ABSTRACT The definition of the Global Boundary Stratotype Section and Point (GSSP) of the Bathoni... more ABSTRACT The definition of the Global Boundary Stratotype Section and Point (GSSP) of the Bathonian/Callovian (Middle Jurassic) boundary is under debate in Europe. The sections that include the Bathonian/Callovian boundary are still limited in East Asia. In Japan, the Middle Jurassic Kaizara Formation, which is located within the Tetori Group, is exposed in Fukui Prefecture, central Japan. This formation contains abundant ammonite fossils. On the basis of ammonite fossils, the Kaizara Formation has been assigned to the late Bathonian to early Callovian age. Therefore, the Kaizara Formation is an important formation encompassing the Bathonian/Callovian boundary in East Asia. However, the fossil-bearing horizons have not been observed clearly in previous studies. In the present study, a detailed analysis of the molluscan fossil-bearing horizons of the Kaizara Formation was conducted utilizing three stratigraphic successions. On the basis of seven identified genera and nine species of ammonites, the presence of three successive assemblage zones first proposed by a previous study is confirmed: the Pseudoneuqueniceras yokoyamai, the Kepplerites japonicus, and the Oxycerites assemblage zones. Of these, the Pseudoneuqueniceras yokoyamai Assemblage Zone was assumed to correspond to the Orbis – Oppeli Zone (late Bathonian), and the Kepplerites assemblage Zone was assumed to be comparable to the early Callovian age. These results indicate that the Bathonian/Callovian boundary lies within the middle part of the Kaizara Formation.
The sections of Germig in the Nyalam area, southern Tibet, provide a continuous exposure of ammon... more The sections of Germig in the Nyalam area, southern Tibet, provide a continuous exposure of ammonoid-bearing, uppermost Triassic and basal Jurassic strata. Eighteen species (three of them new) are described and illustrated: Choristoceras marshi Hauer, C. aff. marshi, C. cf. nobile Mojsisovics, C. nyalamense sp. nov., Eopsiloceras germigense sp. nov., Pleuroacanthites aff. biformis (Sowerby), Rhacophyllites sp., Nevadaphyllites cf. psilomorphus (Neumayr), Neophyllites sp. indet., Neophyllites cf. biptychus (Lange), Psiloceras tibeticum sp. nov., P. calliphyllum (Neumayr), Euphyllites cf. struckmanni (Neumayr), Discamphiceras pleuronotum (Canavari), Alsatites spp., Kammerkarites frigga, and K. sp. The ammonoid fauna shows a strong affinity to that of the Northern Calcareous Alps, although diversity in the Calliphyllum Zone is markedly lower. The ammonoid succession across the Triassic ⁄ Jurassic boundary is subdivided into four zones: the Rhaetian Marshi, the basal Hettangian Tibeticum, the lower Hettangian Calliphyllum, and the middle Hettangian Pleuronotum zones. It is the only known succession across the Triassic ⁄ Jurassic boundary in the Tethyan Realm that is not condensed. The Marshi and Calliphyllum zones are correlated with the same zones in the Northern Calcareous Alps. The Tibeticum Zone, a new local zone, is transitional between the Marshi and the Calliphyllum zones in that it yields both choristoceratids and psiloceratids. Its base is taken to mark the base of the Jurassic System in the eastern Tethys.
There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleom... more There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleomagnetic, ESR and TL dating suggest that they date from the Late Pliocene to the Early Pleistocene. Analyses of stratigraphy, sedimentary Ž characteristic, and evolution of the fauna and flora indicate that, from the Pliocene to the early Quaternary about 5-1.1 Ma. BP , there was a relatively warm and humid environment, and a paleolake occurred around the Kunlun Pass. The elevation of the Kunlun Pass area was no more than 1500 m, and only one low topographic divide existed between the Qaidam Basin and the Kunlun Pass Basin. The geomorphic pattern in the Kunlun Pass area was influenced by the Kunlun-Yellow River Ž. Tectonic Movement 1.1-0.6 Ma BP. The Wangkun Glaciation 0.7-0.5 Ma is the maximum Quaternary glaciation in the Pass and in other areas of the Plateau. During the glaciation, the area of the glaciers was 3-5 times larger than that of the present glacier in the Pass area. There was no Xidatan Valley that time. The extreme geomorphic changes in the Kunlun Pass area reflect an abrupt uplift of the Tibet Plateau during the Early and Middle Pleistocene. This uplift of the Plateau has significance on both the Plateau itself and the surrounding area.
