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 10Be exposure dating. Frost shattering from the backing cliff produced the boulders since the beginning of the last glacial period (~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.

The age and paleoclimate implications of relict periglacial block deposits on the New England Tablelands, Australia

“…While the other sites are not as well developed, they all display similar characteristics. Morphologically, the deposits are blockstreams similar to those described elsewhere in the world (e.g., Boelhouwers et al, 2002;Seong and Kim, 2003;Firpo et al, 2006;Gutiérrez and Gutiérrez, 2014;Oliva et al, 2016;Rhee et al, 2017) and to those that have been described and mapped from sites in the Australian Alps and Tasmania (Caine, 1983;Barrows et al, 2004).…”

“…The mode of formation of blockstreams is a controversial topic (Wilson, 2013). Harris (2016) suggested two main major modes of formation: (1) dynamic blockstreams promoted primarily by interstitial ice and snow that transport blocks downslope (Rhee et al, 2017), and (2) lag blockstreams that are associated with a pre-existing deep weathering profile being washed out by meltwater under periglacial conditions (Davies, 1958; Caine, 1983; Harris, 2016). Relict blockstreams attributable to both the dynamic and lag modes of formation have been documented in Australia.…”

“…A major issue with dating blockstreams is that there are limited targets for radiocarbon and luminescence dating and the environment is challenging for the use of surface exposure dating using cosmogenic nuclides (Barrows et al, 2004). Pilot dating studies have been carried out in Korea (Seong and Kim, 2003; Wilson et al, 2008; Rhee et al, 2017), North America (e.g., Cremeens et al, 2005), and using a Schmidt Hammer in Norway (Wilson et al, 2017). In Australia, there has been some research on the distribution and climatic significance of periglacial block deposits (e.g., Caine, 1983; Colhoun, 2002; Slee and Shulmeister 2015), but, like elsewhere in the world, age control is limited.…”

Tectonic geomorphology and Quaternary fault slip rates in the Tsambagarav Massif, Mongolian Altai

“…Skylines were measured at 10° intervals to correct for the shielding effect caused by the surrounding terrain at each topographic surface. Samples were processed at the Geochronology Laboratory of Korea University, Seoul, South Korea, following the community standard method (Kohl & Nishiizumi, 1992; Rhee et al, 2017). The processed samples were measured for 10 Be/ 9 Be using an accelerator mass spectrometer (AMS) at the Ion Beam Mass Analysis Laboratory, Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul, South Korea.…”

Granite Landform Diversity and Dynamics Underpin Geoheritage Values of Seoraksan Mountains, Republic of Korea

“…No evident cirques occur and none of the major valleys shows clear morphological features of glacial erosion (U-shaped cross-section, ice-molded hills). However, similar to some other Korean mountains (e.g., Rhee et al 2017), a clear testament of cold-climate conditions is provided by extensive blockfields (products of in situ mechanical breakdown, with little subsequent movement) and blockslopes (some gravitydriven movement may have occurred) (Park 2000(Park , 2003. Their occurrence is lithology-controlled.…”