The Tertiary evolution of the prolific Nanpu Sag of Bohai Bay Basin, China: Constraints from volcanic records and tectono-stratigraphic sequences

Abstract

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 signifi cant 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 crustmantle interactions of the Bohai Bay Basin. Nanpu Sag contains voluminous volcanic rocks of dominantly alkaline basalts. Drill core samples, well logs, and seismic profi les 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 identifi ed, each composed of a basal coarse clastic sequence, a lower volcanic sequence, a middle deep-water clastic sequence, and an upper infi lling sequence.Tectonically, Nanpu Sag experienced four evolutionary phases. The fi rst 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 fl uvial 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.

Sequence-stratigraphic architectures and sand-body distribution in Cenozoic rifted lacustrine basins, east China

“…These identified that sequence boundaries may not exactly correspond to the traditional lithostratigraphic or formation boundaries in these basins or subbasins. The ages of major sequence boundaries were determined from biostratigraphy (correlatable timeequivalent standard lacustrine fossil assemblages) and calibrated by paleomagnetic data and isotope ages of volcanic rocks (e.g., Wang and Qian, 1992;Yao et al, 1994;Song et al, 2003;Li, 2004;Qiu et al, 2006;Yang et al, 2006;Li, 2008;Yan et al, 2008;Liu et al, 2009;Zhang et al, 2009;Dong et al, 2010).…”

“…This is attributed to the fact that these rifted lacustrine basins in east China are situated in the same tectonic setting, where similar age riftings and unconformities were developed because of the subduction of the West Pacific Plate and episodic upper-mantle upwelling (Li et al, 1997;Ren et al, 2002;. Also, the similar basin evolution episodes and tectonic history in these basins can be revealed by similar cyclic volcanic eruptions between basins, which represent different stages of continental rifting with specific age intervals (Chen et al, 1999;Song et al, 2003;Dong et al, 2010).…”

Volcanism of the Nanpu Sag in the Bohai Bay Basin, Eastern China: Geochemistry, petrogenesis, and implications for tectonic setting

“…Thus, we argue that these Cenozoic basalts were generated in an intra-continental setting associated with continental rifting in eastern China that might have been triggered by an asthenospheric mantle upwelling and partial melting. The episodic nature of the crustal uplift (Dong et al, 2010) and corresponding OIB-like volcanism in the Bohai Bay Basin area are also best explained by a lithospheric interaction with an upwelling asthenospheric mantle.…”

“…Age data used for calculating Sri and eNd is 40 Ma, 35 Ma and 23 Ma (Dong et al, 2010) for Cycle-1, -2 and -3 basalts.…”

Late Holocene slip rate and average recurrence interval of great earthquakes on the Shangzhi segment of the Yilan‐Yitong Fault Zone, northeastern China: Constraints from paleo‐earthquakes and historical written records

“…Although there is a lack of written records of strong earthquakes due to the underdeveloped ethnic minorities, changes in the languages, natural hazards and ongoing wars between minority groups, the YYFZ has been speculated to have the greatest deformation and highest gradient of stress accumulation and thus to be the most likely location for potential catastrophic earthquakes because it is the main boundary fault between the active tectonic blocks of Xingan‐East Mongolia, Yanshan and Northeast China (Zhang et al, , ). Over the past several decades, its structural features (Liu et al, ; Shi et al, ; Su et al, ; Tian & Du, ; Tong, Yu, & Geng, ; Zhu et al, ), Mesozoic–Cenozoic evolution (Dong et al, ; Gilder et al, ; Hsiao et al, ; Huang et al, ; Xu & Zhu, ; Zhu, Niu, Xie, & Wang, ; Zhu, Zhang, Xie, Niu, & Wang, ), relationships between faults and basins (Allen, Macdonald, Xun, Vincent, & Brouet–Menzies, ; Chen et al, ; Chen & Nábelek, ; Tang, Yang, Guo, & Tang, ; Yu, Min, Wei, Zhao, & Ma, ; Yu et al, ; Zhang et al, ; Zhang, Min, Deng, & Mao, ; Zhang et al, ; Zhou et al, ), potential oil and gas resources (Wang, ; Yang & Xu, ) and regional geodynamic processes (Fletcher, Fitches, Rundle, & Evans, ; Huang & Zhao, ; Ren, ; Ren, Lu, Li, Yang, & Zhuang, ; Ren, Tamaki, Li, & Zhuang, ; Wu, Xu, Zhu, & Zhang, ; Yin, ; Yin & Nie, ; Zhang, Zheng, Zheng, Wang, & Zhang, ; Zhao, ; Zhu, Chen, Wu, & Liu, ; Zhu et al, ) have been studied intensively. However, many controversial issues about the late Quaternary deformation of the YYFZ remain, especially with respect to its slip rate and the average recurrence interval of major earthquakes in the late Quaternary.…”