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Jiajie Chen - One of the best experts on this subject based on the ideXlab platform.

  • proto tethys magmatic evolution along northern gondwana insights from late silurian Middle Devonian a type magmatism east kunlun orogen northern tibetan plateau china
    Lithos, 2020
    Co-Authors: Xu Zhao, Jiajie Chen, Junhao Wei, David Selby, Daohan Zhang, Hongzhi Zhou, Yan Liu
    Abstract:

    Abstract The East Kunlun Orogen records the geological evolutions of the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean and Late Paleozoic–Mesozoic Paleo-Tethys Ocean along northern Gondwana. However, the late-stage evolution of the Proto-Tethyan Ocean and the configuration of peri-Gondwana microcontinents during the Silurian – Devonian is under debate. Here we report new geochronological and geochemical data of A-type granites from the western Wulonggou and the eastern Gouli areas in the East Kunlun Orogen to deepen our understanding of these problems. Zircon LA-ICP-MS U Pb data reveal that the Danshuigou monzogranite and Shenshuitan syenogranite from the western Wulonggou area were emplaced simultaneously at 418 ± 3 Ma, while the Niantang syenogranite from the eastern Gouli area was emplaced at 403 ± 2 Ma. All these rocks display high-K calcic-alkalic to shoshonitic and metaluminous to slight peraluminous signatures, with relatively low CaO, Al2O3, MgO and Sr, and high FeOt/MgO, Ga/Al, Zr, and Nb, indicating their A-type affinity. Their moderate whole-rock eNd(t) (−5.3 to −0.6) and zircon eHf(t) (−6.3–6.4) are different from those of depleted mantle and old basement rocks, but similar to those of the Ordovician–Silurian granitoids in the East Kunlun Orogen. These chemical signatures, together with the anhydrous, low-pressure and high-temperature characteristics of the magmas, indicate that partial melting of the Ordovician–Silurian granitoids generated these A-type granites. Regionally, these A-type granites and previously reported A-type granites in the East Kunlun Orogen compose a Late Silurian – Middle Devonian A-type granite belt. This belt, together with the regionally coeval molasse formation and mafic-ultramafic rocks, indicate a post-collisional extensional regime for the East Kunlun Orogen during the Late Silurian – Middle Devonian. Given that extensive contemporaneous post-collision-related magmatic rocks have also been revealed in the neighboring West Kunlun, Altyn, Qilian and Qinling blocks/terranes, we contend that the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean that separated these blocks/terranes from Gondwana had closed by the Late Silurian – Middle Devonian, which]resulted in the re-welding of the above blocks/terranes to northern Gondwana or Gondwana-derived microcontinents.

Yan Liu - One of the best experts on this subject based on the ideXlab platform.

  • proto tethys magmatic evolution along northern gondwana insights from late silurian Middle Devonian a type magmatism east kunlun orogen northern tibetan plateau china
    Lithos, 2020
    Co-Authors: Xu Zhao, Jiajie Chen, Junhao Wei, David Selby, Daohan Zhang, Hongzhi Zhou, Yan Liu
    Abstract:

    Abstract The East Kunlun Orogen records the geological evolutions of the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean and Late Paleozoic–Mesozoic Paleo-Tethys Ocean along northern Gondwana. However, the late-stage evolution of the Proto-Tethyan Ocean and the configuration of peri-Gondwana microcontinents during the Silurian – Devonian is under debate. Here we report new geochronological and geochemical data of A-type granites from the western Wulonggou and the eastern Gouli areas in the East Kunlun Orogen to deepen our understanding of these problems. Zircon LA-ICP-MS U Pb data reveal that the Danshuigou monzogranite and Shenshuitan syenogranite from the western Wulonggou area were emplaced simultaneously at 418 ± 3 Ma, while the Niantang syenogranite from the eastern Gouli area was emplaced at 403 ± 2 Ma. All these rocks display high-K calcic-alkalic to shoshonitic and metaluminous to slight peraluminous signatures, with relatively low CaO, Al2O3, MgO and Sr, and high FeOt/MgO, Ga/Al, Zr, and Nb, indicating their A-type affinity. Their moderate whole-rock eNd(t) (−5.3 to −0.6) and zircon eHf(t) (−6.3–6.4) are different from those of depleted mantle and old basement rocks, but similar to those of the Ordovician–Silurian granitoids in the East Kunlun Orogen. These chemical signatures, together with the anhydrous, low-pressure and high-temperature characteristics of the magmas, indicate that partial melting of the Ordovician–Silurian granitoids generated these A-type granites. Regionally, these A-type granites and previously reported A-type granites in the East Kunlun Orogen compose a Late Silurian – Middle Devonian A-type granite belt. This belt, together with the regionally coeval molasse formation and mafic-ultramafic rocks, indicate a post-collisional extensional regime for the East Kunlun Orogen during the Late Silurian – Middle Devonian. Given that extensive contemporaneous post-collision-related magmatic rocks have also been revealed in the neighboring West Kunlun, Altyn, Qilian and Qinling blocks/terranes, we contend that the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean that separated these blocks/terranes from Gondwana had closed by the Late Silurian – Middle Devonian, which]resulted in the re-welding of the above blocks/terranes to northern Gondwana or Gondwana-derived microcontinents.

