한반도 해안-하안단구 퇴적층에 대한 K 장석 pIR-IRSL연대측정법 적용가능성 고찰 = 울진 하안단구와 구산단층 연대측정

국문 초록 (Abstract)

이 논문에서는 K-장석 pIR-IRSL<SUB>290</SUB> 연대측정법의 한반도 해안-하안단구 퇴적층의 연대측정 적용가능성을 알아보기 위하여, 다양한 환경(해성, 하성, 풍성)에서 형성된 한반도 해안-하안단구 시료들의 K-장석 pIRIRSL<SUB>290</SUB>, IRSL<SUB>50</SUB>, 석영 OSL 신호특성을 살펴보고, 경북 울진군 노음리 하안단구 퇴적층과 구산단층 퇴적물에 대한 연대측정을 실시하였다. 연구에 사용된 27개의 시료들에 대한 K-장석 pIR-IRSL290 신호의 2D<SUB>0 </SUB>값은 평균적으로 약 700 Gy로, IRSL<SUB>50 </SUB>신호의 2D<SUB>0 </SUB>값과 유사하였으며, 석영 OSL 신호의 2D<SUB>0</SUB> 값(약 250 Gy) 보다는 3배 정도 높았다. 일부 시료에 대한 K-장석 pIR-IRSL<SUB>290</SUB>, IRSL<SUB>50</SUB>, 석영 OSL 연대측정 결과, K-장석 pIRIRSL<SUB>290</SUB> 연대는, IRSL<SUB>50 </SUB>및 석영 OSL 연대보다 상당히 높았다. 이는 퇴적과정동안 장시간 햇빛에 노출되어도 제거되지 않는(unbleachable) pIR-IRSL<SUB>290</SUB> 신호에서 기인했을 가능성이 있다. 경북 울진군 노음리의 하안단구 퇴적층과 구산단층 퇴적층에서 분리한 K-장석 pIR-IRSL<SUB>290</SUB> 신호와 석영 OSL 신호도 모두 방사선포화상태에 있어, 정확한 퇴적연대를 측정하는데 한계가 있었다. 하지만, 각 신호의 성장곡선으로부터 얻은 2D<SUB>0 </SUB>값은 노음리 하안단구 퇴적층은 109-140 ka 이전, 구산단층에 의해 절단된 퇴적층은 적어도 100-105 ka 이전에 형성되었을 가능성을 강력히 시사한다. 이 결과는, 기존 ~40-50 ka의 석영 OSL 신호를 기반으로 한 구산단층 퇴적층의 연대가 방사선포화현상에 의해 과소평가된 연대임을 의미한다.

다국어 초록 (Multilingual Abstract)

In this paper, in order to test the possibility of applying K feldspar pIR-IRSL<SUB>290</SUB> signal(read out at 290℃) to date old terrace sediments(up to ~ 200 ka, MIS 7) in Korea, we investigated luminescence properties of pIR-IRSL<SUB>290</SUB> signals in K feldspar extracts from 27 marine and fluvial terrace sediment samples, and these were compared with those of quartz OSL and conventional K feldspar IRSL<SUB>50</SUB> (readout at 50℃) signals. The averaged 2D<SUB>0</SUB> value of K feldspar pIR-IRSL<SUB>290</SUB> growth curves was ~ 700 Gy, which is consistent with that of IRSL<SUB>50 </SUB>signal, and this is 3 times higher than that for quartz OSL (~ 250 Gy) on average. Where possible, K feldspar pIR-IRSL<SUB>290</SUB> ages were compared with quartz OSL and conventional IRSL<SUB>50</SUB> ages. Our preliminary K feldspar pIR-IRSL<SUB>290</SUB> ages were older than quartz OSL ages by about 200%, while fading rate-corrected conventional IRSL<SUB>50</SUB> ages are in good agreement with those based on quartz OSL. This seems to indicate the possibility of K-feldspar pIR-IRSL<SUB>290</SUB> age overestimation due to the presence of unbleachable pIR-IRSL<SUB>290</SUB> signals, even with a prolonged exposure to sunlight. Both quartz OSL and K-feldspar pIR-IRSL<SUB>290</SUB> signals for the samples from Noeum fluvial terrace and Gusan fault site were all in dose saturation level, thus unable to estimate the formation ages of the sediments. However, 2D<SUB>0</SUB> values derived from the dose response growth curves strongly indicate that the Noeum fluvial terrace sediments have formed before 109-140 ka, while the fluvial sediments from Gusan fault were desposited before 100-105 ka. Further, this seems to suggest that the previous quartz OSL ages of ~40-50 ka for Gusan fault sediments should be the underestimated ones due to dose saturation problem.

목차 (Table of Contents)

• 요약
• Abstract
• 서론
• 시료 및 실험방법
• pIR-IRSL₂₉₀ 연대측정법의 한반도 해안-하안단구 퇴적층에의 적용가능성
• K-장석 pIR-IRSL₂₉₀과 석영 OSL 신호의 I/I₀비: pIR-IRSL₂₉₀ 연대측정법의 한반도 해안-하안단구 퇴적층에의 적용가능성
• K-장석 pIR-IRSL₂₉₀ 연대측정법을 이용한 경북 울진 노음리 하안단구퇴적층과 구산단층에 대한 연대측정
• 결론
• References

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