First 36Cl cosmogenic moraine geochronology of the Dinaric mountain karst: Velez and Crvanj Mountains of Bosnia and Herzegovina

This article presents the first attempt to date moraines in the Dinaric mountain karst using cosmogenic Cl-36 surface exposure dating technique. Twenty samples were collected from moraine boulders from two sets of the lowest and largest lateral moraines on the Velez (1965 m asl) and Crvanj mountains (1920 m asl) in Bosnia and Herzegovina. The dated lateral-terminal moraine complexes, spanning elevations from similar to 980 to 1350 m asl, are up to 2.7 km long and rise more than 100 m above the valley floor. The moraine boulders yielded Cl-36 ages spanning from Oldest Dryas for Velez (14.9 +/- 1.1 ka) to Younger Dryas for Crvanj (11.9 +/- 0.9 ka), considering the average age of the two oldest samples from each lateral moraine as the most representative time of moraine emplacement. The dated moraines mark the largest extent of glaciers in both study areas, which have been reconstructed to similar to 28 km(2) for Velez and similar to 24 km(2) for Crvanj, having a mean equilibrium line altitude at 1388 m and 1541 m, respectively. Under modern precipitation values, which account for similar to 2000 mm, the temperature depression between 8 and 10 degrees C is required to sustain the palaeoglaciers with reconstructed equilibrium line altitudes. Glaciers of similar size with such low equilibrium line altitudes during the Lateglacial have not been reported until now for the Balkan Peninsula. It is very likely that the boulder ages reflect complex exhumation and denudation histories, which at this point do not allow obtaining more precise moraine chronologies for the study areas. Nevertheless, this article delivers new data on the extent and timing of Quaternary glaciations in the Mediterranean mountains, where records of glacier fluctuations seem to be asynchronous amongst different areas. It is clear that dating moraines with cosmogenic Cl-36 surface exposure dating in carbonate lithologies in areas of high precipitation like the Dinaric karst, remains challenging. (C) 2019 Elsevier Ltd. All rights reserved.