Yi Wang - One of the best experts on this subject based on the ideXlab platform.

  • the earliest cormose rhizomorph of putative lycopsid affinity from the Middle Devonian of west junggar xinjiang china
    Review of Palaeobotany and Palynology, 2016
    Co-Authors: Yi Wang
    Abstract:

    Abstract Impression fossils of a cormose rhizomorph are described from the Givetian (late Middle Devonian) Hujiersite Formation, Hoxtolgay, West Junggar, Xinjiang, Northwest China. The rhizomorph is bulbous, with densely arranged, oval rootlet bases enclosing orbicular vascular bundle scars, exhibiting considerable resemblance to that of the Late Devonian–Carboniferous rhizomorphic lycopsid of Isoetales sensu stricto . The present specimens may represent the earliest cormose lycopsid rhizomorph. Their implications for the origin and early evolution of rhizomorphic lycopsids are discussed.

  • A NEW HOMOSPOROUS, ARBORESCENT LYCOPSID FROM THE Middle Devonian OF XINJIANG, NORTHWEST CHINA
    Palaeontology, 2012
    Co-Authors: Yi Wang, Qi Wang
    Abstract:

    A new arborescent lycopsid, Hoxtolgaya robusta gen. et sp. nov., is described from the Middle Devonian of Xinjiang, Northwest China. It has stems up to 90 mm wide with fusiform leaf bases and long linear microphylls. Sporophylls are not aggregated into strobili and are iso- morphic, with sporangia homosporous and bearing Acinosporites-type microspores. A syndrome of characters in Hoxtolgaya, including the arborescence and the homo- spory, implies that the arborescent habit is not necessarily correlated with the heterospory in the early evolu- tion of arborescent lycopsids. Homosporous, arborescent lycopsids probably represent one of the transient forms between the Devonian herbaceous protolepidodendrids and the Devonian-Carboniferous heterosporous arborescent lycopsids.

  • a neotype for colpodexylon gracilentum dou lycopsida from the Middle Devonian of north xinjiang china
    Journal of Systematics and Evolution, 2011
    Co-Authors: X U Honghe, Yi Wang
    Abstract:

    According to newly collected and well preserved specimens, herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang, NW China are reduced to C. gracilentum, for which a neotype is designated and emended diagnosis is given. Colpodexylon gracilentum has leaves with three nearly equal segments, an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.

  • A New Species of Leclercqia Banks, Bonamo et Grierson (Lycopsida) from the Middle Devonian of North Xinjiang, China, with a Possible Climbing Habit
    International Journal of Plant Sciences, 2011
    Co-Authors: Christopher Mark Berry, Yi Wang, John E. A. Marshall
    Abstract:

    A new herbaceous lycopsid species, Leclercqia uncinata Xu, Berry, Wang et Marshall, is established on the basis of compression fossils from the Middle Devonian of Xinjiang, NW China. The new species has slender axes and three-dimensional, seven-tipped leaves with a distally hooked central segment conforming to the original diagnosis of the genus, and it is relatively smaller than the type species, L. complexa from New York State. The sporangium contains the spore, which can be assigned to morphotaxon Acinoporites lindlariensis. In our preparation of compressions, iridopteridalean fertile appendages are found trapped between the distally hooked leaves of L. uncinata. A possible climbing habit of the new plant is discussed.

