地质学报2025，Vol.99Issue(12)：4038-4052,15.DOI:10.19762/j.cnki.dizhixuebao.2024293
龙门山前中段绵竹地区印支期不整合面时空分布特征
Spatial and temporal distribution characteristics of Indosinian unconformity in Mianzhu area in the piedmont zone of Middle Longmen Mountains
摘要
Abstract
The Longmen Mountains,with their complex geological structure and evolution,have been a focal point of research.The middle segment of the Longmen Mountains,characterized by significant topographic gradients and complex magmatic metamorphism,has become one of the ideal areas to reveal their geological structure.However,a unified understanding of the multiple structural events that shaped the middle Longmen Mountains during the Indosinian period remains elusive.This study uses drilling and seismic data,combined with well-seismic correlation,to identify and classify Indosinian unconformities in the Mianzhu area,situated in the piedmont zone of the middle section of the Longmen Mountains.By analyzing the spatial distribution of unconformity intersection points,we outline the extent of various unconformity types across different periods,construct a chronostratigraphic framework for the Mianzhu area,and establish the unconformity evolution model map.The results show that there are four consecutive stratigraphic faults in the early Indosinian stage,5 Ma in the middle Indosinian stage I,5 Ma in the middle Indosinian stage II,and 28 Ma in the late Indosinian stage.Four sets of unconformities are identified in the study area,progressing from oldest to youngest:between the Leikoupo and Maantang Formations,between the Xiaotangzi Formation and Member 2 of the Xujiahe Formation,between Member 3 and Member 4 of the Xujiahe Formation,and between Member 5 of the Xujiahe and Baitianba Formations.In general,the unconformities exhibit a distinct spatial pattern,extending from NE to SW along the Indosinian ancient nappe,widening towards the NE and narrowing towards the SW.Furthermore,they transition from angular unconformities in the NW to parallel unconformities in the SE.The middle part of the Longmen Mountains is characterized by a multi-stage evolution,with progressive deformation from north to south,among which the early and late Indosinian phases are the key structural changes affecting the Longmen Mountains to the Sichuan basin.By determining the spatial and temporal distribution of Indosinian unconformities in the Mianzhu area and establishing a chronostratigraphic framework,this study provides a valuable foundation for quantitative analysis of the Indosinian tectonic belt within the Longmen Mountains.Moreover,it offers crucial insights into the sequence of tectonic activity during the Indosinian period.关键词
龙门山前/印支期/不整合面/剥蚀间断/时空分布Key words
Longmen Mountains piedmont zone/Indosinian/unconformity/denudation break/spatiotemporal distribution引用本文复制引用
ZHENG Na,HE Dengfa,GUO Tonglou,MENG Xianwu,WANG Renfu,WANG Ying,ZHANG Weikang..龙门山前中段绵竹地区印支期不整合面时空分布特征[J].地质学报,2025,99(12):4038-4052,15.基金项目
本文为国家自然科学基金重点项目(编号42330810)和国家自然科学基金企业创新发展联合基金项目(编号U19B6003-01)联合资助的成果. （编号42330810）
