Geology and biostratigraphy of the Jurassic and lower cretaceous series to the north of the Lhasa Block (Tibet,China) |
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| Authors: | Jean Marcoux Jacques Girardeau Eric Fourcade Jean-Paul Bassoullet Jean Philip Michel Jaffrezo |
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| Institution: | 1. Sciences Physiques de la Terre, Université Paris 7, 2 Place Jussieu, F 75250, Paris cedex 05, France.;2. Laboratoire de Pétrologic Physique, IPGP et, Université Paris 7,, 2 Place Jussieu, F 75250 Paris cedex 05 France.;3. CNRS, Laboratoire de Stratigraphie, VA 319, Université Paris 6, F 75252 Paris France.;4. Laboratoire de Géologie Stratigraphique et Structurale, Université de Poitiers, 86022 Poitiers France.;5. Laboratoire de Stratigraphie, Faculté des Sciences Saint-Jérome, 13397 Marseille,, France. |
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| Abstract: | Abstract— The Lhasa Block (s.l.) is bounded to the South by the Tertiary Yarlung Zangbo suture zone and to the North by the terminal Jurassic/earliest Cretaceous Bangong Nu Jiang suture zone. Several tectonostratigraphic units have been recognized in the central-northern part of the Lhasa Block. These are from bottom to top : 1) a thick turbiditic series with a few lenses of allodapic limestones which have yielded an Aalenian — Bajocian foraminiferal assemblage. This series is tectonieally overlain by the Donqiao ophiolite; 2) the continental to shallow marine late Malm to lowermost Cretaceous Zigetang Formation which disconformably overlies the Donqiao ophiolite and 3) continental red detrital rocks or marine Early/Late Aptian boundary to Early Albian foraminifera-rich bedded limestones in which some volcanic rocks are locally interbedded.We discuss the palaeogeographical distribution and biostratigraphical meaning of some foraminifera (Gutnicella cayeuxi (LUCAS), Palorbitolina fen<ícu/o?(Bl .LMKNBACIl), Praeorbitolina cormyi SCHROEDER and Palor-bilolmoides hedini CHREREHI and ScilKOKDK.lt) and their bearing on the radiometric age of the Aptian-Albian boundary. |
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| Keywords: | Regional geology Biostratigraphy Jurassic Cretaceous Tibet |
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