  • two species of haskinsia grierson banks lycopsida from the Middle Devonian of xinjiang china and consideration of their palaeogeographical significance
    Botanical Journal of the Linnean Society, 2008
    Co-Authors: Yi Wang, Christopher Mark Berry, Chongyang Cai
    Abstract:

    Two species of the Devonian herbaceous lycopsid Haskinsia Grierson & Banks, H. hastata Berry & Edwards and H. sagittata Edwards & Benedetto, are reported from the Hujiersite Formation (Givetian–Middle Devonian), Xinjiang, north-west China. Both species were first described from Venezuela. Haskinsia hastata from Xinjiang has hastate leaves with toothed margins, and a pair of basal narrow lateral segments which curve distally. It is assigned to a new subspecies because of the toothed margins which cannot be demonstrated in Venezuelan material. The scar of the sporangium stalk is observed for the first time in specimens of H. sagittata, on the leaves of which a possible ligule structure is also shown. On the basis of our observations on both Xinjiang and Venezuelan specimens, the diagnosis of Haskinsia is enlarged to accommodate plants whose lamina has entire or toothed margins. The palaeophytogeography of the genus, otherwise known from South and North America, is discussed.

Christian Klug - One of the best experts on this subject based on the ideXlab platform.

  • A large Middle Devonian eubrachythoracid ‘placoderm’ (Arthrodira) jaw from northern Gondwana
    Swiss Journal of Palaeontology, 2021
    Co-Authors: Melina Jobbins, Martin Rucklin, Thodoris Argyriou, Christian Klug
    Abstract:

    For the understanding of the evolution of jawed vertebrates and jaws and teeth, ‘placoderms’ are crucial as they exhibit an impressive morphological disparity associated with the early stages of this process. The Devonian of Morocco is famous for its rich occurrences of arthrodire ‘placoderms’. While Late Devonian strata are rich in arthrodire remains, they are less common in older strata. Here, we describe a large tooth-bearing jaw element of Leptodontichthys ziregensis gen. et sp. nov., an eubrachythoracid arthrodire from the Middle Devonian of Morocco. This species is based on a large posterior superognathal with a strong dentition. The jawbone displays features considered synapomorphies of Late Devonian eubrachythoracid arthrodires, with one posterior and one lateral row of conical teeth oriented postero-lingually. μCT-images reveal internal structures including pulp cavities and dentinous tissues. The posterior orientation of the teeth and the traces of a putative occlusal contact on the lingual side of the bone imply that these teeth were hardly used for feeding. Similar to Compagopiscis and Plourdosteus , functional teeth were possibly present during an earlier developmental stage and have been worn entirely. The morphological features of the jaw element suggest a close relationship with plourdosteids. Its size implies that the animal was rather large.

  • Spatial distribution of oncocerid cephalopods on a Middle Devonian bedding plane suggests semelparous life cycle.
    Scientific reports, 2020
    Co-Authors: Alexander Pohle, Dirk Fuchs, Dieter Korn, Christian Klug
    Abstract:

    Reproductive strategies of extinct organisms can only be recognised indirectly and hence, they are exceedingly rarely reported and tend to be speculative. Here, we present a mass-occurrence with common preservation of pairs of late Givetian (Middle Devonian) oncocerid cephalopods from Hamar Laghdad in the Tafilalt (eastern Anti-Atlas, Morocco). We analysed their spatial occurrences with spatial point pattern analysis techniques and Monte Carlo simulations; our results shows that the pairwise clustering is significant, while ammonoids on the same bedding plane reveal a more random distribution. It is possible that processes such as catastrophic mass mortality or post-mortem transport could have produced the pattern. However, we suggest that it is more likely that the oncocerids were semelparous and died shortly after mating. These findings shed new light on the variation and evolution of reproductive strategies in fossil cephalopods and emphasise that they cannot be based on comparisons with extant taxa without question.

  • morphological pathways in the evolution of early and Middle Devonian ammonoids
    Paleobiology, 2003
    Co-Authors: Dieter Korn, Christian Klug
    Abstract:

    The principal conch parameters—whorl expansion rate, whorl overlap rate, umbilical width, and whorl thickness—of Early and Middle Devonian ammonoids have been extensively investigated. Stratophenetic analyses show long-term trends in the transformations of these characters over long periods of time, but sudden and rapid reversals can also be observed. On the basis of these four quantifiable conch parameters and supplementary qualitative characters, ten ammonoid morphs were distinguished. Reconstruction of the evolutionary history of these morphs reflects the existence of two major phylogenetic lineages, both already visible in Early Devonian faunas. The agoniatitid lineage is characterized by slow character development and leads to the Frasnian gephuroceratids; the anarcestid lineage displays rapid morphological evolution that leads to the late Givetian pharciceratids as well as the Middle and Late Devonian tornoceratids. Morphological evolution is interpreted as partly limited by geometrical and physical constraints.

