纵向伸展断背斜类型及成因

doi:10.19657/j.geoscience.1000-8527.2021.186

摘要/Abstract

摘要：

纵向伸展断背斜是伸展断陷中重要的油气勘探领域。按照断背斜的几何形态将纵向伸展断背斜划分为双断型断背斜、单断型断背斜和叠合y型断背斜。根据渤海湾盆地新生代地质资料,讨论这3类纵向伸展断背斜的成因:(1)双断型断背斜发育于裂谷期,受对向双断断陷控制,主要是由于早期伸展过程中岩层局部缩短作用、晚期差异沉降和断块翘倾作用形成,其形成机制不同于前陆盆地的区域挤压作用产生的背斜;(2)单断型断背斜(或称逆牵引背斜)发育于裂谷期,受单断断陷控制,是由于控陷断层下降盘岩层下滑过程中岩层以逆牵引方式回倾、差异沉降和岩层弹性挠曲作用造成的,但岩层长度局部缩短作用仍是一个重要因素;(3)叠合y型断背斜发育于裂谷期后,受对称断陷和其中y形断洼控制,其形成与以纯剪切方式伸展运动和多期次断裂活动有关。它与走滑-伸展断背斜成因存在根本性差别,后者实质上不属于纵向伸展断背斜的范畴。

关键词: 纵向伸展断背斜, 岩层局部缩短作用, 伸展运动学模式, 走滑-伸展叠合y型断背斜

Abstract:

Longitudinal extensional faulted anticline in extensional fault-bounded depression is an important oil and gas exploration field. According to faulted anticline geometry, these anticlines can be divided into double- faulted (a pair of normal faults) anticline, single-faulted anticline, and superimposed y-type faulted anticline. Based on Cenozoic geological data of the Bohai Bay Basin, origin of these three kinds of faulted anticlines is suggested as follow: (1) Double-faulted anticline is developed in rift valley stage, and is controlled by a pair of normal faults with face-to-face dipping mode. Its fault-bounded depression is mainly caused by local rock shortening during the early-stage regional extensional, differential subsidence and fault block tilting occurred in the late stage; (2) Single-faulted anticline is developed in the rift valley stage, and is controlled by single extensional fault-bounded depression. It is likely caused by the reverse traction, differential subsidence, and elastic flexure of rock formation during the descending process of the fault-bounded depression. Nonetheless local rock formation shortening is still a major factor; (3) Superimposed y-type faulted anticline is developed in post-rift stage and controlled by symmetric fault-bounded depression and the y-type faulted sag (i.e.fault-bounded sub-depression) among them. It is fundamentally different from the cause of strike-slip and extensional superimposed y-type faulted anticline, which does not actually belong to the longitudinal extensional faulted anticline category.

Key words: longitudinal extension faulted anticline, local rock formations shortening, extensional kinematics model, strike slip-extensional superimposed y-shaped faulted anticline

中图分类号:

TE121.2

陈发景, 陈昭年. 纵向伸展断背斜类型及成因[J]. 现代地质, 2021, 35(06): 1789-1796.

CHEN Fajing, CHEN Zhaonian. Types and Causes of Longitudinal Extensional Faulted Anticline[J]. Geoscience, 2021, 35(06): 1789-1796.

图/表 10

图1 黄骅凹陷南区地质横剖面及位置图(据周建生,1997) (a)黄骅坳陷伸展构造体系示意图;(b)黄骅凹陷南区地质剖面图

Fig.1 Geological profile and location map of the southern Huanghua Depression

图2 伸展双断型断背斜的形成横剖面示意图

Fig.2 Sketch profile showing the formation of double-faulted anticline

图3 TBB-85-NW444测线剖面及其位置图(据汤良杰,1989)

Fig.3 TBB-85-NW444 seismic line profile and its location map

图4 马西逆牵引背斜地震解释剖面图(据王夑培,1990)

Fig.4 Seismic interpretation section of the Maxi reverse traction anticline

图5 单断型断背斜形成示意剖面图

Fig.5 Sketch profile showing the formation of single-faulted anticline

图6 黄河口凹陷地震剖面显示叠合y型断裂及其间背斜(据陈发景,2008)

Fig.6 Seismic profile of the Yellow River estuary depression, showing the superimposed y-type faults and anticlines among them

图7 渤中西洼叠加y型断裂及其间断背斜剖面图(据李龙等,2018修改)[11]

Fig.7 Sketch profile of the superimposed y-type faults and faulted anticlines among them in the western Bozhong sag

图8 伸展运动学的纯剪切和简单剪切模式示意图(据Jackson A,1987)

Fig.8 Sketch map showing pure shear and simple shear models of extension kinematics

图9 辽河盆地燕南构造走向—伸展叠合y型断背斜(据邱华标,2011)

Fig.9 Yannan strike slip-extensional superimposed y-type anticlines in the Liaohe Basin

图10 辽东湾坳陷东部边缘横剖面图(据漆家福,1995)

Fig.10 Cross-section across the eastern margin of the Liaodongwan depression

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