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K-Ar Age-dating Results of Some Major Faults in the Gyeongsang Basin: Spatio-temporal Variability of Fault Activations during the Cenozoic Era
경상분지 내 주요단층의 K-Ar 연대: 신생대 단층활동의 시·공간적 특성
Econ. Environ. Geol. 2019 Oct;52(5):449-57
Published online October 31, 2019;  https://doi.org/10.9719/EEG.2019.52.5.449
Copyright © 2019 the Korean society of economic and environmental gelology.

Song Yungoo1*, Sim Ho1, Hong Seongsik1 and Son Moon2
송윤구1* · 심호1 · 홍성식1 · 손문2

1Yonsei University
2Pusan National University
1연세대학교, 2부산대학교
Received October 27, 2019; Revised October 27, 2019; Accepted October 27, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
We present the K-Ar age-dating results of the bulk and the less than 0.1 μm fraction of the fault gouges collected from some major faults in the Gyeongsang basin. We try to determine the timings of fault activation based on the mineralogical characteristics, and to interpret the spatio-temporal variability of the major fault events during the Cenozoic Era by considering together with the previous results. We propose at least the 3-times of major fault events at about 50 Ma, and just after 30 Ma and 20 Ma in the Gyeongsang basin, which were inferred from the combined approach of the K-Ar ages and the clay mineralogy of the bulk fault gouges and the <0.1 µm fractions. The fault activation timings of the Yangsan fault tend to be younger in the northern part than in the southern part. In particular, the inferred fault events just after 30 Ma and 20 Ma are mainly detected in the Ocheon fault and the related faults, and the fault in the Gyeongju area. The fault activation timings of the major faults can be revised accurately by using illite-age-analysis(IAA) method. These geochronological determinations of the multiple events of the major faults in the Gyeongsang basin are crucial to establish the tectonic evolution in the southeastern part of the Korean Peninsula during the Cenozoic Era.
Keywords : K-Ar age, fault gouge, fault activation, illite-age-analysis(IAA), Gyeongsang basin

 

December 2019, 52 (6)