摘要
一般认为经典层序的湖 (海 )平面变化轨迹为正弦曲线 ,且可分出低位稳定、上升、高位稳定和下降 4个阶段。按照Vail的层序地层学理论 ,每个三级层序由 3个体系域组成 ,目前也有人认为划分出 4个体系域更合适。但在断陷湖盆中 ,发育了一种特殊的层序 ,其湖平面变化呈折线 ,仅可分出上升阶段 (T)和下降阶段 (R) ,缺失稳定阶段 ,我们将此类层序称为T R层序。潮湿气候条件下的幕式构造运动和沉积物快速充填是T R层序形成的关键。层序发育的早期阶段 ,幕式构造运动产生新生可容空间 ,决定了T旋回的发育 ,形成了以深水泥岩、页岩等沉积为特征的湖侵域 ;晚期阶段 ,沉积物快速充填减少可容空间 ,决定了R旋回的演化 ,形成了以前积式砂体为特征的湖退域。T R层序与油气勘探关系密切 ,湖侵域烃源岩发育 ,湖退域储层发育 ,并具有良好的生储盖组合条件。
According to Vail's classical sequence stratigraphy, a sequence was composed of three system tracts, LST, TST and HST. Some geologists represented four system tracts, LST, TST, HST and FSST. The T R sequence, discussed in this paper, only consisted of two system tracts: lacustrine transgressive system tract (LTST) and lacustrine regressive system tract (LRST). Lacustrine deposits were mainly controlled by tectonic movements, sediment applies and climate changes in rift basin, with sequence strata being synthetical products of these controlling factors. The lake level curve of some sequences in rift basin was only composed of two change stages, i.e., rising stage and falling stage. Moreover, the sequence bottom boundary was not corresponding to a regional unconformity. These sequences could not be well explained by Vail's classical sequence stratigraphy, and named the T R sequence. The Cenozoic Dongying Depression in eastern China might be an example. In a stage of humidity climate, the episodic tectonic movement (fault) and the quick filling of sediments were key factors for the formation of T R sequence. In the early period of T R sequence, the episodic structural movement led to the quick decline of the lake basement, the fast increasing of the accommodation space and the quick falling of the lake level. When the tectonic movement weakened or stopped, the lake level began to rise quickly with the infusion of water. LTST formed in this period, when mainly deposited the deep water mudstone, with relatively thinner sediments, usually from several meters to decades meters. In the later period, the basin was full of water, and the lake level also kept stable. With lots of continental debris flowing into the basin, the quick filling of sediments would resulted in the decline of the relative lake level, the shoreline moving forward the basin and the decreasing of the accommodation space. In this period, LRST formed, which was featured by abundant sandstone bodies, with thick sediments as much as several hundred meters. The sandstone bodies usually enriched in LRST, and better source rocks formed in LTST, which was different from the distribution rules of sandstone bodies and source rocks in the Vail's sequence stratigraphic model.
出处
《地质科学》
CAS
CSCD
北大核心
2004年第1期111-122,共12页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家"十五"科技攻关 (编号 :2 0 0 1BA60 5A0 9)
中石化"十五"科技攻关 (编号 :P0 1 0 1 3 )
山东省自然科学基金 (编号 :Q2 0 0 3E0 1 )项目资助
关键词
经典层序
平面变化轨迹
幕式构造运动
控制因素
断陷湖盆
T R sequence, Episodic structural movement, Controlling factors, Lacustrine deposits, The Dongying Depression
