U-Pb detrital zircon geochronology of sedimentary rocks in NE Vietnam: Implication for Early and Middle Devoni-an Palaeogeography

Rocks of the Do Son Peninsula in NE Vietnam are mainly composed of Paleozoic siliciclastics. The overall sedimentary record represents fluvial to deltaic prograding deposits close to a shoreline. We present detrital zircon U-Pb analytical results from two samples, the Van Canh and the Van Huong Formations (east Red River Basin). Zircons were analyzed for U, Th, and Pb isotopes by LA-SF ICP-MS techniques. The youngest zircon of each formation provides maximum ages of sedimentation at 407.1 ± 9.5 Ma and 406.3 ± 4.0 Ma. The zircon cluster of both samples supports the postulated position of NE Vietnam close to the western Himalaya.ReferencesAnh H.T.H., Hieu P.T., Le Tu V., Choi S.H. and Yu Y., 2015. Age and tectonic implications of Paleoproterozoic Deo Khe Granitoids within the Phan Si Pan Zone, Vietnam. Journal of Asian Earth Sciences, 111, 781-791. Braddy S.J., Seldon P.A., Doan Nhat T., 2002. A new carcinosomatid eurypterid from the Upper Silurian of northern Vietnam. Palaeontology, 45, 897-915. Burrett C., 1974. Plate tectonics and the fusion of Asia. Earth and Planetary Science Letters, 21, 181-189. Burrett C. and Stait B., 1985. South East Asia as a part of Ordovician Gondwanaland-a palaeobiogeographic test of a tectonic hypothesis. Earth and Planetary Science Letters, 75, 184-190. Burrett C. and Stait B., 1987. China and Southeast Asia as part of the Tethyan margin of Cambro-Ordovician Gondwanaland. In: McKenzie, K. (Ed.), Shallow Tethys, 2. Balkema, Rotterdam, 65-77. Burrett C., Long J. and Stait B., 1990. Early-Middle Palaeozoic biogeography of Asian terranes derived from Gondwana. In: McKerrow, W., Scotese, C. (Eds.), Palaeozoic Palaeogeography and Biogeography. Geological Society Memoir, 12, 163-174. Burrett C., Duhig N., Berry R. and Varne R., 1991. Asian and south-western Pacific continental terranes derived from Gondwana and their biogeographic significance. Australian Systematic Botany, 4, 13-24. Burrett C., Zaw K., Meffre S., Lai C.K., Khositanont S., Chaodumrong P., Udchachon M., Ekins S. and Halpin J., 2014. The Configuration of Greater Gondwana - Evidence from LA ICPMS, U-Pb geochronology of detrital zircons from the Palaeozoic and Mesozoic of Southeast Asia and China. Gondwana Research, 26, 31-51. http://dx.doi.org/10.1016/j.gr.2013.05.020. Condie K., Belousova E., Griffin W. and Sircombe K., 2009. Granitoid events in space and time: constraints from igneous and detrital zircon age spectra. Gondwana Research, 15, 228-242. http://dx.doi.org/10.1016/j.gr2008.06.001. Faure M., Lepvier C., Nguyen V.V., Vu T.V., Lin W. and Chen Z., 2014. The South China block-Indochina collision: Where, when, and how? Journal of Asian Earth Sciences, 79, 260-274. Findlay R.H., 1997 The Song Ma anticlinorium, northern Vietnam: the structure of an allochthonous terrane containing an early Paleozoic island arc sequence. Journal of Asian Earth Sciences, 15, 453-464. Gerdes A. and Zeh A., 2006. Combined U-Pb and Hf isotope LA-(MC-) ICP-MS analysis of detrital zircons: comparison with SHRIMP and new constraints for the provenance and age of an Armorican metasediment in Central Germany. Earth and Planetary Science Letters, 249, 47-61. Hall R., 2009. The Eurasia SE Asian margin as a modern example of an accretionary orogen. In: Cawood, P.A., Kroner, A. (Eds.), Earth Accretionary Systems in Space and Time. The Geological Society London, Special Publications, 318, 351-372. Helmcke D., 1985. The Permo-Triassic “Paleotethys” in mainland Southeast Asia and adjacent parts of China. Geologische Rundschau, 74, 215-228. Hieu P.T., Chen F., Me L.T., Thuy N.T.B., Siebel W. and Lan T.G., 2012. Zircon