A Cosmogenic Nuclide-Based Approach to Determining Amounts and Timing of Soil Erosion on Parent Materials of Known Age

The total cosmogenic nuclide inventory of an uneroded soil on a parent material of independently known age, such as a dated glacial moraine or an alluvial deposit, must correspond to the total inventory expected in a deposit with that duration of exposure to cosmic radiation.  A vertical profile through the soil and the underlying ‘parent material' enables the determination of the total cosmogenic nuclide inventory (including the quantification of any inherited cosmogenic nuclide component).  Any shortfall between the measured total inventory and the total inventory expected for the age of the parent material indicates loss of the soil and/or parent material by erosion.  Vertical profiles of two cosmogenic nuclides of substantially different half-lives and production rates, such as ¹⁰Be and ¹⁴C, should indicate the timing of any erosion that is identified, with a broad resolution to, for example, Middle or Late Holocene.  If the technique proves successful, it will provide for the first time a means of measuring and broadly dating Holocene at-a-site soil erosion, complementing techniques that rely on basin sedimentation to assess catchment-wide average soil erosion based on sediment flux to receiving basins.

We are assessing these principles using the soil formed on the Younger Dryas Loch Lomond Readvance moraine near Glasgow.  ¹⁰Be determinations on vein quartz in erratics on the moraine surface confirm the Younger Dryas age of the moraine.  In this paper we will report cosmogenic nuclide data from samples from soil pits to 2.5m depth on the crest and flank of the moraine.