岷江上游坡断型裂点迁移速率与构造隆升历史研究  

Study on the migration rate of the slope-break knickpoints and the tectonic uplift history in the Minjiang River

作　　者：田述军[1] 温宇航 伍文洽 李凯 TIAN Shujun;WEN Yuhang;WU Wenqia;LI Kai(School of Civil Engineering and Architecture,Southwest University of Science and Technology,Mianyang 621010,China)

机构地区：[1]西南科技大学土木工程与建筑学院,四川绵阳621010

出　　处：《地学前缘》2024年第4期314-325,共12页Earth Science Frontiers

基　　金：国家自然科学基金项目(41971214,41401195)。

摘　　要：基岩河道中坡断型裂点是构造活动和水力侵蚀共同作用的产物,根据其空间分布特征可以反演区域构造隆升历史和地貌演化过程。本文采用坡度-面积分析法和积分分析法识别出岷江上游坡断型裂点和裂点带,并结合河道纵剖面反演岷江上游的隆生历史和河口裂点形成时间,对坡断型裂点溯源迁移过程和速率进行模拟。研究结果表明:(1)岷江上游流域坡断型裂点有较明显的分层特征,干流及支流当前形成了海拔1300、2500和3500 m的3条裂点带,其对应的河道信息说明岷江上游流域早更新世以来经历了3次较为强烈的构造运动;(2)构造隆升历史大致可分为4个时期,分别为缓慢隆升(20~12 Ma)、加速隆升(12~8 Ma)、稳定隆升(8~2 Ma)和强烈隆升(2 Ma以来),其中在2.0 Ma以来,岷江上游流域的隆升速率达到0.6 mm/a;(3)3500 m裂点带对应的坡段型裂点水平迁移平均速率为38.0~127.9 km/Ma,其最小残差平方和最优拟合度均表明1.3 Ma是裂点最可能产生的时间,其溯源迁移速率为79.1 km/Ma。The regional tectonic uplift history and landscape evolution can be simulated based on the spatial distribution characteristics of slope-break knickpoints in bedrock channels,which result from the combined action of tectonic activity and water erosion.This study identifies slope-break knickpoints and knickpoint belts in the upper reaches of the Minjiang River using slope-area analysis and integral analysis methods.It then simulates the uplift history,formation times of river mouth knickpoints,and headwater migration processes and rates of slope-break knickpoints,combined with longitudinal river profiles.The findings are as follows:(1)In the upper reaches of the Minjiang River,slope-break knickpoints exhibit distinct layered distribution characteristics,forming three knickpoint belts at 1300 m,2500 m,and 3500 m in the main channel and tributaries.Data from these knickpoint belts suggest that the area has experienced three relatively intense tectonic movements since the Early Pleistocene.(2)The tectonic uplift history in this region can be divided into four periods:slow uplift(2012 million years ago),accelerated uplift(128 million years ago),stable uplift(82 million years ago),and intense uplift(since 2 million years ago),with an uplift rate of 0.6 mm/a since 2 million years ago.(3)The average horizontal migration rate of the 3500 m slope-break knickpoint ranges from 38.0 to 127.9 km/Ma,likely forming around 1.3 million years ago with a migration rate of 79.1 km/Ma according to the minimum residual squares method and optimal fitting method.

关 键 词：裂点 河道纵剖面 构造历史反演 裂点迁移 

分 类 号：P548[天文地球—构造地质学]