08

Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66 – 71 www.elsevier.com/locate/palaeo

Discovery of Permian sporopollen from Daftar, Taxkorgan, Xinjiang and their geological implications Jianxin Yao a,⁎, Xuchang Xiao a , Lianda Gao a , Naiwen Wang a , Wenhua Ji b , Shiyan Wang c , Yong Wang a , Zhenqing Chi a a

b

Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China Academy of Regional Geology and Minerals Research, Bureau of Geology and Mineral Resources of Shaanxi Province, Xianyang, 712000, China c Regional Geological Survey Party, Bureau of Geology and Mineral Resources of Henan Province, Pingdingshan, 467021, China Accepted 30 November 2006

Abstract Tectonically located in the West Kunlun–Karakorum orogenic belt at the junction between the Indian plate and the Eurasian plate, the Daftar area, Taxkorgan County, Xinjiang Uygur Autonomous Region, is one of the most important regions for the research on geological evolution of the Karakorum–Kunlun Mountains. Located in the very cold anoxic area in the core of central Asia, natural conditions on the West Kunlun–Karakorum area are very challenging and roads are bad making field work difficult. Because the regional geology has been little studied, Permian microfossils have not been reported before. After field collection and research, the Permian sporopollen Endosporites punctatus Gao, Wilsonites delicatus (Kosanke) Kosanke, Cordaitina spongiosa (Luber) Samoilovich, Alisporites splendens (Leschik) Foster and Sulcatisporites ovatus (Balme and Hennelly) Balme were found recently in a clastic sequence in the Daftar area. Based on the evidence from Permian sporopollen, and data previously published on biostratigraphy and isotopic geochronology, the authors consider that the clastic sedimentary strata in Daftar area, previously regarded as Permian, may be a mélange composed of Silurian and Permian as well as other horizons of different ages. © 2007 Elsevier B.V. All rights reserved. Keywords: Permian; Sporopollen; Mélange; Karakorum–Kunlun Mountains

1. Introduction Tectonically located in the West Kunlun–Karakorum orogenic belt at the junction between the Indian plate and the Eurasian plate, the Daftar area, Taxkorgan County, Xinjiang Uygur Autonomous Region, is one of the most important regions for the research on geological evolution of the Karakorum–Kunlun Mountains. Located in the very cold anoxic area (average ⁎ Corresponding author. Tel.: +86 10 68999706; fax: +86 10 68997803. E-mail address: [email protected] (J. Yao). 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2006.11.056

altitude is 4000–5000 m, anoxic extent is 30% ∼ 50%) in the core of central Asia, natural conditions in the West Kunlun–Karakorum area are very challenging and roads are bad making field work difficult. Therefore, the regional geology of the area has been little studied. In the 1940s, the stratigraphy of marine carbonate rock and clastic rock exposed between Ageledaban and Karakorum mountain Pass was first assigned to the Upper Permian Balange Series (Belyaewski, 1947). Henceforth, this series was regarded as Permian, Carboniferous–Permian or Lower Permian (Second Geological team of Bureau of Geology and Mineral

J. Yao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66–71

Resources of Xinjiang Uygur Autonomous Region, 1985). The Editorial group of regional stratigraphic chart of Xinjiang Uygur Autonomous Region (1981) considered this series to be the Lower Permian Kongkashankou Formation composed of gray–black shale, sandstone and siltstone intercalated with few limestone beds, yielding brachiopods, corals and fusulinids: Neoschwagerina sp., Sumatrina sp., and distributed in Taxkorgan, upper reaches of Yeerqiang River and Karakorum mountain Pass. The Institute of Geology and Mineral Resources and First Regional Geological Surveying Party, Bureau of Geology and Mineral Resources of Xinjiang (1991) divided the Kongkashankou Formation into two parts, the lower part was named the Jiawendaban Formation, the upper part was still called the Kongkashankou Formation (Jin et al., 2000). According to the Permian fusulinids found in breccia limestone, bioclastic micrite, a large area of Permian rocks was indicated in the upper reaches of the Taxkorgan River. This discovery was shown on the Synopsis of the geological map and mineral map of the western part of South Xinjiang Uygur Autonomous Region (1:500,000) compiled by the Second Geological team of Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region (1985). Based on published data, Jiang et al. (1992, 2000) and Ding et al. (1996) divided the West Kunlun–Karakorum orogenic belt into three belts, a north belt, a middle belt and a south belt. Jiang et al. (1992, 2000) distinguished a marine facies in the middle and south belts, and a nonmarine facies in the north belt of Lower Permian. Ding et al. (1996) thought that the distribution of the Upper Paleozoic and Lower Mesozoic in the northern part of south belt is restricted along the southern side of the Mazha–Kangxiwa ductile shear zone and that the Upper Paleozoic and Lower Mesozoic in the southern part of the south belt is widely distributed over upper reaches of the Taxkorgan River and Karakorum River, but the stratigraphic sequences in outcrops are usually incomplete, and the rock types are quite complex. Wen et al. (2000) divided the West Kunlun– Karakorum stratigraphy into five stratigraphy provinces: Tarim, Kunlun, Bayankara, Karakorum and Qiangtang, and pointed out that Lower and Middle Permian are widely distributed in the Tarim, Kunlun, Karakorum and Qiangtang provinces. The Lower Permian is about 1000 m thickness and is composed of dark grey slate intercalated with quartz schist, lens-shaped sandstone and green schist (metamorphosed basic volcanic rock), the characteristic of flysch bedding is present in some sandy slate beds in the Daftar area of Taxkorgan County,

