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Weathering rind age assignment of Neoglacial deposits in the Okstindan Mountains, northern Norway

Mahaney W. C.

Studia Quaternaria

2016

Vol. 33, Nr 2

131--138

Previous soil stratigraphic analysis of soil morphogenesis in the Okstindan Mountains established a Late Neoglacial soil evolutionary sequence based on historically monitored and radiocarbon-dated moraine positions over the last ~3.0 cal yr BP. Thus pedon evolution ranged from C/Cu®Ah/Cox/Cu®pedostratigraphic succession of Ah/C/Cu/Lb/ Cub/Ahb/Coxb/Cub profiles with a maximum rind weathering time of ~1.0 kyr. Following successive retreat phases of Neoglacial ice, weathering rind development continued apace on moraines, each rind population recording weathering time following successive glacier stillstands. The age of the youngest deposits falls within the period 1900–1910 AD, or the last 100 yrs, with variable moraine positions all documented by historical depictions of the position of the Austre Okstindan glacial lobe prior retreating to its present position. The next older group of deposits is considered to have been emplaced near the end of the LIA or around ~1800 AD, with time of rind development set at 200 yr, possibly older. The oldest moraine set within the late Neoglacial sequence lies atop a pedostratigraphic column, the uppermost soil radiocarbon dated at ~1.0 yr BP. Given the range of mean rind development across this threshold of deposits, from 0.22 ±0.03 mm in the inner group, 0.66 ±0.07mm in the middle group, to 1.38 ±0.15 mm in the outer, older group, it is clear that finite measurements at several sites within a suite of deposits, some dated by radiocarbon, can evenly discriminate between deposits in a glacial succession.

Application of the Handysurf E-35B electronic profilometer for the study of weathering micro-relief in glacier forelands in SE Iceland

Dąbski M.

Acta Geologica Polonica

2015

Vol. 65, no. 3

389--401

This article presents the results of weathering micro-roughness measurements performed with the use of a Handysurf E-35B electronic profilometer, a new tool in geomorphological studies. Measurements were performed on glacially abraded basaltic surfaces within the Little Ice Age (LIA) glacial forelands of Hoffelsjökull, Fláajökull, Skálafellsjökull and Virkisjökull in Iceland. Results show a statistical increase in micro-roughness in a direction from the glacial termini to LIA moraines. However, a major change in the micro-roughness of basaltic surfaces only occurs during the first 80 to 100 years since the onset of subaerial weathering. Increase in rock surface micro-roughness is accompanied by an increase in weathering rind thickness and a decrease in Schmidt hammer R-values. Micro-roughness measurements with the use of the Handysurf E-35B can provide insights into initial rates of rock surface micro-relief development. The use of this instrument as a relative dating technique is limited to fine-grained rocks and decadal time-scales of weathering because of the limited range of measureable micro-relief amplitude.