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Dispersal events of Triassic-Jurassic boundary faunas, and paleoenvironment of Tibetan Himalaya

Science China Earth Sciences 2009年第12期52卷 1993-2000页

作者： YIN JiaRun fü rsich franz theodor School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China Geozentrum Nordbayern Friedrich-Alexander Universitat ErlangenLoewenichstr.28D-91054ErlangenGermany

End-Triassic ammonoid and bivalve faunas of the Germig area, Tibetan Himalaya, lived in a tropical, shallow-water environment during the Triassic-Jurassic boundary interval. High stratigraphic resolution based on ammonite-biochrons allows to tracing the place of origin of several faunal elements. The bivalves Aguilerella and Ctenostreon occurred first in the Tibetan Himalaya and migrated from there to the eastern South Pacific, exhibiting a pantropic dispersal pattern. This dispersal route is supported by the distribution pattern of the ammonites Choristoceras, Discamphiceras, Pleuroacanthites, and Psiloceras calliphyllum. A few taxa, which went extinct everywhere else by the end of the Triassic, survived in the Tibetan Himalaya into early Early Jurassic times. They include the ammonites Choristoceras and Eopsiloceras, and the bivalves Newaagia, Terquemia, Persia, Ryderia guangdongensis, and Cultriopsis angusta. This suggests that the Tibetan Himalaya may have played a refugia role in the course of the end-Triassic mass extinction.

关键词： end-Triassic mass extinction paleobiogeography bivalves ammonites

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Interbasinal marker intervals——A case study from the Jurassic basins of Kachchh and Jaisalmer, western India

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Science China Earth Sciences 2009年第12期52卷 1924-1931页

作者： PANDEY Dhirendra Kumar fürsich franz theodor Department of Geology University of Rajasthan Jaipur 302004 India Institut für Geologie und Palontologie der Universitt Würzburg Pleicherwall 1 D-97070 Würzburg Germany GeoZentrum Nordbayern der Universitt Erlangen Loewenichstr. 28 D-91054 Erlangen Germany

The Kachchh Basin and the Jaisalmer Basin are two neighboring Mesozoic sedimentary basins at the western margin of the Indian craton. The Jurassic succession of the Kachchh Basin is more complete and more fossiliferous than that of the Jaisalmer Basin. Consequently, intrabasinal correlation of the sedimentary units has been possible in the Kachchh Basin, but not in the Jaisalmer Basin. However, some marker beds existing in the Kachchh Basin can be recognized also in the Jaisalmer Basin. Ammonite evidence shows that they are time-equivalent. The following four units form marker intervals in both basins: (1) the pebbly rudstone unit with Isastrea bernardiana and Leptosphinctes of the Kaladongar formation (Kachchh Basin) and the Isastrea bernardiana-bearing rudstone of the Jaisalmer formation (Jaisalmer Basin) both represent transgressive systems tract deposits dated as Late Bajocian; (2) bioturbated micrites with anomalodesmatan bivalves within the Goradongar Yellow flagstone Member (Kachchh Basin) and bioturbated units in the fort Member (Jaisalmer Basin) represent maximum flooding zone deposits of the Middle to Late Bathonian; (3) trough-crossbedded, sandy packto grainstones of the Raimalro Limestone Member (Kachchh Basin) and the basal limestone-sandstone unit of the Kuldhar section of the Jaisalmer formation (Jaisalmer Basin) correspond to Late Bathonain transgressive systems tract deposits; and (4) ferruginous ooid-bearing carbonates with hardgrounds of the Dhosa Oolite member (Kachchh Basin) and the middle part of the Jajiya Member (Jaisalmer Basin) are Oxfordian transgressive systems tract deposits. The fact that in both basins similar biofacies prevailed during certain time intervals demonstrates a common control of their depositional history. As the two basins represent different tectonic settings, the most likely controlling factors were the relative sea-level changes produced by eustatic processes, a common subsidence history of the northwestern margin of t

关键词： Jurassic interbasinal correlation marker beds sequence stratigraphy India

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Sequence architecture of a Jurassic ramp succession from Gebel Maghara(North Sinai,Egypt):Implications for eustasy

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Journal of Palaeogeography 2015年第3期4卷 305-330页

作者： Ahmed Awad Abdelhady franz theodor fürsich Geology Department Faculty of ScienceMinia University fG Pal?oumwelt Geozentrum Nordbayern der Universit?t Erlangen

The Jurassic succession at Gebet Maghara, North Sinai, Egypt, represents a mixed carbonate-siticictastic sequence. Combining information from both fossits and rocks attowed a ptausibte reconstruction of the depositionat environments and of the basin evotution. The Ju- rassic succession of Gebel Maghara was deposited on a ramp, and the architecture of the ramp facies was strongty controtted not onty by sea-revel changes but atso by extensionat tectonics in connection with rifting of the Tethys, North Gondwana. Seven tectonicalty modified thirdorder sequences （DS 1-DS 7） have been recognized. The first three sequences （DS 1-DS 3）, ranging from the Toarcian to the Bajocian, record sea invasion （intertidat to shattow subtida[lconditions） across an intracratonic area as a resutt of eustatic sea-fever changes during a quiescent rift stage. The remaining sequences （DS 4-DS 7） reflect open marine mid to outer ramp settings. Non-marine conditions around the Bajocian-Bathonian boundary, documented by catiche, represent the maximum regression of the sea. During an active extensionat stage, horsts, which formerty acted as barriers separating the Maghara sub-basin from the main ocean, subsided. Subsequent rejuvenation and reactivation of fautts shifted the homoctinat physiography of the ramp to a distatty steepened ramp during the earty Bathonian, creating a 200-m-thick dettaic wedge. SimiLar processes during the earty Kimmeridgian created a catcirudite-catcarenite succession of stope origin. The diversity and the epifaunat/infaunat percentage of the macrofauna disptay a cyctic pattern which coincides more or tess with the sequence stratigraphic architecture.

关键词： facies sequence stratigraphy ramp extensional basin Jurassic Gebel Maghara Egypt

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