New data on Jurassic ammonites allow the establishment of a biostratigraphic framework of the Him... more New data on Jurassic ammonites allow the establishment of a biostratigraphic framework of the Himalayan Tibet. The recognition of Jurassic sea-level changes was obtained by combining shallowing-and deepening-upward cycles with palaeoecological information, and with information on intercontinental faunal dispersal. Major episodes of sea-level rise are now known to have taken place in the Middle Hettangian, Early Sinemurian, Late Pliensbachian to Early Toarcian, Early Bajocian, Late Bathonian to Early Callovian, Middle Oxfordian, Late Kimmeridgian, and late Early Tithonian. As a consequence, the results of earlier sequence stratigraphic analyses have to be modified. Jurassic, ammonites, sea-level changes, Himalayan Tibet
Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 1999
A good exposure of Triassic-Jurassic strata, named the Germ& section in the Lanongla area, south ... more A good exposure of Triassic-Jurassic strata, named the Germ& section in the Lanongla area, south Tibet has been investigated recently. Non-marine conditions of the Upper Triassic represented by the Zhamure formation existed in most of south Tibet, but they terminated in the area by the Germig formation which represents a marine transgression from the Late Norian-Rhaetian to the Early and Middle Hettangian. It is reported for the first time that Triassic-Jurassic passage beds with ammonite evidence have been found in Tethyan Himalaya. The earliest Jurassic faunas exhibit affinity with those of Nevada, implying a trans-Pacific dispersal in the early stage of biotic recovery after the end-Triassic mass extinction. (0 Acadkmie des sciences / Elsevier, Paris.) ammonites / Triassic-Jurassic boundary-passage beds / Tethyan Himalaya Resume-Un bon tieurement des couches de la limite Trias-Jurassique, la coupe de Germig, dans la region de Lanongla, Sud Tibet, a fait l'objet d'une etude kcente. Les milieux non marins du Trias supkrieur de la formation Zhamure sont presents dans la plus grande partie du Sud Tibet, mais, dans la region de Germig, ils sont termin& par une transgression marine, du Norien-RhCtien 3 1'Hettangien infkieur et moyen. C'est la premihe fois que des couches de passage Trias-Jurassique avec ammonites sont trouvkes dans 1'Himalaya tkthysien. Les prem2res faunes jurassiques montrent des &nit& avec celles du Nevada, ce qui implique une large dispersion trans-Pacifique au tout-debut de la reconquete biotique qui a suivi l'extinction en masse de la fin du Trias. (0 Acad&mie des sciences / Elsevier, Paris.) ammonites / couches de passage de la &mite Trias-Jurassique / Himalaya Why&en Version abreg6e (voir p. 131) * Correspondence and reprints.
A complete marine succession across the Triassic±Jurassic boundary is reported from southern Tibe... more A complete marine succession across the Triassic±Jurassic boundary is reported from southern Tibet, on the northern¯anks of the Himalayas. Both youngest Triassic and oldest Jurassic ammonites, together with palynological data, allow a combined facies and gamma ray study indicating no signi®cant change across the system boundary, unlike elsewhere in the world.
End-Triassic ammonoid and bivalve faunas of the Germig area, Tibetan Himalaya, lived in a tropica... more 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.
ABSTRACT Auszug The bivalve genusHudsonella, with the type speciesHudsonella sinensis (Chen) was ... more ABSTRACT Auszug The bivalve genusHudsonella, with the type speciesHudsonella sinensis (Chen) was described by Yin & Fürsich (1991: 107) from Middle Jurassic brackish water environments of the southern Qinghai province, China. As the generic name is pre-occupied byHudsonella Zacharias & Calman 1893, a rotiferan, the new nameHudsonina is herein proposed forHudsonella Yin & Fürsich. The type species of the genus consequently becomesHudsonina sinensis (Chen).
New Zealand Journal of Geology and Geophysics, 2004
Lupherella, previously thought endemic to the eastern Pacific, is now reported from eastern Guang... more Lupherella, previously thought endemic to the eastern Pacific, is now reported from eastern Guangdong, China. Associated ammonites prove a late Sinemurian to late Pliensbachian age for the bivalve assemblage consisting of Lupherella huidongensis, Lupherella cf. boechiformis, Otapiria cf. marshalli, Camptonectes (Hunanonectes) sp., and others. Appearance of Lupherella and Otapiria cf. marshalli in south China indicates trans-Pacific faunal dispersal during Early Jurassic times.
