2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 18
Presentation Time: 8:00 AM-4:45 PM

The Be-10 Signals from the near Surface Samples of the Masanri Marine Terrace, Pohang, Korea

KIM, Kyeong Ja, EUM, Chul Hun, KIM, Ju Yong and LEE, Youn Soo, Korea Institute of Geoscience and Mineral Resources, 92 Gwhang-no, Yuseong-gu, Daejeon, 305-350, South Korea, kjkim@kigam.re.kr

Recently, we investigated both in-situ produced and atmospheric Be-10 concentrations of the layers of aeolian sand deposit and a neighboring bedrock sample of a marine terrace located in Masanri, Pohang in the southern part of Korea. Below about 3 meters of the aeolian sand deposit, uneven volcanic bedrock layer is located. The concentrations of in-situ produced Be-10 of the sand samples do not decrease as depth increase. This implies the sand samples have inherited Be-10 before the recent surface exposure event on the current marine terrace location. On the other hand, the atmospheric Be-10 concentrations for the raised weathered bedrock soil and a depth profile of the sand deposit ranged from (6.67±0.007)x10^7 and (1.47±0.01)x10^8. Maejima et al, 2005[1] claimed that age estimation of a raised marine terrace is feasible by knowing Be-10 deposition rate in soil and the Be-10 concentrations associated with clay development in raised marine terrace. This sampling location of Masanri marine terrace was claimed to be a site where a paleomagnetic excursion (the Blake Event) has been observed[2] in Korea. The depth profile of atmospheric Be-10 concentrations of this study shows a maximum Be-10 concentration appeared at the depth between 200 and 250 cm. If the sand deposit of Masanri site is associated with the lowest paleomagetic intensity as the evidence of the Blake Event, the expected Be-10 concentration at the relevant depth should be a maximum. Consequently, application of soil dating as the method[1] is rather difficult for this site. The results of Be-10 of this study provide the first new reference data set of Be-10 in a marine terrace of Korea. This presentation will discuss details of the Be-10 data on marine terrace of Korea.

References: [1] Y. Maejima et al. Geoderma 126, 389-399 (2005). [2] T. M. Shim, PhD Thesis, Yeonsei University, Korea [2006].