Schmidt Hammer exposure dating (SHED): Establishment and implications for the retreat of the last British Ice Sheet

Abstract

Ninety-eight surfaces related to the retreat of the British Ice Sheet (BIS) and dated using Terrestrial Cosmogenic Nuclide Dating (TCND) were sampled using the Schmidt Hammer to expand on relative dating techniques and establish Schmidt Hammer exposure dating (SHED) as an effective method for dating glacial landforms in the UK. The BIS is an effective analogue for contemporary glacial systems but our understanding of its retreat under changing climate conditions is constrained by a limited number of dates obtained from existing methods (14C, OSL). These methods are restricted in their application to glacial environments and while TCND has addressed this to some degree, its cost and potential for outliers encourage the establishment of new techniques. SHED fulfils this requirement by providing a cost-efficient method for obtaining numerous direct ages that are of comparable accuracy and precision to TCND. A multi-lithology approach has established that many rock types are unsuitable for numerical dating. However, a robust calibration curve was generated (R2 = 0.81, p = textless 0.01) for granite surfaces and applied to 31 undated granite erratics on Shap Fell, NW England. SHED indicates that BIS retreat occurred at 16.5 ± 0.5 ka, a conclusion which supports our current understanding of regional deglaciation and indicates that SHED can be a valuable and cost-effective geochronological tool.

Publication
Quaternary Geochronology