New Zealand Journal of Geology and Geophysics, 2005
Mesozoic volcanic sediments known as the Yeba Formation are widespread in the northeastern region... more Mesozoic volcanic sediments known as the Yeba Formation are widespread in the northeastern region of Lhasa. Recent fossil collections in the formation allow the establishment of a biostratigraphic framework for the volcanic sediments; bivalves are assigned to 21 genera and 22 species including a new genus and 5 new species: Lhasanella lhasaensis (gen. et sp. nov.), Trigonodus xiabolangensis (sp. nov.), Isocyprina lhasaensis (sp. nov.), Gervillaria tibetica (sp. nov.), and Jurassicorbula fuersichi (sp. nov.). Three benthic assemblages have been recognised: the Trigonodus-Isocyprina assemblage (Rhaetian-Hettangian), the Lhasanella-Propeamussium assemblage (Toarcian-Bajocian), and the Jurassicorbula-Neomiodon assemblage (Middle Jurassic). The Yeba Formation ranges in age from latest Triassic to Middle Jurassic. Volcanism in the Lhasa block occurred frequently during this period, corresponding to the fragmentation episode in eastern Gondwanaland and to the northwards drift of the Lhasa block. A strong faunal affinity between the Lhasa block and southern Qinghai, Japan, and Vietnam suggests that the Lhasa block had been located within the northern marginal region of the East Tethys since Toarcian times. The existence of a deep ocean which might serve as a barrier to fauna dispersal between the Lhasa and Qingtang blocks remains questionable.
Middle Jurassic ammonites collected in situ from the Lanongla sections, Lanongla, South Tibet all... more Middle Jurassic ammonites collected in situ from the Lanongla sections, Lanongla, South Tibet allow the precise dating of the ferruginous Oolite beds and the underlying limestone beds in this area. A large hiatus of 8 million-year duration in South Tibet is well documented by the ammonite succession. Revision of sea-level changes curve in Tibet during the Middle Jurassic is proposed; the high sea-level stands below and above the disconformity are dated as Humphriesianum Zone (late Early Bajocian) and Orbis Zone (early Late Bathonian), respectively.
The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensi... more The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensive sequence of ammonoid fauna. New collections in situ through the Lanongla, Pure, Gucuo and Jiapeila sections have facilitated a major revision of the ammonoid assemblages. Probably due to depositional facies segregation, the Belemnopsis galoi-bearing beds can be regarded as the oldest Tithonian sediments in which the basal Tithonian ammonoid Kossmatia is not present. The Lower Tithonian includes the Virgatosphinctes-Aulacosphinctoides and Uhligites-Aulacosphinctes assemblages; the Upper Tithonian includes the Haplophylloceras pingue, Blanfordiceras wallichi and Haplophylloceras strigile-Corongoceras-Himalayites assemblages. The Spiticeras assemblage is suggested to be from the Lowermost Berriasian. The new ammonoid assemblages at well-defined levels in Himalayan Tibet provide some crucial links for correlation with other regions of the SW Pacific domain where these ammonoid genera have been widely distributed.
The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant... more The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant bivalve fauna which has been found in association with choristoceratid and psiloceratid ammonoids and spans the Triassic/Jurassic boundary. The bivalve fauna consists of 25 species, including four new species: Newaagia lanonglaensis, Persia hallami, Liostrea tibetica, and Ctenostreon newelli. The fauna comprises three biostratigraphically controlled bivalve assemblages: 1) an upper Rhaetian Palaeocardita-Krumbeckiella Assemblage including seven species; 2) a high diversity transitional Rhaetian-Hettangian Persia-Plagiostoma Assemblage with many as 19 species; and 3) a low diversity lower Hettangian Liostrea-Chlamys Assemblage containing three species. The transitional Rhaetian-Hettangian Assemblage is dominated by cementing species and exhibits a high degree of endemism. A large proportion of lower latitude and cementing taxa from the lower two levels may indicate that they inhabited shallow subtidal tropic or subtropic paleoenvironments.
