湘东北隆起区前中生代抬升剥蚀过程的地层记录

Stratum records of Pre-Mesozoic uplift-denudation processes of northeast Hunan uplift area

湘东北地区为一主要出露新元古界冷家溪群的构造隆起带,其前中生代的抬升剥蚀过程模糊不清且尚未得到研究。本文通过新元古代的冷家溪群—上古生界地层序列、地层发育和缺失情况及其反映的不整合特征,尝试性重塑了湘东北前中生代抬升剥蚀过程,形成以下主要认识:湘东北地区自北往南可划分为临湘、岳阳、金井、长沙、醴陵等5个特征有别的抬升-剥蚀区,造成抬升-剥蚀的构造事件包括冷家溪期末的武陵运动、板溪期末的雪峰运动和早古生代后期的加里东运动,其中加里东运动包括奥陶纪末的北流运动和志留纪中后期的广西运动;武陵运动自北而南在各抬升-剥蚀区造成的抬升剥蚀量分别为>0~5200、800~6900、600~3200、500~3200、500~8000 m;雪峰运动造成的抬升剥蚀量在临湘抬升-剥蚀区不明,在岳阳抬升-剥蚀区约300~800 m,在金井抬升-剥蚀区约1800 m,在长沙和醴陵抬升-剥蚀区不明显;加里东运动自北而南在各抬升-剥蚀区造成的抬升剥蚀量分别约为500、3300~>4400、2400~7900、300~7100、3100~9300 m。上述抬升剥蚀过程为武陵、雪峰和加里东等构造运动特征提供了一定约束。

Northeast Hunan is a tectonic uplift belt with Neoproterozoic Lengjiaxi Group outcropped mainly,whose pre-Mesozoic uplift-denudation processes isn’t distinct and has not been studied.According to Lengjiaxi Group-upper paleozoic stratigraphic sequences,the conditions of stratigraphic development and deficiency,and corresponding characteristics of uncomformitis or discomformitis,the pre-Mesozoic uplift-denudation processes of northeast Hunan are reconstructed,and brought forward recognition mainly in the following.From north to south,the northeast Hunan uplift area can be divided into five pre-Mesozoic uplift-denudation areas with different features such as Linxiang,Yueyang,Jinjing,Changsha and Liling uplift-denudation area.The tectonic events related with pre-Mesozoic uplift-denudation were Wuling Movement in late Lengjiaxi Period,Xuefeng Movement in late Banxi Period and Caledonian Movement in late Early Paleozoic.The Caledonian Movement included Beiliu Movement in late Ordovician and Guangxi Movement in middle-late Silurian.From north to south,the uplift-denudation measures of the uplift-denudation areas caused by Wuling Movement were>0-5200,800-6900,600-3200,500-3200 and 500-8000 m,respectively.The uplift-denudation measure of Linxiang uplift-denudation area caused by Xuefeng Movement was not clear.Yueyang uplift-denudation area was about 300-800 m,and Jinjing uplift-denudation area was about 1800 m,Changsha and Linling uplift-denudation areas were not apparent.From north to south,the uplift-denudation measures of the uplift-denudation areas caused by Caledonian Movement were 500,3300->4400,2400-7900,300-7100 and 3100-9300 m,respectively.The uplift-denudation processes provided some constraints for Wuling Movement,Xuefeng Movement and Caledonian Movement.