Subglacial carbonate deposits - a new source for studying the presence of glaciers in a glaciokarstic environment

Subglacial carbonate deposits (Fig. 1c) have been exposed on the lee sides of small protuberances on a bare polished and striated limestone bedrock surface in the immediate vicinity of the disappearing Triglav (Figs. 1a, 1b and 2) and Skuta glaciers in southeastern Alps, Slovenia. The preliminary uranium-thorium dating of those carbonates indicate that they were deposited in the Last Glacial Maximum and the Younger Dryas. Unlike other remnants of glacial deposits (e.g., moraines), subglacial carbonates are prone to fast weathering and may be eroded in a few decades, but Triglav and Skuta glaciers, have generally been viewed as relicts of the Little Ice Age with discontinuous presence due to the warm Holocene Climatic Optimum. If Triglav and Skuta glaciers melted completely during the Optimum, the Last Glacial Maximum and Younger Dryas subglacial carbonates should have not survived the weathering and denudation. But there is lack of information on subglacial carbonates in the vicinity of glaciers in southeastern Alps, and the lack of information on the exact rate of subglacial carbonate frost weathering. The question “have the glaciers survived the Holocene Climactic Optimum, and if they did, why?” can only be answered by a focused approach with high-resolution analyses of the subglacial carbonates.

The aim of the project is to establish whether glaciers in southeastern Alps in Slovenia are disappearing for the first time in Holocene, and what are the forcing components since the Holocene Climactic Optimum globally was characterised by higher temperatures than today. This will be achieved by the study of subglacial carbonate deposits in the high mountain karst environments of the southeastern Alps. We will use the modern laboratory techniques including U-Th dating of subglacial carbonates, 36Cl nuclide dating of substrate, mineralogical analysis of carbonates, geochemical analyses of carbonates and related water/ice bodies including particulates in the present ice, and frost weathering tests. The results will be put into the wider environmental context in order to determine the period when the glacierets in southeastern Alps were thick enough to cause regelation and, consequently, deposition of subglacial carbonates, and what was the glaciers behaviour throughout the Holocene in relation to palaeoclimate that favoured survival of subglacial carbonates. Finally, we will relate the results to the present rising temperatures and glacier retreat and provide the data on their future resolution.