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

Tomkins, Matt D.; Dortch, Jason M.; Hughes, Philip D.

doi:10.1016/j.quageo.2016.02.002

Cited by 43 publications

(50 citation statements)

References 131 publications

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“…Fortunately, the Mournes are considered to have experienced a similar glacial history to the sites sampled by Tomkins et al . ().…”

Section: Methodsmentioning

confidence: 85%

“…Recently, Tomkins et al . () produced a series of R‐value calibration curves by sampling 76 surfaces in the UK, dated using 10 Be terrestrial cosmogenic nuclide dating (TCND). Tomkins et al .…”

Section: Methodsmentioning

confidence: 97%

“…Tomkins et al . () produced individual curves for different lithologies, but found that granite surfaces alone demonstrate a statistically significant relationship between exposure age and R‐values (Fig. ).…”

Section: Methodsmentioning

confidence: 97%

“…This returned an average R‐value of 48.70 ± 1.3, compared to the calibration value of 48.08 ± 0.82 reported by Tomkins et al . (), and values were corrected to account for this difference.…”

Section: Methodsmentioning

confidence: 97%

“…This indicated a 2‐point difference in R‐values between the beginning (6 May 2016) and end of sampling (23 July 2016). By arranging the R‐values chronologically, based on the date/time of collection, a correction was made assuming a linear deterioration in Schmidt hammer performance (following Tomkins et al ., ). To utilize Tomkins et al .…”

Section: Methodsmentioning

confidence: 99%

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Younger Dryas glaciers and climate in the Mourne Mountains, Northern Ireland

Barr

Roberson

Flood

et al. 2017

J Quaternary Science

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Here, we present evidence to suggest that the Mourne Mountains, Northern Ireland, were last occupied by glaciers during the Younger Dryas Stadial. The margins of these glaciers are marked by moraines, chronologically constrained to the Younger Dryas by Schmidt hammer exposure dating. Reconstructions indicate that these glaciers had equilibrium‐line altitudes (ELAs) ranging from 356 ± 33 m (a.s.l.) to 570 ± 9 m (a.s.l.), with a mean of 475 ± 36 m (a.s.l.). ELAs rise from west to east, probably reflecting the contribution of windblown snow and ice to the accumulation of Younger Dryas glaciers in the western Mournes. Taking this into consideration, a mean ‘climatic’ ELA of 529 ± 4 m (a.s.l.) is calculated for the mountains as a whole. Assuming a mean annual sea level air temperature of −8 °C, and an annual temperature range of 34 °C, degree‐day modelling suggests that during the Younger Dryas, accumulation at the ‘climatic’ ELA of glaciers in the Mournes was 846–990 mm a−1. This suggests increased aridity, relative to present, and is consistent with other parts of NW Europe, where reduced precipitation alongside notable cooling is thought to reflect increased North Atlantic sea ice extent during the Younger Dryas.

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“…Fortunately, the Mournes are considered to have experienced a similar glacial history to the sites sampled by Tomkins et al . ().…”

Section: Methodsmentioning

confidence: 85%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

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Younger Dryas glaciers and climate in the Mourne Mountains, Northern Ireland

Barr

Roberson

Flood

et al. 2017

J Quaternary Science

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Quantifying the effects of carborundum rock surface smoothing for Schmidt hammer R‐value metrics measured on glacial erratics in the North American Great Lakes region

Shepherd,

Portenga,

Peplinski

2024

Earth Surf Processes Landf

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Schmidt hammer R‐values, which reflect the degree of rock surface weathering, can be paired with independent rock surface exposure ages to produce Schmidt hammer exposure‐age dating (SHD) calibration curves that are used to provide rapid estimations of exposure ages for undated rock surfaces. In this Letter, we lay the groundwork for later establishing a SHD calibration curve based on glacial erratics deposited by the Laurentide Ice Sheet in the North American Great Lakes region. First, we establish a reference R‐value for a calibration boulder, which may be used to facilitate direct comparison of R‐values collected by different individuals using mechanical N‐type Schmidt hammers, specifically. We then assess how no, light or heavy use of a carborundum puck to smooth rock surfaces affects resulting R‐value data. Lastly, we compare two different R‐value metrics on the same rock surface: Rmean (n = 30) versus ΔR (Rmax − Rmin of five consecutive R‐values on the same spot). In all assessments, Rmean is similar for erratic surfaces with no and light surface treatment, and both are significantly lower than Rmean of surfaces with heavy treatment. Thus, we advise against the use of heavy surface treatment in SHD applications. We observe no relationship between inferred erratic age and either Rmean or ΔR, which could arise from inferred ages of erratics being inaccurate, from inferred ages of erratics being too similar or from measuring too few erratics from each landform.

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Timing of glacial retreat in the Wicklow Mountains, Ireland, conditioned by glacier size and topography

Tomkins

Dortch

Hughes

et al. 2018

J Quaternary Science

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Reconstructing the deglacial history of palaeo-glaciers provides vital information on retreat processes, information which can inform predictions of the future behaviour of many of the world's glaciers. On this basis, this paper presents 170 Schmidt Hammer exposure ages from moraine boulders and glacially sculpted bedrock to reveal the post-Last Glacial Maximum (LGM) history of the Wicklow Mountains, Ireland. These data suggest that large ice masses survived for 4-7 ka after retreat of the Irish Sea Ice Stream and were sustained by summit ice fields until $16.6 ka. Post-LGM retreat was driven by climate and involved numerous short-term ice front oscillations ( 1 ka), with widespread moraine deposition during Heinrich Stadial 1. In contrast, marked asynchroneity in the timing of Younger Dryas deglaciation is closely linked to snow redistribution which demonstrates the sensitivity of small cirque glaciers ( 1 km 2 ) to local topography. This result has important implications for palaeoclimate reconstructions as cirque glacier dynamics may be (at least partly) decoupled from climate. This is further complicated by post-depositional processes which can result in moraine ages (e.g. 10 Be) which post-date retreat. Future palaeoclimate studies should prioritize cirques where snow-contributing areas are small and where postdepositional disturbance of moraines is limited. Ã Area within the glacier drainage basin within the 210-300˚quadrant þ all other slopes which overlook the glacier (gradients >25˚).

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

Cited by 43 publications

References 131 publications

Younger Dryas glaciers and climate in the Mourne Mountains, Northern Ireland

Younger Dryas glaciers and climate in the Mourne Mountains, Northern Ireland

Quantifying the effects of carborundum rock surface smoothing for Schmidt hammer R‐value metrics measured on glacial erratics in the North American Great Lakes region

Timing of glacial retreat in the Wicklow Mountains, Ireland, conditioned by glacier size and topography

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