67

Zankan and East Mountain of Daohangzhan, and some pebbled slate is intercalated with the sandy slate beds, although no fossils were found in western Daftar area. On all accounts, the confirmation of age of Permian stratigraphy of clastic rock was based on brachiopods, corals and fusulinids found in the few limestone beds intercalated with the sandy slate beds. No evidence of sporopollen was found in the gray and dark green clastic rock, which is widely distributed over upper reaches of Taxkorgan River. Early Silurian graptolite fossils: Cf. Climacograptus anjiensis (Yang), Climacograptus cf. minutus Carruthers, cf. Diplograptus deformis Huang and Lu were found in the gray and dark green carbonaceous siltstone, shale at 5 km to the south of Daftar village. Therefore, the age of those strata around Daftar area is in doubt (Wang et al., 2003). 2. Material studied Samples were collected from the gray–black shale intercalated with carbonaceous shale of the Daftar section by Yao Jianxin, Xiao Xuchang, Ji Wenhua and Wang Shiyan (Fig. 1), and were treated chemically by Liu Dengzhou and Zhang Baoping in the laboratory of Institute of Geology, Chinese Academy of Geological Sciences. The sporopollen fossils were studied by Gao Lianda in detail. 3. Permian pollen and spore fossils As a result, the Permian sporopollen: E. punctatus Gao, Wilsonites delicatus (Kosanke) Kosanke, Cordaitina spongiosa (Luber) Samoilovich, Alisporites splendens (Leschik) Foster, Sulcatisporites ovatus (Balme and Hennelly) Balme, Leiotriletes sp. and Punctatisporites sp. were found from the gray–black shale intercalated with carbonaceous shale at 1 km to the south of the Daftar village recently. Because of sulphide pseudomorphs, the preservation of the sporopollen is poor, thus the quality of photographs illustrating is limited (Fig. 2). 4. Discussion about stratigraphic age Above-mentioned Permian sporopollen are widely distributed, except the northern parts of Xinjiang Uygur Autonomous Region and Gansu Province. Among these sporopollen, C. spongiosa was found in the Lower Permian Kungurian of the Russian platform and Urals area as well as the Shangshihezi Formation in Ningwu, northern part of Shanxi Province, China (Gao, 1984; Ouyang and Hou, 1999). W. delicatus, E. punctatus,

68

J. Yao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66–71

Fig. 1. Geographic sketch map of the Dafter, Taxkorgan, Xinjiang Uygur Autonomous Region.

A. splendens and S. ovatus are Permian sporopollen, and occur throughout most of China (except the northern parts of Xinjiang Uygur Autonomous Region and Gansu Province), West Europe and North America. Leiotriletes sp. and Punctatisporites sp. were found in the Xiashi-

hezi Formation in North China (Ouyang and Hou, 1999) and the Maerzheng Formation, in which the Neoschwagerina–Eoplydiexodina Assemblage Zone was found (Jin et al., 2000), in the western end of East Kunlun (Song et al., 2004). The age of the gray–black shale

Fig. 2. The sporopollen fossils from Daftar area, Taxkorgan, Xinjiang Uygur Autonomous Region. (1) Sulcatisporites ovatus (Balme and Hennelly) (Bharadwaj, 1962), X1000, DBD-0-6; (2) (3) Alisporites splendens (Leschik) (Foster, 1979), (2) X700, DBD-0-4, (3) X600, DBD-0-5; (4) Wilsonites delicatus (Kosanke, 1950), X500, DBD-0-1; (5) Cordaitina spongiosa (Luber) (Samoilovich, 1953), X700, DBD-0-3; (6) Endosporites punctatus (Gao, 1984), X700, DBD-0-2.

After Jin et al., 2000; Wen et al., 2000; Song et al., 2004; Gu et al., 2005a,b.

