Abstract
AbstractThis article presents the results of weathering micro-roughness measurements performed with the use of a Handy-surf 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.
Highlights
Upon deglaciation a rock surface undergoes subaerial weathering and the resulting relief can sometimes be used as an indicator of the relative age of landforms (Hubbard and Glasser 2005)
The values of roughness parameters seem to stabilize on basaltic surfaces older than 80 to 100 years, and in the Skálafellsjökull foreland, a reverse pattern can be observed within the older sites (Text-fig. 6)
The results of this study indicate that the profilometer can provide interesting insights into the initial rates of rock surface micro-relief development and be used as a relative dating technique, but only in a decadal time-scale from the onset of subaerial weathering, given the used setting of the instrument
Summary
Upon deglaciation a rock surface undergoes subaerial weathering and the resulting relief (or micro-relief) can sometimes be used as an indicator of the relative age of landforms (Hubbard and Glasser 2005). Rather than single elements of weathering micro-relief, was performed by McCarroll (1992) and McCarroll and Nesje (1996) working on gneiss in the Storbreen marginal zone and Oldedalen in Norway. They used a micro-meter and a profile gauge, capable of measuring a micro-relief amplitude of a few millimetres and detected significant differences in rock surface roughness between landforms created in the Little Ice Age (LIA) and those from the onset of the Holocene. In the International System of Units (SI), the prefix “micro” denotes a factor of 10-6 (μm), the amplitude of rock surface relief at an order of dozens of micrometers is called “micro-roughness” in this paper
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