U-Pb ages and Hf isotopic compositions from the Sin Quyen Formation: the Precambrian crustal evolution of northwest Vietnam. International Geology Review, 54(13), 1548-1561. Hieu P.T., Dung N.T., Thuy N.T.B., Minh N.T. and Pham M.I.N.H., 2016. U=Pb ages and Hf isotopic composition of zircon and bulk rock geochemistry of the Dai Loc granitoid complex in Kontum massif: Implications for early Paleozoic crustal evolution in Central Vietnam. Journal of Mineralogical and Petrological Sciences, 111(5), 326-336. Horstwood M.S.A., Košler J., Gehrels G., Jackson S.E., McLean N.M., Paton C., Pearson N.J., Sircombe K., Sylvester P., Vermeesch P., Bowring J.F., Condon D.J. and Schoene, B., 2016. Community-derived standards for LA-ICP-MS U-Th-Pb geochronology - uncertainty propagation, age interpretation and data reporting. Geostand Geoanalytical Research, 40, 311-332. Jackson S., Pearson N.J., Griffin W.L. and Belousova E.A., 2004. The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology. Chemical Geology, 211, 47-69. Janvier P., Blieck A., Gerrienne P. and Tong-Dzuy T., 1987. Faune et flore de la Formation de Sika (Devonien inferieur) dans la peninsule de Do Son (Viet Nam). Bulletin du Museum National d’Histoire Naturelle Paris, 9, 291-301. Janvier P., Racheboeuf P., Nguyen Huu H. and Doan Nhat T., 2003. Devonian fish (Placodermi, Antiarcha) from the Tra Ban Island (Bai Tu Long Bay, Quang Ninh, Vietnam) and the question of the age of the Do Son Formation. Journal of Asian Earth Sciences, 21, 795-801. Janvier P. and Ta Hoa P., 1999. Les Vertebres (Placodermi, Galeaspida) du Devonien inferieur de la coupe de Lung Co-Mia Le, province de Ha Giang. Vietnam, avec des donnees complementaires sur les gisements a Vertebres du Devonien du Bac Bo oriental. Geodiversitas, 21, 33-67. Janvier P. and Tong-Dzuy T., 1998. The Silurian and Devonian vertebrates of Vietnam: a review. Journal of Geology (Hanoi), B11, 12, 18-28. Jones N.S., Fyfe J.A., Sewell R.T., Lai K.W. and Lee C.M., 1997. Devonian fluviodeltaic sedimentation in Hong Kong. Journal of Asian Earth Sciences, 15(6), 533-545. Komatsu T., Kato S., Hirata K., Takashima R., Orata Y., Oba M., Naruse H., Tha Hoa P., Nguyen P.D., Dang H.T., Doan T.N., Nguyen H.H., Sakata S., Kaiho K. and Königshof P., 2014. Devonian-Carboniferous transition containing a Hangenberg Black Shale equivalent in the Pho Han Formation on Cat Ba Island, northeastern Vietnam. Palaeogeography, Palaeoclimatology, Palaeoecology, 404, 30-43. http://www.doi: 10.1016/j.palaeo.2014.03.021. Königshof P., Narkiewicz K., Phuong Ta Hoa, Carmichael S. and Waters J., 2017. Events in the mid- Paleozoic: Examples from the eastern Paleotethys (Si Phai section, NE Vietnam). In: Mottequin B., Slavik L., Königshof P. (eds.) Climate change and biodiversity patterns in the mid-Palaeozoic - Proceedings-Volume IGCP 596/SDS Meeting Brussels (2015). Palaeobiodiversity and Palaeoenvironments, 97(3), 481-496. http://www.doi.10.1007/s12549-017-0272-5. Lantenois H., 1907. Note sur la Géologie de l’Indochine. Mémoires de la Société Géologique de France, 4, 1-56. Lee C.M., 1991. The discovery of Devonian Placodermi in Hong Kong and its significance. In: Chang M.M., Liu Y.H., Zhang G.R. (Eds.). Early Vertebrates and Related Problems of Evolutionary Biology. Science Press, Beijing, 131-138. Lepvrier C., Faure M., Nguyen Van V., Van Vu T., Lin W., Ta Trong T. and Ta Hoa P., 2011. North-directed Triassic nappes in Northeastern Vietnam (East Bac Bo). Journal of Asian Earth Sciences, 41, 56-68. Long J.A., Burrett C., Pham Kim N. and Janvier P., 1990. A new bothriolepid antiarch (Pisces, Placodermi) from the Devonian of Do Son Peninsula, northern Vietnam. Alcheringa, 14, 181-194. Ludwig K.R., 2001. Users Manual for Isoplot/Ex rev. 