J. Yao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66–71

Table 1 Correlation of Permian strata in West Kunlun Mountains and adjacent areas a

69

70

J. Yao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66–71

intercalated with carbonaceous shale yielding abovementioned Permian sporopollen may belong to Late Cisuralian–Early Lopingian (Table 1). The 276.3 ± 18 Ma the datum (correlation coefficient 0.993) measured for basic volcanic rock at the Hanishanidi of the Daftar area by Ra–Sr isochron dating (Ding et al., 1996) is comparable with the age of turbidity deposits defined by the sporopollen in the Daftar area. The above-mentioned data indicate that the clastic rocks in the upper reaches of Taxkorgan River, especially around Daftar village, may include strata of different ages such as Silurian and Permian etc. Similar cases were also found in the Wenquangou and Jiawendaban areas of West Kunlun (Yao et al., 2004). The Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region (1993) once defined tectonic contacts between Silurian and Permian sections. The authors consider that this opinion conforms to reality for the stratigraphic succession in the upper reaches of the Taxkorganhe River. Based on analysis of the stratigraphy of the orogenic belt, Wang (1996) put forward the basic concept of “non-routine stratigraphy”, examples of which are ancient metamorphic, allochthons, mélanges, ophiolites, olistoliths, seamount rocks and tectonite etc. Mélanges are composed of rocks of the accretional wedge in the inner side of the ocean trench with both oceanic and continental crust rocks intermixed by structural forces, the typical representation of which is the Franciscan complex. Its rock components include turbidite, deepsea sediments, some basic–ultrabasic and land-source blocks. The mixture of Silurian and Permian in the Daftar area is similar to a kind of mélange. It is possible that the Silurian blocks (including strata of other ages) were introduced into the Permian units by structural forces after the Permian, and the mixtite had been formed in the Daftar area. Liu (2001) considered that main tectonic event was the closure of the Paleotethys ocean basin in West Kunlun region during Late Permian and Early Triassic. The Indian plate of south side collided with the Eurasian plate of north side to follow the closure of the Paleotethys ocean basin with the junction belt between the Indian plate and the Eurasian plate long the Kangxiwa fault. Mixtite was formed at that time. Because the data are still limited, it is necessary to test the result by further research on absolute age and the mechanism of the mixtite. Acknowledgements The authors acknowledge the support from the National Nature Science Foundation of China (Grant

40572018) and the Geological Survey of China (Grant 200313000054, 200313000059). The authors thank Mr. Yao She and Mr. Songwei for help during field work in the West Kunlun region, Mr. Liu Dengzhou and Mss. Zhang Baoping for processing the palynology samples. References Bharadwaj, D.C., 1962. The miospore genera in the coals of Raniganj Stage (Upper Permian), India. The Palaeobotanist 9 (1,2), 68–106. Belyaewski, N.A., 1947. Principle characteristics of stratigraphy of the West Kunlun. News of Academy of Sciences, USSR, Series. Geology, vol. 6, pp. 12–30 (in Russian). Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region, 1993. Regional geology of Xinjiang Uygur Autonomous Region. People's Republic of China Ministry of Geology and Mineral Resources, Geological Memoirs, Series 1, Number 32. Geological Publishing House, Beijing, pp. 170–194 (in Chinese, with English abstract). Ding, D., Wang, D., Liu, W., Sun, S., 1996. The Western Kunlun orogenic belt and basin. Geological Publishing House, Beijing, pp. 1–230 (in Chinese, with English abstract). Editorial group of regional stratigraphic chart of Xinjiang Uygur Autonomous Region, 1981. Regional stratigraphic chart of NorthWest China. Fascicle of Xinjiang Uygur Autonomous Region. Geological Publishing House, Beijing, pp. 483–488 (in Chinese). Foster, C.B., 1979. Permian plant microfossils from the Blair Athol coal measures, Baralaba coal measures, and basal Rewan Formation of Queensland. Geological survey of Queensland, Publication 372, Palaeontological Paper 45, pp. 1–244. Gao, L., 1984. Carboniferous and Permian spores and pollen. In: Tianjin Institute of Geology and Ministry Resources (Ed.), Paleontological Atlas of North China, III Micropaleontological Volume. Geological Publishing House, Beijing, pp. 313–340 (Plates 133–164, in Chinese, with English abstract). Gu, F., Feng, S., Zhang, M., 2005a. Permian. In: Centre for Stratigraphy and Palaeontology, China Geological Survey (Ed.), Stratigraphic Division and Correlation of Each Geologic Period in China. Geological Publishing House, Beijing, pp. 277–342 (in Chinese). Gu, F., Feng, S., Zhang, M., 2005b. Permian. In: Wang, Xiaofeng, Chen, Xiaohong (Eds.), Stratigraphic Division and Correlation of Each Geologic Period in China. Geological Publishing House, Beijing, pp. 277–344 (in Chinese). Institute of Geology and Mineral Resources and First Regional Geological Surveying Party, Bureau of Geology and Mineral Resources of Xinjiang, 1991. The Paleozoic Erathem of Xinjiang, No. 2, Stratigraphic Summary of Xinjiang, The second Volume, pp. 329–481. Jiang, C., Yang, J., Feng, B., Zhu, Z., Zhao, M., Cai, Y., Shi, X., Wang, H., Hu, J., 1992. Opening closing tectonics of Kunlun Mountains. People's Republic of China Ministry of Geology and Mineral Resources. Geological Memoirs, vol. 5, 12. Geological Publishing House, Beijing, pp. 31–57 (in Chinese, with English abstract). Jiang, C., Wang, Z., Li, J., et al., 2000. Opening closing tectonics of Central Orogenic Belt. Geological Publishing House, Beijing, pp. 15–18 (in Chinese, with English abstract). Jin, Y., Shang, Q., Hou, J., Li, L., Wang, Y., Zhu, Z., Fei, S., 2000. Dictionary of Stratigraphic terms of China Permian. Geological Publishing House, Beijing, pp. 70–78 (in Chinese).

