陆相断陷盆地层序类型与构造特征

Sequence Types and Structural Characteristics in ContinentalRift-Subsidence Basins

本文通过对中国东部古近纪—新近纪陆相断陷盆地层序地层的研究表明:陆相断陷盆地存在着同生断裂坡折带、同沉积构造挠曲坡折带两种基本坡折类型和无坡折的平缓地貌,由此决定了陆相断陷盆地有三种基本的层序类型,这就是同沉积断裂坡折型层序——A 型层序;同沉积构造挠曲坡折型层序——B 型层序;无坡折的平缓型层序——C 型层序。这三种层序在纵向上有规律的叠置组合就构成了盆地层序充填序列。断陷盆地层序的充填序列一般为C→A→B→C型,但也可发育成其他类型如A→B→C 型或 B→C型。同沉积断裂坡折型层序和同沉积构造挠曲坡折型层序的低位域砂体和高位域扇三角洲成藏条件优越、地震剖面易于识别是隐蔽油气藏勘探的主要目标。

Studies on the Tertiary sequence stratigraphy in East China continental rift-subsidence basins shows that there are two kinds of basic slope-break types, syndepositional fault slope-break zone and syndepositional structurally bent slope-break zone, and a gentle slope topography. So, three basic sequences, syndepositional fault slope-break sequence (Type A), syndepositional structurally bent slope-break sequence (Type B) and gentle slope sequence (Type C), are developed correspondingly. The three basic sequences, stacked regularly, constitute sequence-filling succession of continental rift-subsidence basins. Generally, the sequence filling succession of a continental rift-subsidence basin is C→A→-B→C, but others sequence-filling successions also are developed such as A→-B→C or B→C. Lowstand sand bodies and highstand fan delta sand bodies, favorable for hydrocarbon accumulation and identified easily on seismic profiles, are main subtle reservoirs of exploration aims.