Testing Luminescence Dating on the Sediments Derived from Debris Flow: A Case Study from Lao-Nung River, Southern Taiwan.
Date Issued
2014
Date
2014
Author(s)
Chen, Ya-Lin
Abstract
In order to understand the recurrence of disastrous debris flow events, dating of the debris flow derived deposits has become an important mission. However, using radiocarbon dating can only partially accomplish this mission because of the rare and nonsystematic sample findings. Therefore, it is necessary to find another method to solve above-mentioned problems. Although luminescence dating has been widely applied on several types of deposits, the issue of incomplete bleaching is still a challenge for sediments deposited in debris flow environments. If this problem can be properly solved, luminescence dating will become a useful tool since its major material is commonly distributed quartz. In the Lao-Nung River valley there are a lot of fan terraces which were formed by debris-flow events. For the purpose of assessing luminescence dating for such kind of deposits, three sampling sites were targeted: BC01, CS01, and TY01. BC01 and CS01 are both identified as dammed-up fluvial sediments, and TY01 is sand matrix within debris flow sediments. Furthermore, for all samples radiocarbon ages as independent age control are available. To test the feasible way for equivalent dose, single-aliquot regenerative-dose (SAR) protocol has been applied to both single grain and small aliquot. Then use these two methods to examine the incomplete bleaching problem. For the dose rate estimate, combing x-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), and gamma-ray spectrometry (GRS) measurements were both carried out. Since the bleaching effect is various between different samples for such sediments, the burial ages were therefore corrected through several age models and yielded the final results close to their corresponding radiocarbon ages. The results show widely distributed equivalent doses and also a discrepancy between ICP-MS + XRF and GRS in the annual dose evaluation. In fact, the scattered equivalent dose distribution may indicate the complexity of transport and deposition histories, and the discrepancy of the annual dose may indicate an unstable environment. The luminescence dating results show good agreements with the radiocarbon dating results; hence, luminescence dating has a potential to date sediments deposited in debris flow environments. Though those characteristics related to debris flow were left questions in the traditional luminescence dating, this study gives the acceptable solution that is to combine the single-grain method plus the minimum age model (MAM) together.
Subjects
luminescence dating
debris flow
Lao-Nung River
Type
thesis
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