西昌盆地新基姑地区大箐组风暴岩特征及其地质意义  

Characteristics and Geological Significance of Tempestites in the Daqing Formation,Xinjigu Area,Xichang Basin

作　　者：金鑫[1] 宋金民[1] 刘树根[1,2] 孙玮 丁一[1] 邓双林[1] 许智雄 徐宏远 李立基 李章畅 郎悦竹 冯梦媛 谢国梁 JIN Xin;SONG JinMin;LIU ShuGen;SUN Wei;DING Yi;DENG ShuangLin;XU ZhiXiong;XU HongYuan;LI LiJi;LI ZhangChang;LANG YueZhu;FENG MengYuan;XIE GuoLiang(State Key Laboratory of Oil and Gas Reservoir Geology and Exploration,Chengdu University of Technology,Chengdu 610059,China;Xihua University,Chengdu 610039,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室(成都理工大学),成都610059 [2]西华大学,成都610039

出　　处：《沉积学报》2021年第4期908-918,共11页Acta Sedimentologica Sinica

基　　金：国家自然科学基金(41872150);四川省科技厅重点研发项目(2018JZ0078)。

摘　　要：西昌盆地新基姑地区奥陶系大箐组发育典型的风暴岩。风暴沉积构造主要有底冲刷构造、砾屑层理、粒序层理和丘状交错层理等。通过剖面实测,识别出3种风暴沉积序列:序列Ⅰ主要为薄层泥晶白云岩夹黄灰色极薄层状泥岩,为风暴浪基面以下的远源风暴浊流沉积,为风暴岩序列的E1段沉积,主要发育于外缓坡下部;序列Ⅱ发育底冲刷面(A)、平行层理段(C)、丘状交错层理段(D),主要发育于外缓坡上部;序列Ⅲ主要由底冲刷面和砾屑段(A)、粒序段(B)组成,主要沉积于中缓坡相带。风暴段自下而上表现为由序列Ⅰ向序列Ⅲ过度,并且沉积环境由外缓坡下部、外缓坡上部向中缓坡演化,形成一个在纵向上水深变浅的沉积特征。风暴岩的发育表明西昌盆地在奥陶纪大箐期处于低纬度地区。西昌盆地大箐组在新基姑以东地区处于中—外缓坡地带,而在新基姑以西地区为内缓坡地带,因而认为大箐组在新基姑以西的方向具备发育大规模优质颗粒滩型储层的古地理背景。Tempestite deposits are found in the Ordovician Daqing Formation,Xinjigu area,Xichang Basin.Major stormsediment indicators include scouringfill structures,stormgenerated gravelstones and hummocky crossstratifications(HCS),etc.Three types of storm depositional sequences were developed:Type I is mostly composed of thinlayered muddy dolomite with yellowgrey and extremely thin layers of mudstone;this is a distal storm deposit below the storm wave base,located in the E1 section of the tempestite sequence in the deep ramp.Type II sequence consists of a storm gravelstone member(A),a parallel lamination member(C)and an HCS(D),which is deposited at the highest part of the slope near the fineweather wave base in the deep ramp.Type III sequence comprises a storm gravelstone member(A)and a graded member(B)in the middle ramp.The sequences transition from Type I to Type III(bottom to top of the storm segment),and the sedimentary environment of the storm sequence from bottom to top has evolved from the lower part to the upper part of the deep ramp,and from the deep ramp to the middle ramp,in a process of shallowing upwards.The discovery of the tempestites provides a basis for the paleogeography and palaeoplate evolution of the study area,indicating that the Upper Yangtze Block was located at low latitudes in the Ordovician.Integrated with the regional geological background,it is speculated that the Ordovician Daqing Formation is dominated on the western margin of the Yangtze Platform by midtoouter ramp facies east of Xinjigu,and by innerramp facies to the west.This implies many geological possibilities for highquality shoal reservoirs in the Ordovician Daqing Formation in the Xichang Basin to the west of Xinjigu.

关 键 词：西昌盆地 大箐组 风暴岩 沉积模式 地质意义 

分 类 号：P588.2[天文地球—岩石学]