Bouldery slope landforms on Mt. Biseul, Korea, and implications for paleoclimate and slope evolution

Abstract

Identification of bouldery landforms in mountains and correctly understanding their formative processes play an important role in reconstructing the geomorphic history of a region. We propose that blocks were liberated by frost cracking and wedging of cliff walls during the last glacial period. However, we further suggest and test four hypotheses comprising different scenarios for preconditioning by chemical weathering and subsequent block transport using terrain analysis, characterization of boulders, and Be-10 exposure dating. Frost shattering from the backing cliff produced the boulders since the beginning of the last glacial period (similar to 80 ka), and gelifluction transported them downslope throughout the last glacial period. Their activity then entered a dormant phase at the beginning of the Holocene. Distribution patterns of exposure ages of tors and block streams are similar to those of previous studies, implying that bouldery landscapes in the southern Korean Peninsula were likely to be formed by similar processes under periglacial conditions. The timing of active periods in transport of block streams corresponds well with the cold periods identified in regional and global climate proxy records. Interestingly, the activity of block streams in the study area reached a maximum during Marine Oxygen Isotope Stage 3 to 2 when the growth rate of nearby speleothems was lowest.