2.49: Berkeley Geochronology Center Special Publication, No.1a, 1-56. Metcalfe I., 1984. Stratigraphy, palaeontology and palaeogeography of the Carboniferous of Southeast Asia. Mémoires Société Géologiques France (New Series), 147, 107-118. Metcalfe I., 1998. Palaeozoic and Mesozoic geological evolution of the SE Asian region: multidisziplinary constraints and implications for biogeography. In: Hall R., Holloway J.D. (Eds.), Biogeography and Geological Evolution of SE Asia. Backhuys Publishers, Leiden, The Netherlands, 25-41. Metcalfe I., 2006. Palaeozoic and Mesozoic tectonic evolution and Palaeogeography of East Asian crustal fragments: the Korean Penninsula in context. Gondwanan Research, 9, 24-46. Metcalfe I., 2011. Tectonic framework and Phanerozoic evolution of Sundaland. Gondwana Research, 19, 3-21. http://dx.doi.org/10.1016/j.gr.2010.02.016. Morley C.K., Ampaiwan P., Thanudamrong S., Kuenphan N. and Warren J., 2013. Development of the Khao Kwang Fold and thrust belt: implications for the geodynamic setting of Thailand and Cambodia during the Indosinian Orogeny. Journal of Asian Earth Sciences, 62, 705-719. http://dx.doi.org/10.1016/j.seaes.2012.11.021. My Dung Tran, Junlai L.I.U., Xiaochun L.I. and My Cung Dang., 2016. Geology, Fluid Inclusion and Isotopic Study of the Neoproterozoic Suoi Thau Copper Deposit, Northwest Vietnam. Acta Geologica Sinica (English Edition), 90(3), 913-927. Nagy E.A., Maluski H., Lepvrier Q., Scharer U., Thi P.T. and Leyreloup A., 2001. Geodynamic significance of the Kontum Massif in Central Vietnam: Composite 40Ar-39Ar and U/Pb ages from the Palaeozoic to Triassic. Journal of Geology, 109, 755-770. Nam T.N., 1995. The Geology of Vietnam: A brief summary and problems. Geoscientific Reports, Shizuoka University, 1-10. Nam T.N., Toriumi M., Sano Y., Terada K. and Thang T.T., 2003. 2.9, 2.36, and 1.96 Ga zircons in orthogneiss south of the Red River shear zone in Viet Nam: evidence from SHRIMP U-Pb dating and tectonothermal implications. Journal of Asian Earth Sciences, 21(7), 743-753. Nguyen T.T.B., Hieu P.T., Hai T.T., Xuan N.T. and Cung D.M., 2014. Petrogenesis and zircon U-Pb ages of the Thien Ke granitic pluton in the Tam Dao region: Implications for early Paleozoic tectonic evolution in NE Vietnam. Journal of Mineralogical and Petrological Sciences, 109(5), 209-221. Nie Y.S., 1991. Paleoclimate and paleomagnetic constraints on the Paleozoic reconstructions of South China, North China and Tarim. Tectonophysics, 196, 279-309. Ogg J.G., Ogg G.M. and Gradstein F.M., 2016. A concise geologic time scale. Elsevier: 1-234. Racheboeuf P.R., Janvier P., Ta Hoa P., Vannier J. and Wang S.-Q., 2005. Lower Devonian vertebrates, arthropods and brachiopods from northern Vietnam. Geobios, 38, 533-551. Roger F., Leloup P.H., Jolivet M., Lacassin R., Trinh P.T., Brunel M. and Seward D., 2000. Long and complex thermal history of the Song Chay metamorphic dome (Northern Vietnam) by multi-system geochronology. Tectonophysics, 321, 449-466. Sengör A.M.C., Altiner D., Cin A., Ustaomer T. and Hsu K.J., 1988. Origin and assembly of the Tethyside orogenic collage at the expense of Gondwana Land. In: Audley Charles, M.G., Hallam, A. (Eds.), Gondwana and Tethys. Geological Society of London, Special Publications, 37, 119-181. Sircombe K.N., 2004. AGE DISPLAY: an EXCEL workbook to evaluate and display univariate geochronological data using binned frequency histograms and probability density distributions. Computers Geosciences, 30, 21-31. Sláma J., Košler J., Condon D.J., Crowley J.L., Gerdes A., Hanchar J.M., Horstwood M.S.A., Morris G.A., Nasdala L., Norberg N., Schaltegger U., Schoene B., Tubrett M.N. and  Whitehouse M.J., 2008. Plešovice zircon - A new natural reference material for U-Pb