The Tertiary evolution of the prolific Nanpu Sag of Bohai Bay Basin, China: Constraints from volcanic records and tectono-stratigraphic sequences
The Tertiary evolution of the prolific Nanpu Sag of Bohai Bay Basin, China: Constraints from volcanic records and tectono-stratigraphic sequences
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中国渤海湾盆地南堡凹陷第三纪演化：火山记录和构造地层序列的制约
DOI：
10.1130/b30041.1
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发表时间：
2010-03-01
影响因子：
4.9
通讯作者：
Huang, Hongxiang
中科院分区：
文献类型：
--
作者：
Dong, Yuexia;Xiao, Long;Huang, Hongxiang
渤海湾盆地位于亚洲东部边缘，是中国第二大产油盆地。南堡凹陷因近年来的重大石油发现而显得尤为重要。然而，在地质构造上，该盆地的裂陷机制和地球动力学演化仍不确定。本文利用南堡凹陷大量钻探和取样获得的火山岩和地层记录，对盆地构造-地层层序进行了解释，并对盆地动力学演化和壳幔相互作用进行了探讨。
南堡凹陷发育大量以碱性玄武岩为主的火山岩。钻井岩心样品、测井记录和地震剖面揭示了始新世和中新世之间的三个火山旋回。这些玄武岩是在石榴石-尖晶石橄榄岩的过渡过程中形成的。在此基础上，识别出5个幕式大陆裂谷作用形成的构造-地层层序，分别由基底粗碎屑岩层序、下部火山岩层序、中部深水碎屑岩层序和上部充填层序组成。
南堡凹陷构造演化经历了四个阶段。前三个对应于旋回火山作用和沉积沉积特征所揭示的三次裂谷事件。第四阶段为强烈热沉降和逆冲河流沉积，随后发生构造反转。提出了一个底辟上地幔上涌模型，用以解释南堡凹陷和大渤海湾盆地的多次裂谷作用、旋回性火山作用和周期性构造演化的动力学机制。
The Bohai Bay Basin, located on the eastern Asian margin, is the second largest oil-production basin in China. It contains numerous depressions and sags, among which Nanpu Sag has become particularly important because of significant oil discoveries in recent years. Geologically and tectonically, however, the rifting mechanism and geodynamic evolution of the basin remain uncertain. This paper uses detailed volcanic and stratigraphic records obtained through extensive drilling and sampling in Nanpu Sag to interpret tectono-stratigraphic sequences and discuss basin dynamic evolution and crust-mantle interactions of the Bohai Bay Basin.
Nanpu Sag contains voluminous volcanic rocks of dominantly alkaline basalts. Drill core samples, well logs, and seismic profiles reveal three volcanic cycles between the Eocene and Miocene Epochs. These basalts were created during a transition from garnet- to spinel-peridotite. Five tectono-stratigraphic sequences produced by episodic continental rifting have been identified, each composed of a basal coarse clastic sequence, a lower volcanic sequence, a middle deep-water clastic sequence, and an upper infilling sequence.
Tectonically, Nanpu Sag experienced four evolutionary phases. The first three corresponded to three rifting events revealed by cyclic volcanism and sedimentary depositional features. The fourth phase was marked by extreme thermal subsidence and prograding fluvial deposition followed by tectonic inversion. A diapiric upper-mantle upwelling model is proposed to explain the dynamics that controlled the multiple rifting processes, the cyclic volcanism, and the periodic tectonic evolution of Nanpu Sag and the greater Bohai Bay Basin.