摘要
金坪子堆积体位于金沙江河谷之中,处在"康滇地轴"的中部,类似一个大滑坡体。通过对金坪子堆积体的数字高程模型(DEM)、12个钻孔、1个平硐和1个竖井资料的分析,以及实地调查,对金坪子堆积体的沉积物进行沉积学、年代学和岩石地层学等多学科的研究。金坪子堆积体由12层不同的沉积物和8个地貌单位组成,其中1～9层为古金沙江河流相冲积物和坡积物、崩积物相混杂的堆积物,其堆积时间为197～137 kaB.P.;10～12层则为泥石流相堆积物;8个地貌单元由金沙江下切形成。金沙江金坪子段在中更新世末期就已形成深切的高山峡谷地貌景观,已到达现今的高度。晚更新世以来处在剥蚀抬升的均衡阶段,金坪子堆积体的发育过程主要受到构造和气候变化的影响。197～137 kaB.P.气候以冷干为主,堆积体形成了Unite2、4、6和8等四个钙质胶结层;Unite3、5、7和9的沉积特征,反映了金坪子堆积体堆积时期共和运动对其具有一定的影响。137～114 kaB.P.为冷干向暖湿转变时期,河流下切能力减弱,形成金坪子处的高水位。114～78 kaB.P.,气候转暖期,降水增多,金沙江金坪子处快速深切;unit11c中泥石流堆积黏土含量高达40%。78～41 ka.B.P.,气候冷干形成阶地下部的蚀余堆积,40～30 kaB.P.的大洪水造成河流下切形成阶地。41～0 kaB.P.为金沙江金坪子段继续深切阶段。
The diamicton of Jinpingzi,which looks like a slide according to morphological character,lies on the Kangdian tectonic zone.It is a composite diamicton that formed due to several dynamic actions at the different periods,and is a product of three geomorphic systems i.e.the ancient Jinsha river,the old Jinsha river and the modern Jinsha river,which occurred alternately. According to the DEM of the diamicton of Jinpingzi and the field investigation,there are eight geomorphic units in the diamicton of Jinpingzi,which are the upside slope,the debris flow fan,the accumulational flatform on palaeogully of Jinpingzi,the valley slide of the Jinsha river,the terrace of the Jinsha river,the beach face composed of boulders and rock masses,the meander core and the Xiaogou gully.The TL age of the terrace in the surface of the diamicton of Jinpingzi is（41.13 3.49）kaB.P.. The multidisciplinary study（sedimentology,chronology,lithostratigraphy） of the sediment of the dill of the landform suggests that the diamicton of Jinpingzi is composed of twelve stratums.The stratums form the first to the ninth are composed of colluviums,alluviums and slope wash,while the others are composed of debris flow. According to geomorphologic and sedimentologic characters of the diamicton of Jinpingzi,we can conclude that there are three geomorphologic processes,which are accumulation and sidesway（197~137 kaB.P.）,divagation and incision（137~41kaB.P.） and intensity incision（41~0 kaB.P.）.Finally the meander core formed after the deeply-incising of Jinsha river,and the cliff of the breccia formed. The Alpine Gorges has been formed during Late Medio-Pleistocene in the Jinpingzi reach of Jinsha river,and has reached the modern attitude.During Late Pleistocene,the uplift of the study area is driven by erosional unloading,the development of dicmicton in Jinpingzi has been effected by climate change.197~137 ka B.P.,which was a relatively cold-dry period,the breccias of unit 2,4,6 and 8 had formed,the sedimentary characteristics of unit 3,5,7 and 9 had form by effect of Gonghe tectonic movment.When the period changed from MIS6 to MIS5,fluvial incision dynamics descended,and higher water level had formed during 137~114 ka B.P.The Jinsha River had incised intensively during 114~78 ka B.P.because fluvial dynamics of the older Jinsha River increased under the warm-wet climate.The main body of terrace is composed of fluvial lag which had been formed in cold-dry period in 78~41 ka B.P.,the upper terrace is composed of imbricate gravels and sands which had been formed in an inundation period in 41 ka B.P.The Jinsha River has penetrated the diamicton and into the bedrock,then the meander core and the cliff opposite to the diamicton have formed since 41 ka B.P.
出处
《沉积学报》
CAS
CSCD
北大核心
2011年第5期935-945,共11页
Acta Sedimentologica Sinica
基金
高等学校博士学科点专项科研基金项目(编号:20060284028)资助