and Hf isotopic microanalysis. Chemical Geology, 249, 1-35. Sone M. and Metcalfe I., 2008. Parallel Tethyan sutures in mainland Southeast Asia: new insights for the Palaeo-Tethys closure and implications for the Indosinian Orogeny. Comptes Rendu Geoscience, 340, 166-179. http://dx.doi.org/10.1016/j.crte.2007.09.008. Squire R., Campbell I., Allen C. and Wilson C., 2006. Did the Transgondwanan Supermountain trigger the explosive radiation of animals on Earth? Earth and Planetary Sciences Letters, 250, 116-133. Stacey J.S. and Kramers J.D., 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters, 26, 207-221. Tapponnier P., Lacassin R., Leloup P.H., Scharer U., Zhong D., Wu H., Liu X., Ji S., Zhang L. and Zhong J., 1990. The Ailao Shan - Red River metamorphic belt: Tertiary left lateral shear between Sundaland and South China. Nature, 343, 431-437. Tong-Dzuy, T. (Ed.), 1986. The Devonian of Vietnam. Science and Technics Publishing House, Hanoi, 141p (in Vietnamese).Tong-Dzuy T., Janvier P., Doan Nhat T. and Braddy S., 1994. New vertebrate remains associated with eu-rypterids from the Devonian Do Son Formation. logy (Vietnamese), Hanoi, A, 224, 1-11. Torsvik T. and Cocks R., 2009. The Lower Palaeozoic palaeogeographical evolution of the northeastern and eastern peri-Gondwanan margin from Turkey to New Zealand. In: Bassett, M. (Ed.), Early Palaeozoic Peri-Gondwana Terranes: New Insights from Tectonics and Biogeography. Geological Society, London Special Publications, 325, 3-21. http://dx.doi.org/10.1144/SP325.2 0305-8719/09/. Tri T.V. and Khuc V. (Eds.), 2011. Geology and Earth Resources of Viet Nam. Ministry of Nature Resources and Environment. General Department of Geology and Minerals of Vietnam, 634p. Ueno K. and Charoentitirat T., 2011. Carboniferous and Permian. In: Ridd M., Barber A., Crow M. (Eds.), The Geology of Thailand. Geological Society, London, 71-136. Usuki T., Lan C.-Y., Wang K-L. and Chiu H.-Y., 2013. Linking the Indochina block and Gondwana during the Early Paleozoic: Evidence from U-Pb ages and Hf isotopes of detrital zircons. Tectonophysics, 586, 145-159. Vu Van Tich, 2001. Petrologie et Geochronologie Ar-Ar du Bloc de Kontum (Vietnam). DEA University, Montpelier, p40. Wan Y., Liu D., Wang W., Song T., Kroner A., Dong C., Zhou H. and Yin X., 2011. Provenance of Meso-Neo Proteroizoic cover sediments at the Ming Tombs, Beijing, North China Craton: an integrated study of U-Pb dating and Hf isotopic measurement of detrital zircons and whole rock geochemistry. Gondwana Research, 20, 219-242. http://dx.doi.org/1016/j.gr.2011.02.009. Xun Z., Allen M.B., Whitham A.G. and Price S.P., 1996. Rift-related Devonian sedimentation and basin development in South China. Journal of Southeast Asian Earth Sciences, 14(1/2), 37-52. Yan D.P., Zhou M.F. and Wang Y.C., 2006. Structural and geochronological constraints on the Dulong-Song Chay tectonic dome in SE Yunnan (SW China) and northern Vietnam. Journal of Asian Earth Sciences, 28, 332-353. Yang S.P., Pan K., and Hou H.F., 1981. The Devonian System in China. Geological magazine, 118(2), 113-224. Yu J.H., Wang L.J., O`Reilly S.Y., Griffin W.L., Zhang M., Li C.Z. and Shu L.S., 2009. A Paleoproterozoic orogeny recorded in a long-lived cratonic remnant (Wuyishan terrane), eastern Cathaysia Block, China. Precambrian Research, 174, 347-363. Zhao G.C. and Cawood P.A., 2012. Precambrian Geology of China. Precambrian Research, 222(223), 13-54. Zhao X., Allen M.B., Whitham A.G. and Price S.M., 1996. Rift-related Devonian sedimentation and basin development in South China. Journal of Southeast Asian Earth Sciences, 14(1/2), 37-52. Zhu D.C., Zhao Z.D., Niu Y.L., Dilek Y. and Mo X.X., 2011. Lhasa terrane in southern Tibet came from Australia. Geology, 39, 727-730.

