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Jingeng Sha, Nanjing Institute of Geology and Palaeontology (China)
Yanhong Pan, Nanjing Institute of Geology and Palaeontology (China)
Huawei Cai, Nanjing Institute of Geology and Palaeontology (China)
Yaqiong Wang , Nanjing Institute of Geology and Palaeontology (China)
Xiaolin Zhang, Nanjing Institute of Geology and Palaeontology (China)
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Since the Late Triassic, an extensive regression mainly caused by the Indo-China movement has taken place in Asia. During the Jurassic, most part of China became land and rivers and lakes formed, which are usually very big in west but small in east China. The Tethys was limited to the Qinghai-Xizang (Tibet) Plateau, southwestern China, including Xizang, southern Qinghai, southwestern Yunnan, western Sichuan and Yunnan provinces. On east Chinese continent three Jurassic embayments opened into the western Palaeo-Pacific Ocean: an Early Jurassic lingual embayment of Guangdong-Jiangxi, extending northwards from Hongkong and Guangzhou to southwestern Hunan and western Fujian; two small and narrow embayments, Suibin and DongˇŻan embayments, in the northeastern corner of eastern Heilongjiang, northeastern China, both of Late Jurassic-Early Cretaceous age. The Nadanhada terrane in eastern Heilongjiang and probable Taiwan Island were inundated by the Palaeo-Pacific Ocean in the Early-Middle Jurassic. All marine Jurassic stages including the strata spanning the Triassic-Jurassic and Jurassic-Cretaceous boundaries, are recorded in Qinghai-Xizang Plateau, though the facies varies from ambyssal to marginal marine depending on geographical location and age.
The terrestrial Jurassic contains abundant fossils such as plant mega- and microfossils including spores and pollen grains, charophytes and dinoflagellate cysts, gastropods, bivalves, conchostracans, ostracods, insects and vertebrates including dinosaurs. It is mainly composed of fluvial and lacustrine clastic rocks, which bear thick coal beds in north but only coal seams in southern China. In eastern China, the Jurassic volcanic rocks are fairly common but rare or even absent in the west. Furthermore, the marine Jurassic rocks (e.g., in the Tanggula Mountains and Hohxil, northern Qinghai-Xizang Palateau) are intercalated with non-marine beds with fresh-water fossils such as the unionids (Bivalvia), and the terrestrial Jurassic deposits are in some cases (e.g., in the Juggar Basin of northern Xijiang Province, west China) associated with brackish-water or even marine fossil-bearing intercalations.
By means of the index fossils, particularly the non-marine beds occurring within marine rocks and marine and/or brackish intercalations in terrestrial deposits, serve in correlating terrestrial and marine strata. These strata could further be correlated with the international chronostratigraphic framework chart. The geological age of the terrestrial rocks could further be dated by the radiometric measurements of volcanic rocks.
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