FIELD TRIP GUIDE Xianghui Li, Wen Lai, Guang Hu, Shuzhong Shen, Xiumian Hu TABLE of CONTENTS
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International Workshop on Climate and Environmental Evolution in the Mesozoic Greenhouse World & 3rd IGCP 609 Workshop on Cretaceous Sea-Level Change Cretaceous stratigraphy and sedimentology in southeastern China Nanjing University, China September 8–11, 2015 FIELD TRIP GUIDE Xianghui Li, Wen Lai, Guang Hu, Shuzhong Shen, Xiumian Hu TABLE OF CONTENTS Introduction .............................................................................................................. 1 Day 1 (September 8th): Nanjing-Changxing-Jiande ................................... 6 Stop 1-1 The Pukou Formation, Upper Cretaceous ................................................. 6 Stop 1-2 The Chishan Formation, Upper Cretaceous .............................................. 7 Stop 1-3 The Meishan P/Tr GSSP Section ............................................................. 10 Day 2 (September 9th): Jiande-Guixi-Quzhou ............................................ 18 Stop 2-1 Intermountaine mollase facies, Hekou Formation of Guifeng Group, Upper Cretaceous.................................................................................................... 18 Stop 2-2 Large-scale aeolian facies, Tangbian Formation of Guifeng Group, Upper Cretaceous............................................................................................................... 20 Day 3 (September 10th): Quzhou-Longyou-Jiande-Shipu ...................... 23 Stop 3-1 Lacustrine facies, Jinhua Formation of Quzhou Group, Upper Cretaceous ................................................................................................................................ 23 Stop 3-2 Volcanic-sedimentary successions and paleosol facies of the Lower Cretaceous Jiande Group ........................................................................................ 24 Day 4 (September 11th): Shipu-Nanjing ........................................................ 29 Stop 4-1 Transitional facies, Shipu Group, Lower Cretaceous .............................. 29 Reference .................................................................................................................. 34 Introduction The South China block (SCB) consists of the Yangtze block to the northwest and the Cathaysian block to the southeast (Fig. 1). The present boundary between these two blocks is the northeasterly trending Jiang-Shao fault. The timing of the amalgamation between the Yangtze and Cathaysian blocks remains controversial. The predominant view was an early Neoproterozoic age for the amalgamation, ca. 900 to 880 Ma to ca. 800 Ma. During the Phanerozoic time, the south China block experienced four main tectonic events. 1) The Kwangsian orogeny, which is traditionally called the Chinese Caledonian orogeny, is characterized by the angular unconformity that separates the Devonian-Permian cover from strongly deformed pre-Devonian strata as well as syn-deformational metamorphism and subsequent anatexis. It is generally considered to be an early Paleozoic intracontinental orogen; 2) Late Paleozoic extensional rifting, which probably started in the Devonian; 3) the collision between South China and North China blocks during Middle to Late Triassic along the Su-Lu-Dabie-Qinling suture zones; 4) The Indosinian orogeny, which extended from the Late Permian to the Middle Triassic, was a result of the collision between the Indochina block and South China; 5) Late Mesozoic magmatism along the southeastern coast of South China, which represents an active continental margin. Fig. 1. Sketch map of East China (Hu et al., 2012) 1 The Cretaceous is an important period in geological time, and has also witnessed notable evolution and extinction of marine and terrestrial biotas. Among the most important and several issues faced by the international community are the greenhouse effects and global climate changes (Wan et al., 2007). Cretaceous deposits are widespread in China. Most strata are of nonmarine origin, and marine sediments occur only in Tibet, western Tarim of Xinjiang, Taiwan and limited area of eastern Heilongjiang. The nonmarine deposits are outlined from northeast China, southeast China, southern interior China, southwest China, the Shaanxi-Gansu-Ningxia region, and northwestern China intermontane basins. The sedimentary facies and paleogeography are diversified (Wan et al., 2007). Nonmarine Cretaceous strata in the coastal areas of southeastern China are quite different from those of northeastern China, and are composed mainly of volcanics, red beds and variegated deposits intercalated with evaporites at the top, which reach substantial thicknesses; coal is absent. The Lower-Upper Cretaceous boundary in this region has also been subject