J. Yao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 66–71 Kosanke, R.M., 1950. Pennsylvanian spores of Illinois and their use in correlation. Illinois State Geological Survey Bulletin 74, 1–128 (16 pls., 2 charts). Liu, X., 2001. Sedimentary–tectonic evolutionary history of the Tianshan to West Kunlun area in West China—the Sedimentary– tectonic evolutionary of the terranes in the corridor of the Xinjiang geotransect and its adjacent areas. Journal of Palaeogeography 3 (3), 21–31 (in Chinese, with English abstract). Ouyang, S., Hou, J., 1999. On characteristics of the Cathaysian palynoflora. Acta Palaeontologica Sinica 38 (3), 261–290 (in Chinese, with English abstract). Samoilovich, S.R., 1953. Pollen and spores from the Permian deposits of the Cherdyn and Aktubinsk areas, Cis-Urals. Trudy Vses Nauchno-issled. Geol. razve. Inst. (VSEGEI) n. s. 75, Palaeobotanist, sb. 5–57 (in Russian). Second Geological team of Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region, 1985. Stratigraphy. Synopsis of geological map and mineral map of the western part of South Xinjiang Uygur Autonomous Region (1:500000), 1, 14–250 (in Chinese). Song, T., Yin, L., Ouyang, S., Wang, B., Wang, J., Ye, Z., Song, S., 2004. Discovery of the Permian palynomorph fossils in the Bukedaban peak area at the western end of Eastern Kunlun Mountain and its geological significance. Journal of Stratigraphy 28 (2), 142–147 (in Chinese, with English abstract). Wang, N., 1996. TBO stratotypes system and non-Smith stratigraphy. In: Wang, Naiwen, Xiang, Liwen (Eds.), Scientific Papers on Geology for International Exchange-Prepared for the 32nd

71

International Geological Congress, Vol. 11, (Chinese). Geological Publishing House, Beijing, pp. 18–26 (in Chinese). Wang, S., Yao, J., Xiao, X., Ji, W., 2003. Discovery of a Silurian graptolite fauna at Daftar Taxkorgan County, Xinjiang. Geological Bulletin of the Geological Survey of China 22 (10), 839–840 (in Chinese, with English abstract). Wen, S., Sun, D., Jin, J., Chen, T., Luo, H., 2000. Stratigraphy. In: Scientific Expedition team to Qinghai-Xizang Plateau of Chinese Academy of Sciences (Ed.), Geological Evolution of the Karakorun–Kunlun Mountains. Beijing Science Press, pp. 6–92 (in Chinese). Yao, J., Xiao, X., Gao, L., Han, F., Cui, J., Peng, H., Ji, Z., Wu, G., 2004. New discovery of sporopollen of the Permian Jiawendaban Formation in the West Kunlun–Kalakunlun area. Geological Bulletin of China 23 (5–6), 620–621 (in Chinese with English abstract).

Further reading Ruan, Y., 1995. Carboniferous, Permian stratigraphy and outline of paleogeography. In: Zhou, Z., Lin, H. (Eds.), Stratigraphy, Paleogeography and Plate Tectonics in Northwest China. University Press, Nanjing Nanjing, pp. 1–299 (in Chinese). Yin, H., 1988. Paleobiogeography of China. China University of Geosciences Press, pp. 176–197 (in Chinese, with English abstract).