Glacial crushing of limestone and the production of carbonate-rich silts in a pleistocene glaciofluvial system: A potential source of loess in southern europe

This paper explores the modification of limestone bedrock and fine-grained sediment within the Pleistocene glacial and proglacial environments of the Orjen massif in western Montenegro. We have characterised the fine-grained components of till and outwash using lithological and particle size data. Two main types of fine-grained outwash sediment have been recognised and each is associated with a distinctive meltwater route. Fine-grained sediments deposited downstream of bedrock gorges (type 1 meltwater route) typically display a bimodal particle size distribution, where the carbonate silt fraction (10-60μm) has been depleted and non-carbonate silts become dominant. This probably reflects both physical sorting and corrosion of the fine-grained limestone sediment within the proglacial fluvial environment. The 10-60μm component matches the particle size characteristics of typical loess. Fine-grained outwash deposits from directly in front of the former ice margin (type 2 meltwater route) show unimodal particle size distributions which more closely resemble the grain size characteristics of the glacial till, but they also show evidence of silt depletion. We argue that the fine-grained sediment exported from glaciated limestone catchments during the cold stages of the Pleistocene formed an important source of the carbonate-rich loess in this region. © 2014 Swedish Society for Anthropology and Geography.