Schmidt-hammer R-values from glacially-scoured bedrock surfaces across glacier-foreland boundaries: Insights into Holocene weathering rates with implications for exposure-age dating

John A. Matthews, Richard W. Mourne, Peter Wilson, Jennifer L. Hill, Celia Robbins, Stefan Winkler

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Schmidt-hammer R-values were measured on glacially-scoured bedrock outcrops located inside and outside of 11 ‘Little Ice Age’ glacier-foreland boundaries in the Jotunheimen and Jostedalsbreen regions of southern Norway. Analysing paired samples differing in exposure age by ~10,000 years constitutes a field experiment on chemical weathering rates within and between regions. Mean R-values (± 95% confidence intervals) from inside sites were 65.9 ± 0.6 and 66.9 ± 0.6 for rock surfaces composed of pyroxene-granulite gneiss in Jotunheimen at altitudes of 990–1360 m above sea level and granite and granitic gneiss in the Jostedalsbreen region at 270–620 m a.s.l. The corresponding values from outside sites of 39.9 ± 0.9 and 39.0 ± 0.9 were significantly lower, indicating a higher degree of chemical weathering. In contrast, regional differences in mean R-values were insignificant. A similar pattern is reflected in indices of rock weathering (39.0% for Jotunheimen and 41.6% for Jostedalsbreen), and weathering rate (2.8 R-value units and 3.0 units per 1000 years, respectively). These results imply an estimated minimum age resolution of Schmidthammer exposure-age dating of ~350–625 years and a maximum age range of ~20,000 years. They suggest potential application of the Schmidt hammer to both studies of weathering rates and exposure-age dating at the regional scale, despite lithological variation associated with different rock types and climatic variation associated with altitudinal differences of up to 1000 m between the sites.
    Original languageEnglish
    Article number109139
    Pages (from-to)1-9
    Number of pages9
    JournalGeomorphology
    Volume454
    Early online date11 Mar 2024
    DOIs
    Publication statusPublished online - 11 Mar 2024

    Bibliographical note

    Publisher Copyright:
    © 2024

    Keywords

    • Schmidt hammer
    • R-values
    • Rock-surface weathering
    • Chemical weathering
    • Exposure-age dating
    • Glacier foreland
    • Field experiment
    • South Norway
    • Glacier forelands

    Fingerprint

    Dive into the research topics of 'Schmidt-hammer R-values from glacially-scoured bedrock surfaces across glacier-foreland boundaries: Insights into Holocene weathering rates with implications for exposure-age dating'. Together they form a unique fingerprint.

    Cite this