Some natural heritages of outstanding values for tourism development in Central Highland

Tay Nguyen or the Central Highland with the remains of Archean relics is known as the region of the oldest natural formation across Vietnam’s territory. Had been taking place in the Central Highland the combined tectonic activities with typical exogenous process of the Cenozoic. Tay Nguyen contains many valuable natural resources, especially natural heritages that facilitate the development of ecotourism and scientific tourism. Scope of the TN3/T18 national project as part of the Central Highland Program 3 mainly covers research on the outstanding values, including 1) Some areas of extraordinary beauty and aesthetic value such as Dray Nur and Dray Sap waterfalls on the Serepok River in Dak Lak and Dak Nong provinces. 2) Fossil of the yews discovered in the Chu A Thai mountain, Phu Thien district, Gia Lai province; 3) Typical “living fossil plants” of the Central Highland that still exist such as yews (Glyptostrobus pensilis) and two flat-leaf pine-trees (Ducampopinus krempfii) in Gia Lai and Lam Dong; 4) Stone of the Kan Nack series (NA-PP) that is one of the oldest nationwide in basins of the Ba river, Gia Lai province; 5) Spectacular volcano landscape in Gia Lai and Kon Tum; 6) The unique cave system in the Krong No area, formed in basalt layer, is of fundamental difference from Vietnam’s popular limestone caves.ReferencesBonface B. G., Cooper C., 2012: Worldwide Destinations: The Geography of Travel and Tourism, Publishing House Routledge, p.610. Võ Văn Chi. 2004: Từ điển Thực vật thông dụng (Tập 2). Nxb. Khoa học và Kỹ thuật, Hà Nội, 2698tr. La Thế Phúc, Trương Quang Quý, Đỗ Chí Kiên, 2010: Di sản địa chất liên quan đến đá basalt ở Tây Nguyên và các giải pháp bảo tồn phát triển bền vững. Số đặc biệt kỷ niệm 65 năm ngày truyền thống ngành Địa chất Việt Nam. TC Địa chất. Hà Nội, 320, 514-521. La Thế Phúc, Lương Thị Tuất, Trương Quang Quý, 2012: Hang động trong đá basalt ở Cư Jut, Đắk Nông, Việt Nam. Hội nghị Công viên Địa chất Toàn cầu năm 2012 tại Unzen, Nhật Bản, tháng 5/2012. Nguyễn Thành Mến, 2013: Một số đặc điểm quần thể và phân bố loài Thông hai lá dẹt (Pinus krempfii H. Lec) ở Lâm Đồng. Tạp chí Khoa học Lâm nghiệp số 1, năm 2012, tr.2095-2104. Trương Quang Quý, La Thế Phúc, 2010: Trinh Nữ waterfall geologicall heritage, Đắk Nông province. Journal of Geology; series B.35-36/2010; 131-139. Hà Nội: Department of Geology and Minerals of Vietnam. H. Tachihara, TS. T. Honda, 2014: Báo cáo kết quả nghiên cứu sơ bộ các hang động núi lửa ở Đắk Nông, Việt Nam. Hội nghị Thông cáo báo chí “Công bố kết quả khảo sát hang động núi lửa tại khu vực Krông Nô, tỉnh Đắk Nông, Tây Nguyên Việt Nam” ngày 26/12/2014 tại Tổng cục Địa chất và Khoáng sản Việt Nam, số 6 Phạm Ngũ Lão, Hà Nội. Tong Dzuy Thanh, Vu Khuc (Editors), et al., 2006: Stratigraphical units of Vietnam. Vietnam National University Publishing House. Hanoi. 528 pgs. (2012 in lần thứ 2). Trần Văn Trị, Vũ Khúc (Editors) và nnk. 2012: Geology and Earth Resources of Vietnam. Publishing House for Science and Technology, Hanoi. 636 pgs. Wolfgang Eder, 2004: Geoparks - geological attractions: A tool for public education, recreation and sustainable economic development. UNESCO, Division of Earth Sciences, 1, rue Miollis, F-75732 Paris Cedex 15, France.