ABSTRACT The definition of the Global Boundary Stratotype Section and Point (GSSP) of the Bathoni... more ABSTRACT The definition of the Global Boundary Stratotype Section and Point (GSSP) of the Bathonian/Callovian (Middle Jurassic) boundary is under debate in Europe. The sections that include the Bathonian/Callovian boundary are still limited in East Asia. In Japan, the Middle Jurassic Kaizara Formation, which is located within the Tetori Group, is exposed in Fukui Prefecture, central Japan. This formation contains abundant ammonite fossils. On the basis of ammonite fossils, the Kaizara Formation has been assigned to the late Bathonian to early Callovian age. Therefore, the Kaizara Formation is an important formation encompassing the Bathonian/Callovian boundary in East Asia. However, the fossil-bearing horizons have not been observed clearly in previous studies. In the present study, a detailed analysis of the molluscan fossil-bearing horizons of the Kaizara Formation was conducted utilizing three stratigraphic successions. On the basis of seven identified genera and nine species of ammonites, the presence of three successive assemblage zones first proposed by a previous study is confirmed: the Pseudoneuqueniceras yokoyamai, the Kepplerites japonicus, and the Oxycerites assemblage zones. Of these, the Pseudoneuqueniceras yokoyamai Assemblage Zone was assumed to correspond to the Orbis – Oppeli Zone (late Bathonian), and the Kepplerites assemblage Zone was assumed to be comparable to the early Callovian age. These results indicate that the Bathonian/Callovian boundary lies within the middle part of the Kaizara Formation.
The sections of Germig in the Nyalam area, southern Tibet, provide a continuous exposure of ammon... more The sections of Germig in the Nyalam area, southern Tibet, provide a continuous exposure of ammonoid-bearing, uppermost Triassic and basal Jurassic strata. Eighteen species (three of them new) are described and illustrated: Choristoceras marshi Hauer, C. aff. marshi, C. cf. nobile Mojsisovics, C. nyalamense sp. nov., Eopsiloceras germigense sp. nov., Pleuroacanthites aff. biformis (Sowerby), Rhacophyllites sp., Nevadaphyllites cf. psilomorphus (Neumayr), Neophyllites sp. indet., Neophyllites cf. biptychus (Lange), Psiloceras tibeticum sp. nov., P. calliphyllum (Neumayr), Euphyllites cf. struckmanni (Neumayr), Discamphiceras pleuronotum (Canavari), Alsatites spp., Kammerkarites frigga, and K. sp. The ammonoid fauna shows a strong affinity to that of the Northern Calcareous Alps, although diversity in the Calliphyllum Zone is markedly lower. The ammonoid succession across the Triassic ⁄ Jurassic boundary is subdivided into four zones: the Rhaetian Marshi, the basal Hettangian Tibeticum, the lower Hettangian Calliphyllum, and the middle Hettangian Pleuronotum zones. It is the only known succession across the Triassic ⁄ Jurassic boundary in the Tethyan Realm that is not condensed. The Marshi and Calliphyllum zones are correlated with the same zones in the Northern Calcareous Alps. The Tibeticum Zone, a new local zone, is transitional between the Marshi and the Calliphyllum zones in that it yields both choristoceratids and psiloceratids. Its base is taken to mark the base of the Jurassic System in the eastern Tethys.
There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleom... more There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleomagnetic, ESR and TL dating suggest that they date from the Late Pliocene to the Early Pleistocene. Analyses of stratigraphy, sedimentary Ž characteristic, and evolution of the fauna and flora indicate that, from the Pliocene to the early Quaternary about 5-1.1 Ma. BP , there was a relatively warm and humid environment, and a paleolake occurred around the Kunlun Pass. The elevation of the Kunlun Pass area was no more than 1500 m, and only one low topographic divide existed between the Qaidam Basin and the Kunlun Pass Basin. The geomorphic pattern in the Kunlun Pass area was influenced by the Kunlun-Yellow River Ž. Tectonic Movement 1.1-0.6 Ma BP. The Wangkun Glaciation 0.7-0.5 Ma is the maximum Quaternary glaciation in the Pass and in other areas of the Plateau. During the glaciation, the area of the glaciers was 3-5 times larger than that of the present glacier in the Pass area. There was no Xidatan Valley that time. The extreme geomorphic changes in the Kunlun Pass area reflect an abrupt uplift of the Tibet Plateau during the Early and Middle Pleistocene. This uplift of the Plateau has significance on both the Plateau itself and the surrounding area.
