内蒙古东部陆西凹陷中北部上侏罗统层序地层格架及体系域特征分析

SEQUENCE FRAMEWORK AND CHARACTERISTICS OF SYSTEMS TRACTS OF THE UPPER JURASSIC IN THE MIDDLE─NORTHERN LUXI DEPRESSION OF INNER MONGOLIA

对内蒙古东部开鲁盆地陆西凹陷地质和地球物理资料的综合研究表明 ,上侏罗统沉积以温湿气候条件下的粉、细砂岩及泥岩为特征 ,其沉积序列可以被划分成周期为 3— 5Ma的 5个沉积层序 ,各沉积层序之间均为不整合面或与之相关的整合面。沉积层序格架和构型主要受控于构造活动、气候和物源供给。各沉积层序的展布也受盆地结构和断裂差异活动的影响 ,表现出南厚北薄的地层展布特征。由于在马北斜坡存在地形或断裂坡折带 ,故可将一个沉积层序细分成低位、湖侵和高位体系域。在明确首次和最大湖泛面基本特征的基础上 ,重点叙述了层序B的低位、湖侵和高位体系域的近岸水下扇、扇三角洲等沉积体系特征和层序构型主控因素。对有利烃源岩、储层和盖层等成藏基本条件进行分析后 。

The Upper Jurassic of Luxi depression in Kailu Basin was deposited in humid climate, and could be divided into five sequences with 3-5 Ma cycle according to the comprehensive researches of geological and geophysical data. The boundaries among these different sequences are unconformity and its corresponding conformity. Tectonic activity, climate and material supply controlled the framework and style of a sequence. The basin palaeogeography and fault activity influenced on distributions of the Upper Jurrasic. The sequence in study area was made up of lowstand, transgressive and highstand system tracts due to topographic (faulted) break. Characteristics of the lowstand, transgressive and highstand system tracts of the sequence B are described particularly. It is pointed out that the favorable lithological traps are located mainly on nearshore subaqueous fans of fall block of Xishaogen fault and on turbidite fan under topographic break in the sequence C.