| 西藏南部古错侏罗—白垩系界线剖面的新观察 |
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| 引用本文：姚培毅,刘训,傅德荣.1990.西藏南部古错侏罗—白垩系界线剖面的新观察[J].地球学报,11(2):41-54. |
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| 全文下载次数: 2005 |
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| 中文摘要:我国西藏南部聂拉木古错剖面是我国目前研究海相侏罗—白垩系界线较为理想的剖面之一。本文论述了这条剖面上的双壳类、菊石的特征以及沉积环境特点,划分出2个双壳类动物群,从一个新的角度为进一步研究侏罗—白垩系界线提供了有关的证据。 |
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| NEW OBSERVATION ON THE JURASSIC-CRETACEOUS BOUNDARY SECTION AT GUCUO,NYALAM,XIZANG |
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| Abstract:This set of the Jurassic-Cretaceous boundary section is situated at a-hill west of Gucuo, extending for approximately 3km Irom the place 300m west of Gucuo village, Nyalam county to the south. This section is one of the best sections in China for marine Jurassic-Cretaceous boundary study. It is well-exposed with successive deposition and simple structure, containing abundant ammonites, bivalves, scaphopods and microfossils across the boundary.In 1988 the authors mainly examined Jurassic-Cretaceous boundary of Gucou section and collected abundant bivalve, ammonites, microfossil and other specimens from the Gucuo Ⅰ Formetion and the Gucuo Ⅱ Formation.Ⅰ. Geological section of the Jurassic-Cretaceous boundary at GucuoAccording to Liu Guitang, Wang Sien's study of ammonites and strata,. Gucuo section is divided into 6 formations in ascending orders as follows: the Menkatun Formation (Middle-Upper Tithonian), the Gucuo Ⅰ Formation (The most top of upper Tithonian), the Gucuo Ⅱ Formation (Berriasian), the Gucuo Ⅲ Formation (Valanginian-Hauterivian), the Gucuo Ⅳ Formation (Barremian), the Gucuo Ⅴ Formation (Aptian-Albian).The geological section range from north to south with their stratigra-the phic sequence overturned or nearly vertical (Fig. 1).Gucuo Ⅲ Formation (Valanginian-Hauterivian) 11. light gray quartz sandstone intercalated with 2m siltyshale and fine grain sandstone. 6m thick10. grayish yellow, grayish green fine grain sandstone with cross-bedding, upward to becoming grayish black silty shales intercalated with thin bedded fine grain sandstone, yielding ammonites: Thurmanniceras jenkinsi( Anderson), Th. cf. stippi (Anderson). 51.5m thick-- conformable contact--the Gucuo Ⅱ Formation (Berriasian)9. grayish black muddy siltstone, silty shales intercalated with fine grain sandstone with calcareous nodules, yielding ammonites: Neocomites sp., Berriasella sp.; bivalves; Entolium sp. 143.2m thick 8. grayish white, grayish black sheet shales intercalated with marl, yielding ammonites: Berriasella cf. grandis Mazenot, B. cf. berthei Mazenot, Neocomites sp.; Bivalves: Neilo biplicata Yao, N. elongata Yao, Mesosaccella simplex Yao, Nuculana (Praesaccella) ovata Yao, Gramm-atodon (Lamellelodon) gucuoensis Yao, G. (L. ) ingenitis Yao. Entolium protentum Yao, E. altilis Yao, E. delina-tum Yao, Psendolimea gaultina (Woods), P. elegans Yao, P. solida Yao, P. globata Yao, Astarte elongata d'Orbi-gny, A. elata Yao, Eotrigonia tibetensis Yao; scaphop-ods: Dentalium jeffereysi Gardner, D. gucuoensis Yao. 34.4m thick-- conformable contact--the Gucuo Ⅰ Formation (The most top of upper Tithonian) 7. grayish yellow, yellowish green find grain sandstones interbedded with grayish black, grayish green silty shales with calcareous nodules, yielding ammonites: ?Corongoceras sp.; bivalves: Nuculana (Praesaccella) juriana Cox, Meleagrinella echinata (W. Smith). 101.4m thick 6. grayish green shales intercalated with thin bedding fine grain sandstone and marl, yielding bivalves: Palaeonuc-ula triangularis Duff, Pleuromya spitiensis Holdhaus.18.6m thick5. grayish silty shales intercalated with grayish yellowsiltstone with lime nodules. 20.9m thick4. deep grayish green middle-fine grain sandstone intercalated with middle-thick sandstone with ripple makings and trace fossils. 44.6m thick3. grayish green, grayish yellow, grayish black sandy shale intercalated with thin bedding fine grain sandstone with cross bedding, yielding bivalves: Palaeonucula calliope (d'Orbiny), P. kaoraensis Cox, Pinna sp., Entolium of. nieniexionglaense Wen, Camptonectes (C. ) auritus(Schlo-thein), Meleagrinella nieniexionglaensis Wen, M. copiosa Yao, Plagiostoma cf. aciculata Mumber, Limatula gibbosa (Sowerby), Sinopsammobia gucuoensis Yao, Protocardia africana Cox. |
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