川西北地区晚三叠世卡尼期气候事件沉积的微相及环境演化

发布时间：2018-01-29 16:53

本文关键词： 川西北卡尼期气候事件沉积微相环境演化硅质海绵礁　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：晚三叠世卡尼期气候事件是三叠纪最显著的全球气候变化事件之一,在川西北绵竹汉旺、绵竹观音崖、安县雎水等地马鞍塘组中也被等时识别,主要反映了从碳酸盐岩到碎屑岩的岩性变化。在晚三叠世末期的印支运动效应下,加之晚三叠世极为动荡的古气候特征,使得川西北马鞍塘组沉积环境极为复杂,沉积相划分存在争议。本次研究的目标是厘定川西北卡尼期气候事件沉积的微相特征,探究卡尼期气候事件前后的沉积环境演化过程和规律,及其在古生物学、地球化学等方面的响应。通过野外剖面勘察、采样及室内薄片分析,古生物化石鉴定,地化测试手段,结合国内外卡尼期事件的研究资料及采取岩石沉积微相恢复古环境的方法,对卡尼期地层剖面中碳酸盐岩至陆源碎屑岩段的岩相学、古生物学、地球化学特征进行分析。发现川西北马鞍塘组沉积序列从早卡尼期的生屑—鲕粒灰岩和早卡尼期末发育的硅质海绵礁灰岩,突变为中卡尼期黑色书页状页岩,最后至晚卡尼期钙质粉砂质泥岩、钙质泥质粉砂岩。将马鞍塘组碳酸盐段划分为6个微相类型和17个次级微相微相类型,将碎屑岩段划分为5个微相类型,认为研究区晚三叠世卡尼期环境演化过程从内缓坡鲕粒—生屑滩亚相→中缓坡鲕粒-生屑滩亚相→中缓坡硅质海绵礁亚相→浅海泥亚相→滨海潮坪亚相,最后到小塘子组三角洲前缘亚相的变化。浅海泥亚相的灰黑色钙质泥页岩中生物多见,植物叶片和茎杆化石、黄铁矿丰富,显示着低能贫氧的环境又伴随着淡水输入的过程,这一明显的岩相变化与卡尼期气候事件过程中淡水和陆源碎屑物质大量输入有重要的关系。推测地层序列中碳酸盐补偿深度(CCD)上升,同时依据C、O同位素偏移以及卡尼期菊石标志性分子等特征认为研究区卡尼期事件沉积与西特提斯洋地区卡尼期气候事件具有等时对比性,马鞍塘组中部硅质海绵礁的死亡则可能受海平面升降速率、大火山岩省集中爆发、板块构造运动和季风性气候等因素的影响。这一系列地质现象与晚三叠世古气候复杂多变、海平面升降变化频繁、构造活跃有重大关系。
[Abstract]:The late Triassic Carney climate event is one of the most significant global climate change events in Triassic. It is also identified in Maantang formation of Mianzhu Hanwang, Mianzhu Guanyin Cliff, Anxian Jushui in northwestern Sichuan. It mainly reflects the lithologic changes from carbonate rocks to clastic rocks. Under the Indosinian movement effect at the end of the late Triassic and the extremely turbulent paleoclimate of the late Triassic. The sedimentary environment of Maantang formation in northwestern Sichuan is very complex and the sedimentary facies division is controversial. The purpose of this study is to determine the microfacies characteristics of the Kani climatic events in northwestern Sichuan. The evolution process of sedimentary environment and its response in paleontology and geochemistry before and after the Carney climatic events were studied. The fossil fossils were identified by field profile survey sampling and laboratory sheet analysis. Combined with the research data of Carney events at home and abroad and the method of recovering paleoenvironment by sedimentary microfacies, the lithofacies and paleontology of carbonate rock to continental clastic rock in Carney stratigraphic profile were studied. It is found that the sedimentary sequence of Maantang formation in northwestern Sichuan changed from early Carney bioclastic oolitic limestone and siliceous sponge reef limestone to middle Carney black sheet shale. Finally, calcareous silty mudstone and calcareous argillaceous siltstone are divided into 6 microfacies types and 17 secondary microfacies types, and the clastic rock member is divided into 5 microfacies types. It is considered that the environmental evolution process of the late Triassic Carney period in the study area changed from the inner gentle slope to the subfacies of the oolitic shoal. 鈫扢iddle gentle slope oolitic shoal subfacies. 鈫扢iddle gentle slope siliceous sponge reef subfacies. 鈫扴hallow-sea mud subfacies. 鈫扵he subfacies of littoral tidal flat and finally to the delta front subfacies of Xiaotangzi formation. There are many organisms in the gray black calcareous shale of the shallow-sea mud subfacies and the fossil plant leaves and stems are rich in pyrite. It shows that the environment of low energy and poor oxygen is accompanied by the process of fresh water input. This obvious lithofacies change has an important relationship with the mass input of fresh water and continental clastic materials during the Carney climatic event. The carbonate compensation depth (CCDD) in the stratigraphic sequence is estimated to be rising, and at the same time, according to C. The characteristics of O isotope migration and the signature molecules of Carney permethrin suggest that the Carney event deposition in the study area is isochronous to the Carney climatic events in the West Tethys Ocean. The death of siliceous spongy reef in the middle of Maantang formation may be affected by the rate of sea level rise and rise. This series of geological phenomena is closely related to the late Triassic paleoclimate, the frequent changes of sea level and the active tectonics.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532;P534.51

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