to varying interpretations, but recently-discovered fossils from the Chaochuan Formation in Zhejiang are known to be of the Cenomanian in the Hekou Formation of Fujian, thus the boundary in Zhejiang can be placed between the Chaochuan and Guantou formations. Another relatively complete nonmarine Cretaceous sequence, which includes 10 formations, has been established in this region (Wan et al., 2007). During the Cretaceous, the continental interior of China was characterized by large lake systems in tectonic depressions and intermontane basins, with little or no marine influence. During the Cretaceous, most of southern China was characterized by very warm, dry climates, resulting in the deposition of extensive continental red beds, gypsum, and rock salt in large water-filled depressions and intermontane basins (Fig. 2, 3; Chen., 1987). 2 Fig. 2. Sketch map showing the early Early Cretaceous (Neocomian) paleogeography in China (Chen., 1987). 1 =Tethys Sea. 2= Pacific Ocean. 3= Wusuli Gulf. 4= Shu Lake. 5 = Xichang Lake. 6 = Yunnan Lake. 7= Puer Lake. 8= Ba Lake. 9 = Qingyang Lake. 10= ancient Datong River. 11= Chao Lake. 12= Junggar Basin. 13= Turpan Basin. 14= Kuqa Basin. 15= unnamed River. 16= Kashi Gulf. 17= Songhua Lake. 18= Yunmeng Lake. 19= ancient Gan River. 20= ancient Fuchun River. 21 = active volcanic zones in the eastern coastal low land. Fig. 3. Sketch map showing the early and middle Late Cretaceous (Cenomanian Santonian) paleogeography in China (Chen., 1987). symbols same as in Fig. 2. 3 A compilation of reliable isotopic age data indicates that Cretaceous magmatism in SE China (Fig. 4)occurred in four major episodes during 136–146 Ma, 122–129 Ma, 101–109 Ma and 87–97 Ma. A-type granitic and within-plate basaltic magmatism from 140–90 Ma suggests a dominant extensional environment in the region. Voluminous coeval high-K calc-alkaline rocks, which have geochemical features similar to those formed in continental back-arc and post-collision extension settings, are interpreted to have been generated in response to lithospheric extension. Cretaceous magmatism, NNE-trending wrench faulting and formation of extensional basin systems favour an extensional tectonic regime in SE China in the Cretaceous (Li., 2000). Fig. 4. Sketch map showing the distribution of the Cretaceous volcanic rocks in SE China (Li., 2000). 4 During the 4-day-excursion in southern Jiangsu, western Zhejiang and northeastern Jiangxi provinces (Fig. 5, Table 1), we will visit the rocks and sections from Early Cretaceous to Late Cretaceous. Major stops and attractions include: (1) Late Cretaceous continental deposits of Chishan Formation and Pukou Formation (Jiangsu Province); (2) the GSSP section of Permian-Triassic boundary in Meishan, Zhejiang Province; (3) Cretaceous continental deposits in Jiangxi and Zhejiang Province; (4) shallow marine deposits of Xiangshan Formation, Lower Cretaceous (Zhejiang Province). Table 1. The table of Cretaceous regional stratigraphical correlation in southeast China Epoch Nanjing Guixi Quzhou Jiande Shipu Chishan Fm. Lianhe Fm. Quxian Fm. K2 Tangbian Fm. Fangyan Fm. Pukou Fm. Hekou Fm. Jinhua Fm. Hengshan Fm. Ganzhou Group Shouchang Fm. K1 Gecun Fm. Zhongdai Fm. Shipu Fm. Huangjian Fm. Huobashan Group Laocun Fm. Fig. 5. The sites of 3rd IGCP 609 workshop field excursion 5 Day 1 (September 8th): Nanjing-Changxing-Jiande Schedule: 8:00-8:40, Nanjing University to Yanziji Park 8:40-9:40, [Stop 1-1:Yanziji Park, Nanjing]. Investigating the Pukou Formation, Upper Cretaceous 9:40-10:40, Yanziji Park to Chishan 10:40-11:40, [Stop 1-2:Chishan Mountain, Jurong]. Investigating the Chishan Formation, Upper Cretaceous 11:40-12:40, lunch in Bus 11:40- 14:00, Chishan to GSSP Park, Changxing 14:00- 16:00, [Stop 1-3:GSSP Park, Changxing]. Investigating the Meishan P/Tr GSSP Section. 16:00-19:30, Changxing to Jiande 19:30-, dinner and accommodation in the Kaiyue Hotel, Jiande City Highlight: Pukou Formation and Chishan Formation (Upper Cretaceous sequences), the Meishan P/Tr GSSP Section. Stop 1-1 The Pukou Formation, Upper Cretaceous Location: Yanziji Park, Nanjing city, Jiangsu province Time: 1 hour Background: The Pukou Formation (K2p) of Upper Cretaceous has been deposited in Wangjing, Qianshan, Wuwei, Nanxuan, Changzhou, Jurong, Nanjing, Quanjiao, and Subei of the Lower Yangtze Region (Shang et al., 2002). The Pukou Formation covers unconformably on the Gecun Formation or the volcanic rock, and is possibly conformably covered by the Chishan Formation. The Gecun Formation is mainly composed of greyish-green siltstone and mudrocks. The Pukou Formation (K2p) is composed of variable clastic lithologies, such as conglomerates, sandstone, siltstone, mudrocks, gypsum-salt rock. The lower part of the Pukou Formation is dominated by conglomerates, grayish purple vocanic conglomerates and sandstone.