Relict landslide development as inferred from speleothem deformation, tectonic data, and geoelectrics.

Abstract The direct dating of pre- and postfaulting dislocated calcite speleothems afforded new insight into slope failure in the Tatra Mountains in southern Poland. A multi-approach study of the karstic Kalacka Cave (non-crevasse type) enabled us to infer the slope deformation structure, which had been poorly preserved in ground surface topography, using combined methods including geomorphological and structural mapping of cave and ground surfaces, paleostress analysis, near-surface electrical resistivity tomography (ERT) and induced polarization methods (IP), uranium series dating (234U/230Th), calcite microtexture analysis, and stable isotope (δ18O and δ13C) analysis. Here, slope deformation began with dilation between 280 ± 7 ka and 265 ± 8 ka and proceeded as deep-seated gravitational slope deformations. The final stage consisted of dilation rejuvenation and rockfall during the latest Pleistocene or Holocene (post 35 ± 4 ka). Additionally, some dilations are evident beyond the extent of the landslide detected by ERT, indicating further progradation of slope failure. Since this failure was initiated during the climatic transition from MIS 9 to MIS 8, stable isotope analysis of calcite flowstone layers was applied to test climate factors. The correlation of calcite microtexture and δ18O and δ13C compositional changes with the interval of dilation activity indicates that regional environment factors, chiefly an increase in precipitation, probably contributed to slope destabilization. Highlights • A previously unknown relict landslide was identified. • Dilation in speleothems was directly dated. • Three phases of landslide evolution were identified. • Stable isotope analysis implied an precipitation increase as a reason for slope failure. [ABSTRACT FROM AUTHOR]