摘要
古汾河改道是运城盆地新生代时期一次重要的地表巨变过程,对于古汾河改道时限目前仍存在着中更新世和晚更新世2种观点,尚未有统一的定论。研究以运城盆地栲栳塬晚更新世沉积序列为调查对象,在光释光测年的基础上,厘定了沉积序列转换的关键时限;结合碎屑锆石U-Pb同位素测年,分析了栲栳塬晚更新世沉积序列的成因及地质主控因素。研究认为:运城盆地栲栳塬晚更新世沉积序列具有双层结构的特点,下部为一套河流相砂体,上部为一套风成相黄土,二者之间的界限大约在7.6~6.3万年;碎屑锆石年龄序列对比分析认为,栲栳塬晚更新世早期的河流相沉积与运城盆地汾河古河道的沉积特征基本一致,晚更新世中期,由于峨眉台地的区域性抬升,古汾河发生改道进而退出运城盆地,栲栳塬早期的河流相沉积之上开始接受持续的风成相沉积;运城盆地晚更新世中期的构造抬升事件在鄂尔多斯盆地周缘均有响应,预示着青藏高原在该时期存在一期明显的构造隆升,其远程效应是造成汾河改道退出运城盆地的主要动力。该研究成果从沉积角度为运城盆地古汾河的改道时限提供了新的证据。
The ancient Fen River diversion was a crucial earth's surface transformation in the Yuncheng Basin during the Cenozoic.The time frame for the diversion of the ancient Fen River is still characterized by two views:the middle Pleistocene and the late Pleistocene,which has yet to be finalized.This study investigated the late Pleistocene sedimentary sequence of the Kaolao Tableland in the Yuncheng Basin,and the critical time frame of the sedimentary sequence transition was determined based on optically stimulated luminescence(OSL)dating results.The causes of the late Pleistocene sedimentary sequence of the Kaolao Tableland and the geological factors that controlled the sequence were analyzed using detrital zircon U-Pb isotope dating.It is concluded that the late Pleistocene sedimentary sequence of the Kaolao Tableland in the Yuncheng Basin is characterized by a two-layer structure,with fluvial sands in the lower part and eolian loess in the upper part.Based on the OSL dating results,the formation time of the boundary between these two parts is between~76-63 ka B.P.Comparative analysis of detrital zircon age sequences indicates that the early Pleistocene fluvial sands in the Kaolao Tableland and sediments in the ancient Fen River have similar age sequence characteristics.Therefore,it can be deduced that the regional tectonic uplift of the northeastern Emei Terrace in the middle of the late Pleistocene resulted in the diversion and exit of the ancient Fen River from the Yuncheng Basin and the sedimentary facies began to change from fluvial to eolian.The tectonic uplift in the middle of the late Pleistocene extensively developed around the Ordos Basin,and that indicates a significant tectonic uplift of the Tibet Plateau during this time,whose remote effect might be the major cause for the exit of the ancient Fen River from the Yuncheng Basin.This research provides new sedimentary evidence for the time frame of the ancient Fen River diversion in the Yuncheng Basin.
作者
南德斌
李振宏
董晓朋
寇琳琳
韦利杰
NAN Debin;LI Zhenhong;DONG Xiaopeng;KOU Linlin;WEI Lijie(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,China)
出处
《地质力学学报》
CSCD
北大核心
2023年第4期497-511,共15页
Journal of Geomechanics
基金
中国地质调查局地质调查项目(DD20221644,DD20190018)
国家自然科学基金项目(41972119,41702216)。
关键词
河流相
风成黄土
古汾河
晚更新世
运城盆地
锆石U-PB年龄
fluvial facies
eolian loess
ancient Fen River
late Pleistocene
Yuncheng Basin
Zircon U-Pb ages
作者简介
第一作者:南德斌(2000-),男,在读硕士,从事沉积地质与大地构造方面的研究工作。E-mail:nandebin@163.com;通讯作者:李振宏(1973-),男,研究员,从事沉积地质与大地构造方面的研究工作。E-mail:lizhennhong@126.com。
