【作者】 李蔚伟；

【导师】 彭向东；

【作者基本信息】 吉林大学 ， 古生物学与地层学， 2009， 硕士

【摘要】 乌拉嘎断陷盆地基底为元古界变质岩系和海西、印支期花岗岩,盆地充填沉积盖层为中、新生界,填充序列自下而上为下白垩统宁远村组、淘淇河组,上白垩统嘉荫群(永安村组、太平林场组、渔亮子组),渐新统至上新统孙吴组。乌拉嘎盆地主要充填地层为白垩系。本次矿调工作厘定了上白垩统太平林场组在乌拉嘎断陷盆地广泛发育,并通过对太平林场组叶肢介和孢粉化石组合研究与对比,确定太平林场组的时代为晚白垩世土伦期—坎潘期,这对于研究区内白垩纪地层格架的建立和断陷盆地演化规律的研究以及油气勘探均具有重要意义。通过对乌拉嘎断陷盆地的中新生代地层层序、地层接触关系以及构造变形等研究,识别厘定出2个角度不整合界面,分别是:①上白垩统嘉荫群与下白垩统之间角度不整合;②上白垩统嘉荫群与新近系孙吴组之间微角度不整合接触。造就了乌拉嘎断陷盆地表现为具有3期叠合盆地演化的特征。进而恢复了乌拉嘎断陷盆地中、新生代的构造演化历史,将其划分为3个演化阶段,即:①早白垩世的大陆裂谷断陷盆地演化阶段;②晚白垩世的大型内陆坳陷盆地演化阶段;③新近纪内陆山间盆地演化阶段。更多还原

【Abstract】 There has been a large disagreement on the division and correlation of Mesozoic and Cenozoic stratigraphic succession in Wulaga fault depression basin, which as South-eastern branch fault of Sunwu-Jiayin basin,Whether there exists Jiayin group of upper Cretaceous, there has not been reported about it at the outcrop stratigraphy before.Jiayin group can’t be found in Wulaga fault at 1:200000 geological survey (1979),only a suite of black shale were discovered in the vicinity of beacon towers,owing to no information of fossil, they correlated this sets of stratigraphic for Wuyun group Paleogene (Tertiary old) at that time,at 1991 when the Wulaga town residents excavated sand,they excavated dinosaur fossils accidentally,which identified as a typical fossil assemblage of Yuliangzi Formation,late Cretaceous at Jiayin region,Heilongjiang province,in the view of above,ZhouHaibin et (2006)determined the Sunwu formation extensive within fault of Neogene which originally delineated by 1:200000 to Yuliangzi formation of upper Cretaceous,however,as a result of failure to identify the micro-angle unconformity between Yuliangzi formation and Sunwu formation, this led to the surface spatial distribution of Yuliangzi formation expanding in Wulaga fault.The basement of Wulaga fault basin are Paleozoic metamorphic rocks and Hercynian,Indosinian granites, sedimentary cover mainly are Mesozoic and Cenozoic Sequence,the filled strata sequence from bottom to up are lower Cretaceous,which include Ningyuancun Formation,Taoqihe Formation,Fuminhe Formation,Upper Cretaceous Jiayin Group(Yongancun Formation,Taipinglinchang Formation,Yuliangzi Formation) and Sunwu Formation of Oligocene to Pliocene.Based on a solid work of geological survey of the field, Jiayin group was paid to special attention in this paper.We collected a large number of Estheria fossils in black shale,oil shale at abandoned mining pit of the original gold brick field, south mountain of Wulaga,identified them as chain fossil of China northern Estheria (Halysestheria qinggangensis band)at late Cretaceous. In view of above, it was confirmed that Jiayin group is developing and distrubuting widely in Wulaga fault depression,the formation angularly unconformited above the lower Cretaceous series.This has important significance to establishing the strata framework of Crataceous at research area and studying on the law of basin evolution.Preliminary achievements of this paper are as following:1.By studying and determining the rock association of every formation unit,fossils and depositional environment systematically, I study on comparing it to other fault depressions of Sunwu-Jiayin and Songliao basin,then establish the sequence framework of Cretaceous in fault basin.2.Through comprehensive studying on biostratigraphy,estheria,sporopollen assemblages, we determine the age of Taipinglinchang Formation and the direct evidence of its development in Wulaga Fault Basin, descripte the estherias as 3 genus 5species,this lays basis for establishing regional stratigraphic framework.3.Through field measuring of volcanic rocks,then identify the evolution of volcano-magmatic incident of the early Cretaceous, the volcanic eruption event in region at early of early Cretaceous,it was multi-phase and multi-cycle eruption, combined with isotopic age data, we determined the period and characterister of volcanic activity;4.Through field geological survey in detail,we found that after hypabyssal porphyry intrusion events,a strong uplift denudation event occurred in the region,caused the contact angular unconformity between Taipinglinchang Formation of upper Cretaceous and Taoqihe,Ningyuanchun Formation,granite porphyry of lower Cretaceous and Heilongjiang Group;Identify the strata deformation characteristics of early Cretaceous, Accordingly to this,there exist a southeast-northwest structure extruded event at late of early Cretaceous in the region;5.Based on systematically summarizes regional stratigraphy,geotectonic and magmatic petrology, through researching on stratigraphic sequence of Mesozoic and Cenozoic, contactions between stratigraphy and tectonic deformation,We can identify 2 angle unconformity interfaces at Wulaga fault depression basin,there respectively are:①Jiayin group of lower Crataceous series unconformable contact with Upper Crataceous series②Jiayin group of lower Crataceous series unconformable contact with Neogene series.So there were 3 stages superposition evolution character of basin,then analayzed tectonic evolution history of Meso-Cenozoic of Wulaga Basin,then divided into 3 periods, respectively for:①Continental rift fault basin evolution stage of early Crataceous②Large inland depression basin evolution stage of late Crataceous③Inland intermontane basin evolution stage of Neogene.更多还原