辽东湾—下辽河盆地新生代构造的运动学特征及其演化过程

辽东湾－下辽河盆地是一个富含油气的新生代裂陷盆地。裂陷作用使盆地区的地壳或岩石圈被不同尺度的断裂肢解为形体各异的断块体,并使这些断块体在复杂而有规律的运动过程中形成了裂陷盆地及盆地中的两个相对独立而又有关联的新生代构造系统──伸展构造和走滑构造。盆地构造的运动学特征可以用断块间的相对运动和断块体本身的运动来描述,包括水平伸展运动、差异升降运动、相对走滑运动和断块体掀斜运动等四种主要形式。本文描述和讨论了各种形式的“运动”在辽东湾－下辽河盆地中的表现特征,测算了新生代盆地的伸展量、沉降量等主要构造运动学参数,并在此基础上将盆地的新生代构造演化划分为早第三纪裂陷阶段和晚第三纪－第四纪后裂陷阶段。早第三纪的裂陷事件具有分期次、呈幕式的特点,进一步可以分为始新世和渐新世两个具不同特色的伸展幕。

KINEMATIC CHARACTERISTICS AND EVOLUTION OF THE CENOZOIC TECTONICS IN LIAODONGWAN-XIALIAOHE BASIN

Liaodongwan-Xialiaohe basin is a Cenozoic plate interior rifting basin. The faultedblock movement of the basin can be decomposed into different styles: (1) extensional horizontal movement; (2) differential vertical movement; (3) block tilting movement and (4) inter-block strike-slip movement. The amount of extension (about 20% ) of the basin is estimated by using balance section technique, and the main extensional events occurred during the Eogene. The subsidence history of the basin is shown to consist of two distinct stages. The first stage characterized by rapid subsidence (the rate of basement subsidence about 0. 2￣0. 5 mm/a) during the Eogene is correlated with associated rifting extensional events. The subsidence of the second stage during Neogene to Quaternary is much slower (about 0. 02￣0. 06 mm/a) and is attenuated in exponential form. On the basis of the kinematic characteristics and depositional sequence of the basin, the evolution of the Cenozoic tectonics can be divided into two distinct stages: the rift stage during the Eogene and the post-rifting stage during the Neogene to Quaternary. The former including a series of extensional events can be further divided into two different extensional episodes: the Eocene and the Oligocene. During the Eocene, rapid extension and subsidence are caused by basement-block tilting movement. During the Oligocene,the strike-slip movement caused by reactivation of "the Tanlu deep fault system" is superposed to the tectonic of rapid extension and subsidence.