New data on Jurassic ammonites allow the establishment of a biostratigraphic framework of the Him... more New data on Jurassic ammonites allow the establishment of a biostratigraphic framework of the Himalayan Tibet. The recognition of Jurassic sea-level changes was obtained by combining shallowing-and deepening-upward cycles with palaeoecological information, and with information on intercontinental faunal dispersal. Major episodes of sea-level rise are now known to have taken place in the Middle Hettangian, Early Sinemurian, Late Pliensbachian to Early Toarcian, Early Bajocian, Late Bathonian to Early Callovian, Middle Oxfordian, Late Kimmeridgian, and late Early Tithonian. As a consequence, the results of earlier sequence stratigraphic analyses have to be modified. Jurassic, ammonites, sea-level changes, Himalayan Tibet
Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 1999
A good exposure of Triassic-Jurassic strata, named the Germ& section in the Lanongla area, south ... more A good exposure of Triassic-Jurassic strata, named the Germ& section in the Lanongla area, south Tibet has been investigated recently. Non-marine conditions of the Upper Triassic represented by the Zhamure formation existed in most of south Tibet, but they terminated in the area by the Germig formation which represents a marine transgression from the Late Norian-Rhaetian to the Early and Middle Hettangian. It is reported for the first time that Triassic-Jurassic passage beds with ammonite evidence have been found in Tethyan Himalaya. The earliest Jurassic faunas exhibit affinity with those of Nevada, implying a trans-Pacific dispersal in the early stage of biotic recovery after the end-Triassic mass extinction. (0 Acadkmie des sciences / Elsevier, Paris.) ammonites / Triassic-Jurassic boundary-passage beds / Tethyan Himalaya Resume-Un bon tieurement des couches de la limite Trias-Jurassique, la coupe de Germig, dans la region de Lanongla, Sud Tibet, a fait l'objet d'une etude kcente. Les milieux non marins du Trias supkrieur de la formation Zhamure sont presents dans la plus grande partie du Sud Tibet, mais, dans la region de Germig, ils sont termin& par une transgression marine, du Norien-RhCtien 3 1'Hettangien infkieur et moyen. C'est la premihe fois que des couches de passage Trias-Jurassique avec ammonites sont trouvkes dans 1'Himalaya tkthysien. Les prem2res faunes jurassiques montrent des &nit& avec celles du Nevada, ce qui implique une large dispersion trans-Pacifique au tout-debut de la reconquete biotique qui a suivi l'extinction en masse de la fin du Trias. (0 Acad&mie des sciences / Elsevier, Paris.) ammonites / couches de passage de la &mite Trias-Jurassique / Himalaya Why&en Version abreg6e (voir p. 131) * Correspondence and reprints.
A complete marine succession across the Triassic±Jurassic boundary is reported from southern Tibe... more A complete marine succession across the Triassic±Jurassic boundary is reported from southern Tibet, on the northern¯anks of the Himalayas. Both youngest Triassic and oldest Jurassic ammonites, together with palynological data, allow a combined facies and gamma ray study indicating no signi®cant change across the system boundary, unlike elsewhere in the world.
End-Triassic ammonoid and bivalve faunas of the Germig area, Tibetan Himalaya, lived in a tropica... more 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.
ABSTRACT Auszug The bivalve genusHudsonella, with the type speciesHudsonella sinensis (Chen) was ... more ABSTRACT Auszug The bivalve genusHudsonella, with the type speciesHudsonella sinensis (Chen) was described by Yin & Fürsich (1991: 107) from Middle Jurassic brackish water environments of the southern Qinghai province, China. As the generic name is pre-occupied byHudsonella Zacharias & Calman 1893, a rotiferan, the new nameHudsonina is herein proposed forHudsonella Yin & Fürsich. The type species of the genus consequently becomesHudsonina sinensis (Chen).
New Zealand Journal of Geology and Geophysics, 2004
Lupherella, previously thought endemic to the eastern Pacific, is now reported from eastern Guang... more Lupherella, previously thought endemic to the eastern Pacific, is now reported from eastern Guangdong, China. Associated ammonites prove a late Sinemurian to late Pliensbachian age for the bivalve assemblage consisting of Lupherella huidongensis, Lupherella cf. boechiformis, Otapiria cf. marshalli, Camptonectes (Hunanonectes) sp., and others. Appearance of Lupherella and Otapiria cf. marshalli in south China indicates trans-Pacific faunal dispersal during Early Jurassic times.
