南盘江-红水河(中段)的河流地貌特征与地壳变形

珠江作为亚洲的一条重要河流,它的中上游南盘江-红水河(中段)流经右江-南盘江被动陆缘造山带的西北段。研究南盘江-红水河(中段)的河流地貌是了解老造山带内部新构造活动情况和考察青藏高原新生代构造活动远程效应的重要手段。经过调查发现,南盘江-红水河(中段)所属的亚流域Ⅱ出现左右岸流域严重不对称,亚流域Ⅱ南部隆林至天峨一线出现近东西向弧形分水岭。隆林附近的坝索至纳贡一带,南盘江河道出现裂点段落,小流域(RN3)出现"反S"形河网,且其北边界发生地貌跃迁。该河段附近的北东向和近东西向弧形断层发育,并有弧形支流出现。天峨附近红水河河道有反向裂点出现,天峨附近的布柳河呈北东向弧形展布。文章引入了向形构造体系和旋块构造体系对上述地貌现象和构造活动特征进行解释。研究表明,南盘江-红水河(中段)的流域不对称、近东西向的弧形分水岭分布、北东向和近东西向弧形断层以及弧形支流展布受控于先存构造形成的向形构造系统。在先存的向形构造系统中,隆林一带河流的裂点、地貌跃迁和"反S"形河网等河流地貌现象是对后期构造体系活动的响应,后期构造活动继承了早期向形构造体系的格局,以祥播块体(A)为旋转中心,带动了周边构造变形,形成旋块构造体系。天峨反向裂点是上下游水利条件差异与构造抬升共同作用的结果。但旋块构造体系活动的启动和分期活动的时代仍未有合理的时间约束。亚洲大陆逃逸为旋块构造体系活动提供了一种可能的动力学解释。

FEATURES OF FLUVIAL LANDFORM AND CRUST DEFORMATIONS ALONG THE NANPANJIANG RIVER-HONGSHUIHE RIVER(MIDDLE SEGMENT)

In the geological evolution of Asias Cenozoie Era,the tectonic evolution of Tibetan Plateau not only generates lots of direct and long-ranged effects but also controls the evolution of many Asian rivers.As an important river in Asia,the Pearl Rivers upper-middle stream,which lies in the Nanpanjiang River-Hongshuihe River basin,is flowing through the northwest section of Youjiang River-Nanpanjiang Rivers Passive Margin Belt.The researches of its fluvial landforms are not only a means to comprehend the neo-tectonic movements of the old orogenic belts but also to investigate the long-ranged effects of Tibetan Plateaus activities in the Cenozoie Era.After investigations of subbasin Ⅱ,it appears seriously basin asymmetry between the left and the right banks.The near-EW arc drainage divide appears in the south of subbasin Ⅱ from Longlin to Tian'e.Both the knick-point section and the reversed-S-type river network in RN3 emerge in Nanpanjiang River channel along Longlin area from Basuo to Nagong.Landform transition can also be seen in the northern boundary of the reversed-S-shape river network.Both the growth of the NE fault,near-EW arc fault and arc tributary emerge in Longlin area from Basuo to Nagong.There are reversed-knick-point in the channel of Hongshuihe River near Tian'e.It appears the NE-arc-spread in Buliuhe River near Tian'e.In this paper,we introduce the concepts of Synformal Tectonic System and the Rotation Block Tectonic System(RBTS)to explain the landforms and the tectonic movements.The researches show that the asymmetric subbasin,the EW arc drainage divide,the NE fault,the near-EW arc fault and arc tributary spread are all controlled by the pre-existed Synformal Tectonic System.The fluvial landforms of knick-point,landform transition,reversed-S-type river network along Longlin area are the responses to the succeeding tectonic system activities.The succeeding tectonic activities are inherited from the Synformal Tectonic System.As the rotation centre,the Xiangbo block(A)deforms the tectonic in the surrounding to form the RBTS.The reversed-knick-point in Tian'e is not only resulted by the different hydraulic conditions of the upstream and downstream but also by the tectonic uplift.But there are still no geochronology constraints for the start-up time and segment activities of the RBTS.The extrusion of Asian continent provides a possible mechanical explanation for the activities of the RBTS.