Effects of combined rice flour and molasses use on the growth performance of Pacific white shrimp (<em>Litopenaeus vannamei</em> Boone, 1931) applied biofloc technology

A 63-day completely random experiment with three replications was carried out to compare the effects of five different combination ratios of rice flour (R) and molasses (M) on the growth and survival rates of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) postlarvae applied biofloc technology. Five biofloc (BF) treatments, including R90-M10, R70-M30, R50-M50, R30-M70, and R10-M90, formed with the addition of different combination ratios of rice flour and molasses, i.e., 90% R+10% M, 70% R+30% M, 50% R+50% M, 30% R+70% M, and 10% R+90% M, respectively, with C/N ratios of 15:1, and a control (neither rice flour nor molasses applied) was randomly arranged into the 18 plastic tanks of 1.0 m3 volume (with 0.5 m3 of water) each tank and salinity of 15‰. The postlarvae (0.095 g) were stocked into the tanks at a 150 ind. m−3 density and fed pelleted feed (40% protein). There was an improvement in growth (FMW, WG, DWG, and SGR) for all treatments. Besides, treatments with more than or equal to 30% molasses have improved SR, FCR, and FB. Especially the highest SR (94.2%) was obtained at the R70-M30, which perhaps created the highest FB (1.435 kg m−3) in this treatment. The lowest FCR (1.28) was also observed in the R70-M30 and significantly differed from the control and other treatments. Besides, water quality parameters were within the ranges recommended for Pacific white shrimp health during the experimental period. Our findings indicated the benefits of shrimp culture using the BF system when different combined ratios of rice flour and molasses were applied, of which a ratio of 70% rice flour and 30% molasses was considered as the best

Expanding HIV Testing Efforts in Concentrated Epidemic Settings: A Population-Based Survey from Rural Vietnam

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Les vert\ue9br\ue9s (Placodermi, Galeaspida) du D\ue9vonien inf\ue9rieur de la coupe de Lung C\uf4-Mia L\ue9, Province de H\ue0 Giang, Vi\ueat Nam, avec des donn\ue9es compl\ue9mentaires sur les gisements \ue0 vert\ue9br\ue9s du D\ue9vonien du Bac Bo oriental

Volume: 21Start Page: 33End Page: 6

Les vertébrés (Placodermi, Galeaspida) du Dévonien inférieur de la coupe de Lung Cô-Mia Lé, Province de Hà Giang, Viêt Nam, avec des données complémentaires sur les gisements à vertébrés du Dévonien du Bac Bo oriental

