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Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 Jurassic of Continental Jungger Basin of West China. Xinjiang Geology, 2000, 18(1): 28-31 (in Chinese with English abstract). Cox L.R. Isognomonidae. In: Moore R. C. (ed). Treatise on Invertebrate Paleontology, Pt. N, Mollusca, 6, Bivalvia 1, Systematic Descrip- tion.The Geological Society of America and the University of Kansas Press, Bo, Co & Lawrence, Ka., 1969: 321-326. Deng S. H., Yao Y.M., Ye D.Q., et al. Jurassic system of North China, Vol. 1, Stratum Introduction. Beijing: Petroleum Industry Press, 2003. Gu Z.W., Huang B.Y., Chen C.Z., et al. Fosssil lamelli- branches of China. Beijing: Science Press, 1976: 522pp (in Chinese). Gu Z.W., Chen C.Z., Li J.H., et al. Waagenoperna (Waagenoperna) and its distribution in the “Lower Jurassic” of south China. Acta Palaeontologica Sinica, 1980, 19(6): 445-459 (in Chinese with English abstract). Hayami I. A Systematic Survey of the Mesozoic Bi- valvia from Japan. Univ. Mus., Univ. Tokyo, 1975, Bull. No.10. Liu B.P., Li Z.S. Triassic Bivalvia. In: Mesozoic stratigraphy and palaeontology in Shaanxi-Gansu- Ningxia Basin of China, 2. Beijing: Geological Publishing House, 1980: 1-26. (in Chinese). Lu Y.Z., Deng S.H. Triassic-Jurassic Sporopollen 244 Assemblages on the Southern Margin of the Junggar Basin, Xinjiang and the T-J Boundary. Acta Geologica Sinica, 2005, 79(1):15-27 (in Chinese with English abstract). Nakazawa K., Newell N. D. Permian bivalves of Japan. Mem. Fac. Sci. Kyoto Univ., ser. Geol. & Min., 1968, 35(1): 1-108. Reed F.R.C. Paleozoic and Mesozoic Fossils from Yunnan. Pal. Indica, 1927, Vol. X. Mem. No. 1. Tokuyama A. “Bakevellia” and “Edentula” from the late Triassic Mine series in west Japan. Transac- tions and Proceedings of the Palaeontological Society of Japan. New Series, 1959, 35: 147-155, pl. 16. Waagen L. Die Lamellibranchinten der Pachycar- dientuffe der Seiser Alm. Geol. R.A. Wien, Aphandl., 1907, 18(2): 1-188. Taf. 25-34. Xu J.F. Some Brackish-water Lamellibranchia from Xujiahe Formation of Upper Triassic in Hulukou of Weiyuan, Sichuan. In: Continental Mesozoic stratigraphy and paleontology in Sichuan Basin of China. Chengdu: People’s Publishing House of Sichuan, 1984: 520-528 (in Chinese). Zhang R.J., Wang D.Y., Zhou Z.Y. Bivalvia. In: Hubei Institute of Geology Research. (ed). Paleontolo- gical Atlas of central and south China. Beijing: Geological Publishing House, 1977: 1-332 (in Chinese).
Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 The Discovery and Preliminary Study of Middle Jurassic Silicified Wood in Qijiang, Chongqing Hui Ouyang, Feng Zhang Chongqing museum of natural history, Chongqing 410003, China (E-mail: Oyh_8@163.com) The study of silicified wood in China has several decades, many different authors have researched the wood fossils from various geological ages in many provinces (Si, 1951, 1953, 1962; Si et al.,1963; Xu, 1953; Cheng et al., 1980; Wang et al., 1994; Feng et al., 1998; Duan, 1986,2000; Duan et al., 1998, 2002; Dong et al., 2002; Nian et al., 2003; Zhu et al., 2003; Yang et al., 2004; Wang et al, 2006). There is a long history of wood record in Chongqing, while the beginning of research on them is marked by the preliminary study of Qijiang silicified wood flora. The flora was discovered in 2005 and the excava- tion and research work were made by Chongqing museum of natural history. The buried site is Masan- gyan quarry of Wenlong village, Gunan town, Qijiang county. More than 20 wood specimens were found in approximate 1000 square meters, but none was exposed completely. Among them the largest one is over 25 meters in length, with the top and root of the fossil still unseen. The diameter of two trees is about 1 meter. There are many places of wood fossils in Chong- qing, and Qijiang flora is the typical one of the most concentric buried and best preserved. The field investi- gation showed that the buried area of wood fossils is probably over one square kilometer. The surface of wood is deeply coalfield, while its internal wood fiber part is various mineralized including silified and limo- nitized etc. The forming mechanism is distinct from those of other fossils. Qijiang silicified wood flora is the direct evidence of large trees at that time in this area, and has important significances not only in paleobotany, but also in stratigraphy, paleo-environment, paleontology, paleoecology of Chongqing as well as adjacent areas. The Qijiang county is located in the joint of Sichuan basin and southeast Yungui plateau. The Indo-China orogenesis at the end of Triassic caused the margin of Sichuan basin to uplift as mountains. The original sea basin turned into a terrestrial one, and the ‘Bashu Lake’ was formed which almost occupied the whole basin area. In middle Jurassic a tectonic movement changed the sedimentary background of basin. As a result, the period of lacustrine facies de- veloping turned into that of terrestrial fluvial facies, producing a large distribution of thick-bedded sandstone. Silicified wood have been for the first time discovered from Middle Jurassic Upper Shaximiao Formation in Masangyan as referred above. The wood fossils were buried in middle medium coarse grained lithic feldspar quartz sandstone. In this area, Jurassic is represented by a terrestrial facies red fragment rock series in river and lake sedimentary environment. In addition, Middle Jurassic Suining formation, Upper Jurassic Penglaizhen formation as well as Early Creta- ceous Jiaguan formation are also exposed in this area. The wood fossils are relatively completely preserved, with large and small branches. Their features of morphology are similar to the type of Araucaria cuminghamia (needs a further study on cell structures). Most wood is buried parallel to the plane of strata. Fossils lie in the excavated area of 1000 square meters, and are distributed vertically along the surface of rock bed because the dip of strata is basically consistent with the slope direction, some woods’ direction are perpendicular or oblique to the dip. All woods under- went mineralization, with dark black or brown yellow appearance, hard and heavy, emit sparks when hit by a hammer. Some structures such as the external scars of bark, annual rings and even wood fiber structure can be observed in their sections. The trunk of trees is round or oval, the diameters are usually 50-60 cm, and the large one is more than 100 cm. The bark are morphologically clear, the surface is as black as coal. The interior color is mainly black with some dark black. The largest wood is more 25 meters long, with the top and root could unseen, so its whole length is estimated more than 30 meters. The branches are round; the diameter is 10-20 cm, usually incomplete. The exterior surface is cinnamon-like, 0.5 cm in thickness, and very easy to drop off. Parts of the wood surface are brown yellow as a result of limoni- tization. According to the observation of micro-structure of thin sections under the microscope, some part of cell tissue structures are still well preserved. The discovery of Qijiang wood flora shows that a large forest composed of high trees existed in Chongqing as well as neighbouring region during Middle Jurassic. The horizon of Qijiang wood fossils is the Middle Jurassic Upper Shaximiao formation. Araucarioxylon zigongensis has ever been founded in Lianggao moun- tain, Zigong, which is near to the famous Dashanpu buried site of dinosaurs, the distance is only 3.5 kilo- meters, the horizon is Lower Shaximiao formation, so the age of Qijiang wood fossils are later than that of Zigong wood. In Yibing, Sichuan, Jiangan wood flora was 245
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