蒙古国境内贝尔湖凹陷早白垩世沉积充填演化与同沉积断裂的响应

The Responding to Syn-Sedimentary Fault System for Sediment Filling Evolvement in the Early Cretaceous,Bel-Lake Depression of Mongolia

蒙古国境内的贝尔湖凹陷是新近发现的一个主要勘探可开发区。早白垩世垂向充填演化序列综合研究表明,南屯组早期地层的大规模同生断裂系统组合样式及其分布对断陷湖盆内沉积体系域的发育、分布起着重要的控制作用。凹陷内的充填序列和演化反映了幕式断裂作用及湖盆右旋走滑特征对盆内沉积体系演化模式起着至关重要的控制作用。长期活动的同沉积断裂配合构造的右旋走滑运动严格控制古地貌、断裂坡折及断坡带的形成与分布,从而进一步控制着湖盆内碎屑岩沉积体系发育与沉积展布模式。凹陷内部的东次凹北洼槽内的洼陷边缘断裂坡折带常常控制着粗碎屑沉积体系的沉积、沉降中心,特别是低位域近岸水下扇的发育和分布,是盆内寻找砂岩油气藏的最有利区带。同沉积断裂具有多种组合样式,包括'人'或'之'字形等多种组合的断裂系统等,造就湖盆内复杂多变的构造古地貌及断裂坡折系统,严格控制着凹陷内砂体分散体系的沉积和堆积模式。揭示同沉积断裂(坡折)带的活动和分布,再造各沉积期次构造古地貌、断坡带是进行沉积体系展布模式和砂体分布预测的关键。

Newly discovered exploration development zone locates at the Bel-Lake depression in Mongolia.Early Cretaceous vertical filling and evolvement suite research indicate that large scale of syn-sedimentary fault system mode and distribution control the sedimentary tracts of fault depression basin in the Earlier Nantun Group strata.The depression filling and evolvement suite indicate that act-fracture action and dextral strike-slip of basin play an important role in sedimentary system evolvement.Long-lasting active syn-sedimentary faults system as well as tectonic dextral strike-slip controls the forming and distribution of construction palaeogeomorphology,fracture sloping and ramp zone,thereby,which further controls coarse clastic sedimentary system development and distribution mode.The north edge fracture slope zone of east sub-depression often controls the coarse clastic sedimentary system of deposition and depocentre.Especially the nearshore subaqueous fan within low system tract,which are the most favorableness zone for sandstone reservoir.Syn-sedimentary faults have various of combination of styles including ＂ren＂ or ＂zhi＂ characters shape etc.have bring up changing construction palaeogeomorphology and ramp system which control the sandbody decentralized system and the accumulation mode.Revealing syn-sedimentary faults zone activity and distribution and rebuilding each stage of construction palaeogeomorphology and ramp zone are the key to the prediction of sedimentary system distribution and sandbody distribution.