New Zealand Journal of Geology and Geophysics, 2005
Mesozoic volcanic sediments known as the Yeba Formation are widespread in the northeastern region... more Mesozoic volcanic sediments known as the Yeba Formation are widespread in the northeastern region of Lhasa. Recent fossil collections in the formation allow the establishment of a biostratigraphic framework for the volcanic sediments; bivalves are assigned to 21 genera and 22 species including a new genus and 5 new species: Lhasanella lhasaensis (gen. et sp. nov.), Trigonodus xiabolangensis (sp. nov.), Isocyprina lhasaensis (sp. nov.), Gervillaria tibetica (sp. nov.), and Jurassicorbula fuersichi (sp. nov.). Three benthic assemblages have been recognised: the Trigonodus-Isocyprina assemblage (Rhaetian-Hettangian), the Lhasanella-Propeamussium assemblage (Toarcian-Bajocian), and the Jurassicorbula-Neomiodon assemblage (Middle Jurassic). The Yeba Formation ranges in age from latest Triassic to Middle Jurassic. Volcanism in the Lhasa block occurred frequently during this period, corresponding to the fragmentation episode in eastern Gondwanaland and to the northwards drift of the Lhasa block. A strong faunal affinity between the Lhasa block and southern Qinghai, Japan, and Vietnam suggests that the Lhasa block had been located within the northern marginal region of the East Tethys since Toarcian times. The existence of a deep ocean which might serve as a barrier to fauna dispersal between the Lhasa and Qingtang blocks remains questionable.
Middle Jurassic ammonites collected in situ from the Lanongla sections, Lanongla, South Tibet all... more Middle Jurassic ammonites collected in situ from the Lanongla sections, Lanongla, South Tibet allow the precise dating of the ferruginous Oolite beds and the underlying limestone beds in this area. A large hiatus of 8 million-year duration in South Tibet is well documented by the ammonite succession. Revision of sea-level changes curve in Tibet during the Middle Jurassic is proposed; the high sea-level stands below and above the disconformity are dated as Humphriesianum Zone (late Early Bajocian) and Orbis Zone (early Late Bathonian), respectively.
The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensi... more The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensive sequence of ammonoid fauna. New collections in situ through the Lanongla, Pure, Gucuo and Jiapeila sections have facilitated a major revision of the ammonoid assemblages. Probably due to depositional facies segregation, the Belemnopsis galoi-bearing beds can be regarded as the oldest Tithonian sediments in which the basal Tithonian ammonoid Kossmatia is not present. The Lower Tithonian includes the Virgatosphinctes-Aulacosphinctoides and Uhligites-Aulacosphinctes assemblages; the Upper Tithonian includes the Haplophylloceras pingue, Blanfordiceras wallichi and Haplophylloceras strigile-Corongoceras-Himalayites assemblages. The Spiticeras assemblage is suggested to be from the Lowermost Berriasian. The new ammonoid assemblages at well-defined levels in Himalayan Tibet provide some crucial links for correlation with other regions of the SW Pacific domain where these ammonoid genera have been widely distributed.
The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant... more The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant bivalve fauna which has been found in association with choristoceratid and psiloceratid ammonoids and spans the Triassic/Jurassic boundary. The bivalve fauna consists of 25 species, including four new species: Newaagia lanonglaensis, Persia hallami, Liostrea tibetica, and Ctenostreon newelli. The fauna comprises three biostratigraphically controlled bivalve assemblages: 1) an upper Rhaetian Palaeocardita-Krumbeckiella Assemblage including seven species; 2) a high diversity transitional Rhaetian-Hettangian Persia-Plagiostoma Assemblage with many as 19 species; and 3) a low diversity lower Hettangian Liostrea-Chlamys Assemblage containing three species. The transitional Rhaetian-Hettangian Assemblage is dominated by cementing species and exhibits a high degree of endemism. A large proportion of lower latitude and cementing taxa from the lower two levels may indicate that they inhabited shallow subtidal tropic or subtropic paleoenvironments.
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