous studies that show that meteoric ¹⁰Be more readily absorbs onto clay minerals. Comparison of total inventories of the three parameters analyzed here will further the understanding of Gordon Gulch soils and more broadly, hillslope evolution.