粤北南雄盆地构造演化及其对红层地貌发育的影响

发布时间：2018-04-20 07:55

本文选题：南雄盆地 + 南雄断裂　；参考：《河北地质大学》2017年硕士论文

【摘要】：南雄盆地位于广东北部与江西南部的交界地带,是一处晚白垩纪以来形成的NE-SW走向的不规则条带状半地堑式的箕状断陷盆地,是粤北地区典型的拉张断陷红层盆地,南雄断裂是南雄盆地的控盆断裂。本文对南雄盆地及南雄断裂的区域地质背景、地质成因、构造-沉积演化及红层地貌发育等方面问题综合地球化学特征、地层学、年代学、地貌学等相关学科进行了详细的探讨和总结,主要取得了以下主要认识和结论:1.南雄断裂可能在早白垩世的早期(约140Ma左右)就开始了拉张作用,南雄盆地随着南雄断裂的拉张开始形成并接受沉积,随后由于区域应力场由拉张转为挤压,南雄盆地存在该时代的地层缺失。2.南雄断裂的形成是多种因素共同作用的结果,印支-燕山期形成的造山带由于重力失稳导致的拉张作用以及区域上的拉张应力场或是断裂形成的最主要原因,而燕山期的岩浆热隆规模较小,不足以为断裂的长期活动提供充足动力,因此只能是断裂形成的次要因素。3.南雄断裂的岩石学特征指示断裂运动存在韧性-脆性的转变,断裂带内的岩石具有较为明显的分带特征,自断裂下盘至上盘根据岩性大致分为构造片理化带、硅化过渡带和构造碎裂带。4.南雄盆地的基底物质组成较为复杂,不同区域的基底的岩石密度和布格重力异常特征均显示不同特征,盆地的西半盆基底岩石密度较小,由早古生代变质岩组成,东半盆基底密度较大,为结晶作用强、密度较大的花岗岩组成。5.南雄盆地的地层发育与南雄断裂的活动存在阶段性的对应关系,南雄断裂不同时期的运动在盆地内部地层中均有所体现。当南雄断裂发生快速拉张时,在盆地内部对应形成一套快速沉积的粗碎屑沉积,分选磨圆均较差,且多伴有小规模的顺层玄武岩侵入。当南雄断裂拉张运动较为稳定时,对应盆地内部形成一套粒径较细的砂岩、粉砂岩等。当南雄断裂在始新世由拉张转变为挤压时,南雄盆地就停止了沉积过程并逐渐封闭抬升,遭受剥蚀。6.南雄盆地的红层地貌发育与构造运动有着密切的联系,晚白垩世到始新世期间为红层沉积提供了必要的空间,后期构造运动和区域应力作用下形成的共轭剪节理、断面控制了盆地内红层山地、丹霞地貌的形态特征及分布,新构造运动以来的间歇式抬升造成了盆地内部4级红层台地的形成,在后期地表流水和重力崩塌的影响下形成了高低起伏的红层丘陵,但盆地内部出现的劣地式红层荒漠系人为成因。
[Abstract]:The Nanxiong basin is located in the border area between northern Guangdong and southern Jiangxi. It is an irregular banded semi-graben graben basin formed since the late Cretaceous. It is a typical extensional fault depression red bed basin in northern Guangdong. Nanxiong fault is a controlled basin fault in Nanxiong basin. In this paper, the geochemistry, stratigraphy, chronology of the Nanxiong Basin and the Nanxiong fault are discussed in terms of their regional geological background, geological origin, tectonic-sedimentary evolution and red bed geomorphology. Geomorphology and other related disciplines have been discussed and summarized in detail, and the following main understandings and conclusions have been obtained. The Nanxiong fault probably began to stretch in the early Cretaceous (about 140Ma). The Nanxiong basin formed and accepted the deposit with the extension of the Nanxiong fault, and then the regional stress field changed from tensioning to squeezing. In Nanxiong Basin, there is a stratigraphic deficiency of the age. 2. The formation of Nanxiong fault is the result of a combination of many factors, and the main reason for the extension of the Indosinian Yanshanian orogenic belt due to gravity instability and the tensile stress field in the region or the formation of the fault, The Yanshanian magmatic thermal uplift is small enough to provide sufficient power for the long-term activity of the fault, so it can only be a secondary factor of fault formation. The petrological characteristics of the Nanxiong fault indicate that the movement of the fault is ductile and brittle, and the rocks in the fault zone have obvious zonation characteristics. According to the lithology, the upper face of the self-fault downplane is roughly divided into structural sheet physical and chemical zones. Silicification transitional zone and tectonic fragmentation zone. 4. The material composition of the basement in Nanxiong Basin is quite complex. The rock density and Bouguer gravity anomaly of the basement in different regions all show different characteristics. The basement rock density of the western half basin of the basin is small and is composed of early Paleozoic metamorphic rocks. The basement density of the east half basin is high, which is composed of granites with strong crystallization and high density. The stratigraphic development of Nanxiong basin has a corresponding relationship with the activity of Nanxiong fault, and the movement of Nanxiong fault in different periods is reflected in the inner strata of the basin. During the rapid extension of Nanxiong fault, a set of rapid depositional coarse clastic deposits were formed in the basin, and the separation and grinding circles were poor, and most of them were accompanied by small scale intrusion of bedding basalt. When the extensional movement of Nanxiong fault is relatively stable, a set of fine grain size sandstone and siltstone are formed in the corresponding basin. When the Nanxiong fault changed from extension to compression in the Eocene, the Nanxiong basin stopped the sedimentary process and gradually closed and uplifted and suffered denudation. The development of red bed geomorphology in Nanxiong Basin is closely related to tectonic movement. During the period of late Cretaceous to Eocene, it provides necessary space for red bed sedimentation, and conjugate shear joints formed under the action of late tectonic movement and regional stress. The cross section controls the red bed mountains in the basin, and the morphological characteristics and distribution of the Danxia landform. The intermittent uplift since the neotectonic movement resulted in the formation of the 4 grade red bed platform in the basin. Under the influence of surface water and gravity collapse, the red beds hilly with high and low fluctuation were formed in the late stage, but the red bed desert system in the interior of the basin was formed artificially.
【学位授予单位】：河北地质大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P542

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