This study seeks to quantify the rate and timing of regolith generation in the Critical Zone at the Susquehanna Shale Hills Critical Zone Observatory (SSHO). Meteoric 10Be depth profiles were determined using
measurements from 30 hillslope soil and bedrock core samples in an effort to constrain 10Be inventories. The SSHO is located in the temperate climate zone of central Pennsylvania and comprises a first-order
watershed developed entirely on a Fe-rich, organic-poor, Silurian-aged shale. Two major perturbations to the landscape have occurred at SSHO in the geologically recent past, including significant and sustained
periglacial activity until after the retreat of the Laurentide ice sheet (21 ka) and deforestation during early colonial land-use. Bulk soil samples (n = 16) were collected at three locations along a planar
hillslope on the southern ridge of the catchment, representing the ridge top, mid-slope and valley floor. Rock chip samples (n = 14) were also collected from a 24 m deep core drilled into the northern ridge top.
All meteoric 10Be concentration profiles show a declining trend with depth, with most of the 10Be retained in the uppermost decimeters of the soil. Meteoric 10Be inventories are higher at the mid-slope
and valley floor sample sites, at 3.71 ± 0.02 1010 at/cm2 and 3.69 ± 0.02 1010 at/cm2, than at the ridge top site (1.90 ± 0.01 1010 at/cm2). The 10Be inventory at the convex ridge top site implies a minimum
residence time of 10.6 ka, or if erosion is steady, an erosion rate of 19.4 ± 0.2 m/My.
West, N., Kirby, E., Bierman, P., Rood, D., (2011): Preliminary estimates of regolith generation and mobility in the Susquehanna Shale Hills Critical Zone Observatory, Pennsylvania, using meteoric 10Be. International Symposium on the Geochemistry of the Earth’s Surface, Boulder, CO, June, 2011.
This Paper/Book acknowledges NSF CZO grant support.