Present-day heat flow, thermal history and tectonic subsidence of the East China Sea Basin Shuchun Yang a, * , Shengbiao Hu a , Dongsheng Cai b , Xiaojie Feng b , Linlin Chen c , Le Gao b a Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China b China Offshore Oil Exploration and Development Research Center, Hebei 074010, People’s Republic of China c Bureau of Marine Geology of Shanghai MGRC, Shanghai, People’s Republic of China Received 17 September 2003; received in revised form 17 May 2004; accepted 20 May 2004 Abstract The East China Sea Basin is located in the convergence area between the Eurasian plate, the Pacific plate and the Philippine Sea plate, and consists of two depressions, the Taibei Depression in the west and the Xihu Depression in the east. Heat flow measurements show that the East China Sea Basin is characterized by present-day heat flow around 70.6 mW/m 2 , varying between 55 and 88 mW/m 2 . No significant difference in heat flow is observed between the Xihu and the Taibei Depressions. Thermal history reconstruction using vitrinite reflectance suggests that the thermal history was, however, different in the Taibei and the Xihu Depressions. Paleo-heat flow values when the pre- Tertiary formations experienced their maximum temperature at the end of the Paleocene reached a mean of 82 mW/m 2 in the Taibei Depression, much higher than the present-day value. The lower Tertiary sediments in the Xihu Depression experienced maximum temperatures at the end of Oligocene (35.4–23.3 Ma) and reached a mean paleo-heat flow value of 83 mW/m 2 . Tectonic subsidence analysis shows that the timing of the major rifting episode was different across the East China Sea Basin. The rifting occurred from the Late Cretaceous (w65 Ma) to the early Eocene (w55 Ma) in the Taibei Depression, followed by thermal subsidence from the late Eocene to the end of Miocene (23.3-5.2 Ma). In contrast, in the Xihu Depression the initial subsidence lasted until the early Miocene and thermal subsidence to the end of Miocene. From Pliocene to the present, an accelerated subsidence took place all along the West Pacific margin of Asia. Significant thicknesses of strata were removed from the unconformities in the basin: the mean amount of erosion was 1147 m from the Paleocene and 1208 m above the Oligocene in the Taibei Depression, and 1409 m from the Oligocene in the Xihu Depression. q 2004 Elsevier Ltd. All rights reserved. Keywords: East China Sea basin; Heat flow; Thermal history; Tectonic subsidence; Thermo-tectonic evolution 1. Introduction Many extensional basins, which contain significant petroleum resources, developed in eastern China after the late Mesozoic. These basins, both onshore and offshore, have a similar age and structural style. The sedimentation and structural geometry of these basins have been described in several earlier publications (e.g. Gilder, Keller, Luo, & Goodell, 1991; Li, 1984; Li, Mo, & Yang, 1995; Li, Yang, & Wu, 1987; Li, Yang, & Xie, 1997; Ma & Wu, 1987; Tian, Han, & Xu, 1992). The basins experienced episodic rifting stages, including late Mesozoic rifting, early Tertiary rifting, Neogene rifting and Quaternary rapid subsidence. The late Mesozoic rifting was caused mainly by the westward, subduction induced slab roll-back of the Pacific plate relative to the eastern margin of Asia (Cong, 1977; Tao, 1992). Early Tertiary rifting is grouped into two systems, continental rifting and a continental margin rifting, which might be caused by the steepening dip of the subducted oceanic slab (Pigott & Ru, 1994; Ru & Pigott, 1986). Oligo-Miocene, rifting formed pull-apart basins related to regional sinistral transform faulting, while a later phase of rifting was caused by E–W extension since the Pliocene (Kimura & Tamaki, 1986; Tapponnier & Molnar, 1979). Rapid, regional Quaternary subsidence has been observed all along the West Pacific margin of Asia. 0264-8172/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpetgeo.2004.05.007 Marine and Petroleum Geology 21 (2004) 1095–1105 www.elsevier.com/locate/marpetgeo * Corresponding author. E-mail addresses: ysc740316@mail.igcas.ac.cn (S. Yang), sbhu@ mail.igcas.ac.cn (S. Hu).