Dating Slope Deposits and Estimating Rates of Rock Wall Retreat in Northwest Spitsbergen by Lichenometry

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Abstract
A first attempt at applying lichenometry to a geomorphological study of slopes on Spitsbergen is presented. Use of this method reveals evidence for the influence of the “Little Ice Age” (the 70 B.P. and probably 500–300 B.P. stages) on construction of debris cones and rockfall talus. Rock glaciers originated during an earlier Neoglacial period (most likely 3500–2000 B.P.). Lichenometry connected with estimates of rock debris volumes calculated according to Rapp's method allow tentative evaluations of the rates of late Holocene rock wall retreat amounting to 0.0 to 0.7 mm/yr. The main factors governing rates of retreat are the pattern of glacial dynamics and secondarily the rock type and the joint spacing. However, because there are insufficient control points to establish a growth curve for Rhizocarpon geographicum s.l. in Svalbard, chronological control is rather crude presently. Nevertheless, these results are significant in so far as they cross-check estimates proposed by Rapp utilizing other methods in central Spitsbergen and northern Scandinavia.