Application of the Schmidt-hammer for relative-age dating of glacial and periglacial landforms in the Cantabrian Mountains (NW Spain)

Abstract

A Schmidt hammer was applied for relative-age dating to 48 sites in 5 different massifs of the Cantabrian Mountains (NW Spain). The sample included glacial (moraines, erratics, and polished bedrock) and periglacial (rock glaciers, blockfields, and talus slopes) sites from the last glaciation to the present in different geomorphological contexts. The rebound (R) values agree with the morphostratigraphic reconstructions, showing progressively lower values for older deposits. Six stages from the Last Glacial Maximum to the present are inferred. The results differ according to the lithology: i) the quartzites showed higher R-values and very low weathering rates; ii) the granodiorites showed larger differences in R-values reflecting clearly age differences; iii) sandstones appear to be unsuitable for Schmidt hammer measurements in some areas; however, quartzite sandstones provide better results. The rock glaciers formed in different periods after deglaciation (i.e. just after the Last Glacial Maximum, Bölling/Allerød, Holocene), indicate a paraglacial dependence rather than climate-driven landforms. The sampled blockfields stabilized after the (almost) total deglaciation of the cirques, but their origin and significance in this mountainous area remain poorly understood.