辽中凹陷北洼古近系东二下亚段湖底扇沉积类型及时空演化机理分析  

Sedimentary Types and Genetic Mechanism of the Space-time Evolution of Sublacustrine Fans of the Paleogene in Lower Ed2 Formation, Northern Sub-sag of the Liaozhong Sag

作　　者：刘艺萌 张藜 黄晓波 郑敬贵 徐伟 LIU YiMeng;ZHANG Li;HUANG XiaoBo;ZHENG JingGui;XU Wei(Tianjin Branch of CNOOC China Ltd.,Tianjin 300459)

机构地区：[1]中海石油(中国)有限公司天津分公司

出　　处：《沉积学报》2019年第6期1280-1295,共16页Acta Sedimentologica Sinica

基　　金：国家科技重大专项（2016ZX05024-003)~~

摘　　要：辽中凹陷北洼古近系东二下亚段发育14期湖底扇沉积。基于湖底扇类型划分,对不同类型湖底扇沉积控制因素、成因机制及不同类型湖底扇之间的时空演化规律进行了研究。结合深水重力流沉积学理论,依据湖底扇水道发育程度、重力流流体性质,将研究区湖底扇分为非水道化砂质碎屑流型湖底扇、非水道化浊流型湖底扇和水道化湖底扇3种类型。非水道化砂质碎屑流型和非水道化浊流型湖底扇无明显下切水道,其中非水道化砂质碎屑流型湖底扇整体富砂,非水道化浊流型湖底扇整体富泥。水道化湖底扇发育明显下切水道,水道中发育砂质碎屑流富砂,水道外发育浊流富泥。物源富砂性及坡折带规模共同决定湖底扇沉积类型,含砂率大于30%的富砂型物源易形成非水道化湖底扇,含砂率小于30%的富泥型物源易形成水道化湖底扇。在富砂型物源背景下,当坡折规模较大时,因搬运距离远,砂泥分异充分,沉积非水道化砂质碎屑流型和非水道化浊流型两种湖底扇;当坡折规模较小时,砂泥分异不充分,只发育非水道化砂质碎屑流型湖底扇。富砂物源滑塌为非粘性体,搬运过程中易与水融合,对底部呈片状冲刷,不易形成单一水道;富泥物源滑塌为黏性体,搬运过程中对底部冲刷集中,强度更大,易形成水道。Fourteen sublacustrine fans are located in the northern sub sag of the Liaozhong Sag in the lower Ed2 For mation.A systematic study of their sedimentary characteristics,genesis and space time evolution,combined with gravity flow sedimentation theory and the degree of development of water channels and the characteristics of the gravi ty flow fluid indicated three types of sedimentation:non channelized sandy debris flow(SDF)sublacustrine fans,non channelized turbidite current(TC)sublacustrine fans,and channelized fans.The SDF and TC fans have no evi dent channel;the SDF is rich in sand,and the TC fan is rich in mud.The sand in the channelized fan is mainly con fined to the channel,and the mud is outside the channel.The main factors that determined the formation of the differ ent fan types depends on(a)whether the source is rich in sand,and(b)the scale of the slope break belt.The non channelized fans were formed when the sand content exceeded 30%of the sand content of the channelized fans.Both SDF and TC fans were found when the scale of the slope break was relatively large and the transport distance was greatest.Only SDF fans were formed when the slope break was small.Sand rich source material(non viscous and eas ily mixed with water in slump tests)did not readily form channels.Mud rich source material(viscous and not readily mixed with water in slump tests)formed obvious channels.

关 键 词：辽中凹陷 湖底扇 沉积类型 时空演化 重力流 

分 类 号：P618.13[天文地球—矿床学]