Les vertébrés des formations de Si Ka, Bac Bun et Mia Lé (Dévonien inférieur, Lochkovien-Praguien) de la coupe Lung Cô-Mia Lé (province de Hà Giang, nord du Viêt Nam) sont représentés par quelques restes de galéaspides, d\u27antiarches, d\u27arthrodires et par un pétalichthyide nouveau, Tongdzuylepis vietnamensi n.g., n.sp. La liste faunique de la Formation de Khao Lôc (Lochkovien inférieur) à Tòng Vài (province de Hà Giang) est complétée par la description d\u27un galéaspide, Laxaspis yulongssus, et de trois antiarches Heteroyunnanolepis qujingensis, Zhanjilepis aspratilis et Minicrania lissa n.sp. Un nouvel antiarche, Yunnanolepis spinulosa n.sp., associé à du matériel de Chuchinolepis dongmoensis et Youngolepis sp. est décrit dans des niveaux de la limite entre les formations de Si Ka et Bac Bun du gisement de Ban Nhuân (province de Thái Nguyên, nord du Viêt Nam). Une description complémentaire et des précisions taxonomiques sont apportées quant aux galéaspides et antiarches de la Formation de Bac Bun du gisement de Dông Mo (province de Lang Son, nord du Viêt Nam). Enfin, un nouveau sarcoptérygien, Langdenia campylognatha n.sp. est décrit dans la Formation de Bac Bun du gisement de Trang Xa (province de Thái Nguyên).The vertebrates of the Si Ka, Bac Bun and Mia Lé formations (Lower Devonian, Lochkovian-Pragian) of the Lung Cô-Mia Lé section (Hà Giang Province, northern Vietnam) are represented by some galeaspid, arthrodire and antiarch remains, and by a new petalichthyid, Tongdzuylepis vietnamensis n.g., n.sp. The faunal list of the Khao Lôc Formation (Lower Lochkovian) at Tòng Vài (Hà Giang Province) is completed by the description of a galeaspid, Laxaspis yulongssus, and three antiarchs, Heteroyunnanolepis qujingensis, Zhanjilepis aspratilis and Minicrania lissa n.sp. A new antiarch, Yunnanolepis spinulosa n.sp., associated with Chuchinolepis dongmoensis and Youngolepis sp., is described from the transition beds between the Si Ka and Bac Bun formations at Ban Nhuân (Thái Nguyên Province, northern Vietnam). A complementary description and taxonomic comments are made for the galeaspids and antiarchs of the Bac Bun Formation at Dông Mo (Lang Son Province, northern Vietnam). Finally, a new sarcopterygian, Langdenia campylognatha n.sp. is described from the Bac Bun Formation at Trang Xa (Thái Nguyên Province).</p

North-directed Triassic nappes in Northeastern Vietnam (East Bac Bo)

International audienceA careful re-examination of the previous tectonic descriptions and the acquisition of new structural and kinematic data have been undertaken in northeastern Vietnam. The structure of the area consists of a system of slightly metamorphosed but ductilely deformed nappes, including recumbent folds, formed during the Triassic, prior to the unconformable deposition of the Upper Triassic terrigenous sediments. These results confirm the previous interpretation of " preyunnanaises nappes ", represented by Middle-Upper Paleozoic foliated limestone resting through a flat mylonitic contact over an intermediate " Song Mien unit " (Deprat, 1915), the latter made essentially of deformed Lower Triassic sedimentary and volcanic formations, which previously filled the Song Hien rift (Bourret, 1922). In the external part of the belt, the Triassic strata conformably overlie slightly deformed and unmetamorphosed Upper Paleozoic rocks, forming an autochthonous domain. Alternatively, the same Triassic succession can be seen resting tectonically through décollement zones, directly over the Middle Paleozoic marbles, to form a distinct but subsidiary allochthonous unit. Our data show that the Song Chay orthogneiss and its Lower Paleozoic sedimentary country rocks belong to the main nappe. They also demonstrate that this nappe was transported to the N-NE. A newly discovered ophiolitic mélange of supposed oceanic nature and Triassic age, lying along the Song Chay Fault, North of the Nui Con Voi, could hypothetically represent the rooted zone of the nappe. A Tertiary overprinting event, in particular accommodated by strike-slip movements, likely accounts for the present orocline of NE Vietnam

A new Early Devonian galeaspid from Bac Thai Province, Vietnam

Volume: 36Start Page: 297End Page: 30

Facies, magnetic susceptibility and timing of the Late Devonian Frasnian/Famennian boundary interval (Xom Nha Formation, Central Vietnam)

Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xom Nha Formation, Central Vietnam, were studied. The section is mainly composed of fossiliferous, brecciated, and laminated limestone beds, while shale beds occur in a subordinate number. Microfacies generally suggests a hemipelagic setting on an outer shelf environment with low sedimentation rates. A sediment accumulation rate of 0.217 cm/kyrs for this section is calculated. The Xom Nha section does not exhibit characteristic black shales or black limestones through the F/F boundary, but instead shows a similar lithology in comparison to other F/F sections in Southeast Asia. The carbonates yielded abundant conodonts, which represent mainly cosmopolitan species but the section differs from most sections in Europe in showing relatively high numbers of Palmatolepis linguiformis species. Deposition through the F/F boundary interval reported here for the Xom Nha section appears to have occurred during a ~1.2 Ma, and shows well-defined climate cyclicity.NAFOSTEDGerman Science FoundationProject for Collecting Paleontological Specimens in Vietna