河套盆地西缘山前低台地沉积特征对“吉兰泰-河套”古湖消退过程及其控制因素的指示意义  

The sediment features of lower piedmont platforms along Western Hetao Basin and implication for subsiding process and controlling factors of "Jilantai-Hetao" Megalake

作　　者：公王斌[1] 胡健民[1] 李振宏[1] 吴素娟[1] 刘洋[2] 阎纪元[3] 

机构地区：[1]中国地质科学院地质力学研究所国土资源部古地磁与古构造重建重点实验室,北京100081 [2]昆明理工大学,云南昆明650093 [3]山东科技大学,山东青岛266510

出　　处：《地学前缘》2013年第4期190-198,共9页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(1212011120099,1212011120100)

摘　　要：河套盆地西缘与北缘发育一系列山前台地,台地沉积物记录了盆地环境变化。高台地沉积物记录了"吉兰泰—河套"古大湖形成过程,而低台地记录了古大湖的消退过程。盆地东部与西部低台地沉积特征不同,东部低台地由全新世冲洪积物组成,西部狼山山前低台地由晚更新世晚期—全新世(14 C年龄(15 260±60)a cal BP与(9 810±40)a cal BP)湖相沉积组成。低台地沉积特征及测年结果表明,1.5万年至1.0万年前后,河套盆地东部湖泊消失,而西部仍发育湖泊,古湖经历了自东向西的退却过程。古湖消退受盆地周缘断裂活动的差异性控制,1.5万年至1.0万年前后,盆地周缘断裂活动性总体上东强西弱,东部大青山山前断裂活动速率较高,大量碎屑物质进入盆地,呼和坳陷湖泊萎缩甚至消失,西部狼山山前断裂活动速率较低,进入盆地碎屑物质较少,临河坳陷大部分地区发育湖泊。There are a series of piedmont platforms along west and north margins of the Hetao Basin.The sediment of the platforms recorded the environment changes of the basin.The sediment of higher platforms recorded the formation of ＂Jilantai-Hetao＂ megalake,whereas the sediment of lower platforms recorded the subsiding process of the megalake.Sediment features in the lower piedmont platforms in east and west parts of the basin are different.In the east part,the lower platforms consisted of Holocene alluvial sediments,whereas in the west part the lower platforms consisted of lacustrine sediments,in which we obtained two 14C ages,15260±60 cal BP and 9810±40 cal BP,respectively.Depositional features and dating of the lower platform indicate that,from the late Late Pleistocene to the Early Holocene,the margin of the Hohhot depression was covered by alluvial fans,and the Linhe depression was occupied by a lake,indicating that the megalake subsided from east to west.The subsiding process as controlled by different activities of the marginal faults.Since 15 ka,in the east part of the Hetao Basin,the Daqingshan Piedmont Fault was more active,and lots of clastics were transported into Hohhot depression,leading to shrinkage or disappearence of the lake.In the west part of the Hetao Basin,the Langshan Piedmont Fault was less active,only a few clastic sediments were deposited into the Linhe depression,and thus it was covered by the lake.

关 键 词：河套盆地 山前台地 晚更新世晚期—全新世早期 湖相沉积 活动断裂 

分 类 号：P619.2[天文地球—矿床学] TE254.3[天文地球—地质学]