Rock hardness as a relative-age indicator of glacially striated surfaces on Marion Island

Abstract

Rock hardness is an accepted measure for the degree of weathering of a rock surface. Over time, gradual exposure to the elements causes disintegration of the rock surface, weakening the rock to produce lower values of rock hardness. For decades the Schmidt hammer has been the preferred instrument to obtain rock hardness values, but the Equotip, manufactured by the same company, has, in recent years, been used in an increasing number of relative-age dating studies. Due to its light weight, internal electronic memory and ability to correct for certain errors, the Equotip is considered superior to the Schmidt hammer by some geomorphologists, but is still not used nearly as often as the Schmidt hammer. On Marion Island, the deglaciation timeline is not well established, and an improved knowledge of this will have implications on the interpretation of the island’s landscape development since the Last Glacial Maximum (i.e. 10-30 kya.. Assuming rock weathering is reset by a glacial period, rock hardness can serve as a relative-age indicator of striated surfaces and shed light on the rate of geomorphic change and ecological succession, for example. In this study, Equotip rock hardness values, collected in 2017,are presented as a relative age indicator of previously glaciated surfaces. These new values are compared to research findings and Schmidt hammer values collected by geomorphologists in the last 20 years. Further, comments are made in the light of expected age of sampled surfaces and new directions are suggested for future studies using the Equotip for rock hardness measurements. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.