• Journal of The Geomorphological Association of Korea
• /
• v.26 no.4
• /
• pp.21-31
• /
• 2019

Timing of terrace formation is a key information for understanding the evolution of fluvial systems. In particular, dating strath terrace (i.e. timing of terrace abandonment) is more difficult than depositional terrace that is conventionally constrained by radiocarbon, OSL and other dating methods targeting samples within terrace deposit. Surface exposure dating utilizing cosmogenic ¹⁰Be provides more reliability because it can be applied directly to the surface of a fluvial terrace. Thus, this method has been increasingly used for alluvial deposits. As well as other geomorphic surfaces over the last decades. Some inherent conditions, however, such as post-depositional ¹⁰Be concentration (i.e. inheritance), surface erosion rate, and density change challenge the application of cosmogenic ¹⁰Be to depositional terrace surface against simple bedrock surface. Here we present the first application of ¹⁰Be depth profile dating to a thin-gravel covered strath terrace in Korea. Monte Carlo simulation (MCS) helped us in better constraining the timing of abandonment of the strath terrace, since which its surface stochastically denuded with time, causing unexpected change of ¹⁰Be production with depth. The age of the strath terrace estimated by MCS was 109 ka, ~4% older than the one (104 ka) calculated by simple depth profile dating, which yielded the best-fit surface erosion rate of 2.1 mm/ka. Our study demonstrates that the application of ¹⁰Be depth profile dating of strath terrace using MCS is more robust and reliable because it considers post-depositional change of initial conditions such as erosion rate.

• Proceedings of the KGS Conference
• /
• 2002.05a
• /
• pp.144-147
• /
• 2002

• The Journal of the Petrological Society of Korea
• /
• v.23 no.3
• /
• pp.261-272
• /
• 2014

Over the last three decades, advances in AMS (Accelerator Mass Spectrometry) and Noble Gas Mass Spectrometer make various application of terrestrial cosmogenic nuclides (CNs) to wide range of earth surface sciences possible. Dating techniques can be divided into three sub-approaches: simple surface exposure dating, depth-profile dating, and burial dating, depending on the condition of targeted surfaces. In terms of Korean landscape view, CNs dating can be applied to fluvial and marine terrace, alluvial fan, tectonic landform (fault scarp and faulted surfaces), debris landforms such as rock fall, talus, block field and stream, lacustrine and marine wave-cut platform, cave deposits, Pliocene basin fill and archaeological sites. In addition, in terms of lithology, the previous limit to quartz-rich rocks such as granite and gneiss can be expanded to volcanic and carbonate rocks with the help of recent advances in CNs analysis in those rocks.

• The Korean Journal of Quaternary Research
• /
• v.20 no.2
• /
• pp.30-50
• /
• 2006

The long-lived radionuclide, $^{10}Be$, is produced by cosmic-ray effects in the atmosphere of the earth as well as its surface and that of other planetary surfaces and atmospheres. Accelerator mass spectrometry (AMS) was developed in late 1970s, which made $^{10}Be$ terrestrial measurements more feasible. Since then, many research applications of $^{10}Be$ for both terrestrial and extraterrestrial applications have been developed, which parallel the wide range of radiocarbon ($^{14}C$) research applications. This paper summarizes production mechanisms of $^{10}Be$ both in the atmosphere and on the surface of terrestrial and extraterrestrial environments and also provides numerous $^{10}Be$ research applications in the fields of geomorphology, oceanography, archaeology, glaciology, cosmochemistry, climatology, and planetary science. We also review some $^{10}Be$ AMS research applications.

• Journal of the Korean Geographical Society
• /
• v.38 no.3
• /
• pp.389-399
• /
• 2003

CRN (Cosmogenic radionuclide) methodology has been a versatile tool applicable to a wide range of geomorphology. This study was underiaken to ascertain the rate of erosion and exposure age of mountain-top detritus (tors and block streams) on Mt. Maneo by employing the concentrations of in-situ produced cosmogenic $^{10}$ Be and $^{26}$ Al from bedrock surfaces that are exposed to cosmic rays. The results suggest that tors on the summit were positioned here during the glacial period but no later than 65ka and block streams have been stabilized also since the last glacial period but no later than 38ka. The tors on the summit have been eroded at a slower rate (9m/Ma) than blocks on the hillslope (15m/Ma) since the initial abrupt exposure of each landform to cosmic rays, suggesting that there is a slight difference in the rate of erosion between the summit and the hillslope, and that the local relief between the two areas has been increased. When the $^{26}$ Al/$^{10}$ Be-$^{10}$ Be concentrations from samples are plotted in Lal's steady-state erosion island, one sample (from a for) has complex exposure histories, which can be explained by the occurrence of multiple chipping event of 5cm to 60cm in length on the surface of the rock.

• Journal of the Korean earth science society
• /
• v.36 no.6
• /
• pp.512-519
• /
• 2015

Although Quaternary marine terraces and onshore paleo-shoreline records provide clues to our understanding for the mode and nature of neotectonics in the Korean peninsula, it cannot be accomplished without knowledge on both independent information of the past sea level records and tectonic deformation field together with precise results of numerical dating for higher terraces. This study reported cosmogenic radionuclides ($^{10}Be$) dating results conducted in higher terraces in the eastern and western coasts of the Korean peninsula. As a result, the measured concentration ratio of $^9Be/^{10}Be$ and the exposure ages were much younger than expected. It implies that either there is possibility of error in experimental processes or the samples experienced a complex exposure history probably included a burial at some stage. Considering the past climatic conditions around the Korean peninsula and a possible complex exposure history after the emergence of marine terrace, the discovery of a suitable study area and a sampling site are an essential part of successful $^{10}Be$ dating technique.

• Economic and Environmental Geology
• /
• v.35 no.6
• /
• pp.523-532
• /
• 2002

The rare earth elements (REE) and Nd, Sr and noble gas isotopic compositions eHer'He, 4$^{\circ}$Arp6Ar) for the Quaternary alkali basaltic rocks and mantle xenoliths in the basaltic rocks from the Baegryongdo were investigated to decipher the origin of alkali basaltic magma and xenolith beneath the Sino-Korean craton. Analytical results are summarized as follows; (1) The alkali volcanic rocks with voluminous xenoliths which are represented by the Mg-olivine and clinopyroxene dominant spinel-lherzolite in the Baegryongdo consist mainly of the basalt-mugearite and basaltic andesite. (2) The REE pattern of alkali basaltic rocks characterized by high HREE is similar to that of oceanic island basalt (OlB). Relatively concordant REE patterns of the basaltic rocks suggest that the alkali basaltic magma be formed by the identical source materials. (3) The Nd-Sr isotopic data of the alkali basaltic rocks suggest that the alkali basaltic magma be originated from the depleted mantle source with a little contamination of the continental crustal materials. (4) The $^3$He/ $^4$He ratios in olivines of xenoliths ranging from 5.0${\pm}$1.lRa to 6.7${\pm}$1.3Ra are lower than that of MORB (ca. 8.0Ra). It suggest that the xenolith be derived from the subcontinental lithospheric mantle. However, the high $^3$Her'He value of 16.8${\pm}$3.IRa at 1800$^{\circ}$C fraction (sample no OL-7) might be resulted from the post-eruptive cosmogenic $^3$He. The 4OAr/ 36 Ar ratios in olivines of mantle xenoliths are comparable to that of atmospheric argon, and are much lower than that of the MORB type mantle. These facts can lead to conclusion that the olivine of the xenolith in the Baegryongdo is affected by the post-eruptive atmospheric contamination during the slow degassing process.