Weathering of adjacent carbonate surfaces with different exposure ages – example of Kornat Island rockslide, Croatia

Morphometry of karren features developed on two adjacent carbonate surfaces with different exposure times was compared. One of the surfaces was exposed after a rockslide that occurred ~2400 years ago (as determined by cosmogenic 36Cl analyses), whereas the other was exposed to weathering for a longer time period. Karst morphologies on both surfaces were measured and results show that the surface affected by the slide has less grikes with majority inherited from previous weathering stage indicating that exposure time since the rockslide event has not been sufficient to homogenize these features between both rock surfaces. Tritkarren and rillenkarren preferentially found on the rockslide surface indicate that their genesis is likely to occur at decadal to centennial timescale. It is impossible to distinguish the size parameters of kamenitzas and solution pits found on both rock surfaces. Due to clear correlation between area and depth parameters of these forms we define a morphometric index: A/D ratio as the slope between these two parameters within each population. After an initial stage, preferential weathering occurs along the vertical axis in solution pits and laterally in kamenitzas. Therefore, we suggest that the A/D ratio is related to the evolution/relative age of the karren features. Thus, under rock surfaces affected by the same weathering conditions, lower A/D ratios of solution pits and higher A/D ratios of kamenitzas indicate longer time exposed to weathering. Although solution pits and kamenitzas are likely to be developed in decadal to centennial timescales, their morphology changes through time at millennial timescale and it can be tracked by morphometric analysis.