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Schmidt Hammer exposure dating ( SHED )
| Content Provider | Semantic Scholar |
|---|---|
| Copyright Year | 2018 |
| Abstract | 5 Recent research has established Schmidt Hammer exposure dating (SHED) as an effective method 6 for dating glacial landforms in the UK. This paper presents new data and discussion to clarify and to 7 evaluate calibration procedures. These make a distinction between Schmidt Hammer drift following 8 use (instrument calibration), and variation between both individual Schmidt Hammers and between 9 user strategies when utilising age-calibration curves (age calibration). We show that while test anvil 10 methods are useful for verifying that Schmidt Hammers maintain their standard R-values, they are 11 inappropriate for instrument calibration except for the hardest natural rock surfaces (R-values: ≥ 12 70). A range of surfaces were tested using 3 N-Type Schmidt Hammers, which showed that existing 13 anvil calibration procedures led to consistent overestimation of R-values by up to 17.9%. In contrast, 14 new calibration procedures, which are based on the use of a calibration point which lies within the 15 range of R-values measured in the field [Dortch et al. 2016, Quat. Geochron., 35, 67-68], limit 16 variance to maximum of 4.4% for surfaces typically tested by Quaternary researchers (R-values: 25 17 60). Moreover, these new calibration procedures are more appropriate for age calibration as they 18 incorporate operator variance through choice of sampling location. New calibration procedures are 19 used to compile an updated age-calibration curve based upon 54 granite surfaces (R2 = 0.94, p < 20 0.01) from across Scotland, NW England and Ireland. The inclusion of a further 29 terrestrial 21 cosmogenic nuclide (TCN) exposure ages extends the calibration period to 0.8 – 23.8 ka, covering 22 the entire post-Last Glacial Maximum (LGM) history of the British-Irish Ice Sheet. To facilitate 23 comparison between studies, an online calculator is made available at http://shed.earth for Schmidt 24 Hammer instrument and age calibration and SHED exposure age calculation. The SHED-Earth 25 calculator provides a rapid and accessible means of exposure age calculation to encourage wider and 26 more consistent application of SHED throughout the British Isles. 27 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.research.manchester.ac.uk/portal/files/63887964/QUAGEO_Tomkins_et_al_2018_Pre_proof_copy.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
