摘要
本文利用宇宙成因核素^26Al/^10Be埋藏测年法对宁夏沙坡头地区黄河左岸的T5、T6、T8和T9阶地开展了年代学研究。采用简单快速埋藏模式获得4级阶地的^26Al/^10Be埋藏年龄分别约为0.25Ma、0.36Ma、0.59Ma和1.06Ma，如果考虑后期剥蚀作用的影响（E≈5m/Ma），则4级阶地的年龄分别约为0.42Ma、0.39Ma、1.02Ma和1.59Ma。本研究未发现砾石大小与^10Be、^26Al核素浓度及^26Al/^10Be比值有明显相关性。
Xiangshan-Tianjingshan Fault is one of the most active neotectonic structures in the northeastern margin of Tibetan Plateau.Yellow River across this fault from west to east in Shapotou area, Ningxia Province, and formed nine terraces on the uplifted wall around Yemingshan Hill.Since these river terraces have sensitive responses to the tectonic activities, the ages of terraces could reflect the multiple phrases of the activities of Xiangshan-Tianjingshan Fault.However, chronological study of these terraces is rather difficult because the depositions of the higher ones are mainly composed by gravels.Cosmogenic nuclides ^26Al/^10Be burial dating could be applied not only on fine grain sediments but also on boulders and bedrocks.In this work, we carried out chronological study on four gravel terraces（T5, T6, T8 and T9）on the left bank of Yellow River with ^26Al/^10Be burial dating method.We first apply the simple burial model to calculate the minimum burial ages of four terraces, and obtained ca.0.25Ma（T5）, 0.36Ma（T6）, 0.59Ma（T8）and 1.06Ma（T9）, respectively.Due to the inadequate burial depth for preventing the penetration of cosmic rays, we need to take the cosmogenic nuclides post-burial production into consideration.According to the recent published local erosion rate of 5m/Ma（Ma et al., 2016）, we obtained the corrected ages of four terraces are ca.0.42Ma（T5）, 0.39Ma（T6）, 1.02Ma（T8）and 1.59Ma（T9）, respectively.These results are systematically older than the terrace ages derived from the dating of carbonate coatings on the terrace boulders.Since the carbonate coating growth could be affected by the environmental changes and the surface erosion process, and this will cause the age underestimation because of the hiatus or gaps of coatings, ^26Al/^10Be burial ages in this study probably more close to the true ages.
出处
《第四纪研究》
CAS
CSCD
北大核心
2016年第5期1216-1223,共8页
Quaternary Sciences
基金
国家自然科学基金项目（批准号：41302139）和中国地震局地质研究所中央级公益性科研院所基本科研业务专项项目（批准号：IGCEA1517）共同资助
关键词
宇宙成因核素
^26Al/^10Be埋藏测年
砾石
黄河阶地
沙坡头
cosmogenic nuclides, ^26Al/^10Be burial dating, gravel, Yellow River terrace, Shapotou,Xiangshan-Tianjingshan Fault
