The Development of Limestone Weathering Rind in a Proglacial Environment of the Hallstatter Glacier

The contemporary retreat of glaciers results in the development of glacial forelands which constitute excellent areas for studies on the initial stages of weathering. This research concentrates on weathering rinds developed on glacially abraded Dachstein limestone surfaces (Eastern Alps) liberated from glacial ice since LIA (mid-19th century). We performed measurements of rock surface micro-roughness and strength (Schmidt hammer), spectral reflectance, and petrographic and microbiological analyses in SEM. There was a time-dependent increase in micro-roughness, decrease in rock strength and decrease in spectral reflectivity, but only within visual light. Rock surfaces on older sites reflected infrared radiation significantly better than younger ones. SEM analysis revealed that angular micro-structures inherited from glacial abrasion dominated in younger sites, eventually giving way to more rounded micro-structures. The structure of rock (micrite versus spar, phlogopite veinlets, etc.) plays a significant role. On older sites, microorganisms were detected within the studied weathering rinds, which probably results in better infrared reflectivity. We advocate the potential role of microorganisms (mainly heterotrophic) in the dissolution of limestone, and the role of cyanobacteria in the formation of the secondary porous limestone layer (extracellular biomineralization).

Automated summary

This study focuses on the development of glacial forelands as a result of the contemporary retreat of glaciers, providing excellent areas for studying the initial stages of weathering. The research examines weathering rinds on glacially abraded Dachstein limestone surfaces in the Eastern Alps. Results show a time-dependent increase in micro-roughness, decrease in rock strength, and decrease in spectral reflectivity within visual light. Older sites reflect infrared radiation significantly better than younger ones. The study also suggests the potential role of microorganisms in limestone dissolution and the formation of secondary porous limestone layers.