Xu Zhao - One of the best experts on this subject based on the ideXlab platform.

  • proto tethys magmatic evolution along northern gondwana insights from late silurian Middle Devonian a type magmatism east kunlun orogen northern tibetan plateau china
    Lithos, 2020
    Co-Authors: Xu Zhao, Jiajie Chen, Junhao Wei, David Selby, Daohan Zhang, Hongzhi Zhou, Yan Liu
    Abstract:

    Abstract The East Kunlun Orogen records the geological evolutions of the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean and Late Paleozoic–Mesozoic Paleo-Tethys Ocean along northern Gondwana. However, the late-stage evolution of the Proto-Tethyan Ocean and the configuration of peri-Gondwana microcontinents during the Silurian – Devonian is under debate. Here we report new geochronological and geochemical data of A-type granites from the western Wulonggou and the eastern Gouli areas in the East Kunlun Orogen to deepen our understanding of these problems. Zircon LA-ICP-MS U Pb data reveal that the Danshuigou monzogranite and Shenshuitan syenogranite from the western Wulonggou area were emplaced simultaneously at 418 ± 3 Ma, while the Niantang syenogranite from the eastern Gouli area was emplaced at 403 ± 2 Ma. All these rocks display high-K calcic-alkalic to shoshonitic and metaluminous to slight peraluminous signatures, with relatively low CaO, Al2O3, MgO and Sr, and high FeOt/MgO, Ga/Al, Zr, and Nb, indicating their A-type affinity. Their moderate whole-rock eNd(t) (−5.3 to −0.6) and zircon eHf(t) (−6.3–6.4) are different from those of depleted mantle and old basement rocks, but similar to those of the Ordovician–Silurian granitoids in the East Kunlun Orogen. These chemical signatures, together with the anhydrous, low-pressure and high-temperature characteristics of the magmas, indicate that partial melting of the Ordovician–Silurian granitoids generated these A-type granites. Regionally, these A-type granites and previously reported A-type granites in the East Kunlun Orogen compose a Late Silurian – Middle Devonian A-type granite belt. This belt, together with the regionally coeval molasse formation and mafic-ultramafic rocks, indicate a post-collisional extensional regime for the East Kunlun Orogen during the Late Silurian – Middle Devonian. Given that extensive contemporaneous post-collision-related magmatic rocks have also been revealed in the neighboring West Kunlun, Altyn, Qilian and Qinling blocks/terranes, we contend that the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean that separated these blocks/terranes from Gondwana had closed by the Late Silurian – Middle Devonian, which]resulted in the re-welding of the above blocks/terranes to northern Gondwana or Gondwana-derived microcontinents.

  • Proto-Tethys magmatic evolution along northern Gondwana : insights from Late Silurian–Middle Devonian A-type magmatism, East Kunlun Orogen, Northern Tibetan Plateau, China.
    'Elsevier BV', 2020
    Co-Authors: Chen Jiajie, Fu Lebing, Wei Junhao, Selby David, Zhang Daohan, Zhou Hongzhi, Xu Zhao, Liu Yan
    Abstract:

    The East Kunlun Orogen records the geological evolutions of the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean and Late Paleozoic–Mesozoic Paleo-Tethys Ocean along northern Gondwana. However, the late-stage evolution of the Proto-Tethyan Ocean and the configuration of peri-Gondwana microcontinents during the Silurian – Devonian is under debate. Here we report new geochronological and geochemical data of A-type granites from the western Wulonggou and the eastern Gouli areas in the East Kunlun Orogen to deepen our understanding of these problems. Zircon LA-ICP-MS UPb data reveal that the Danshuigou monzogranite and Shenshuitan syenogranite from the western Wulonggou area were emplaced simultaneously at 418 ± 3 Ma, while the Niantang syenogranite from the eastern Gouli area was emplaced at 403 ± 2 Ma. All these rocks display high-K calcic-alkalic to shoshonitic and metaluminous to slight peraluminous signatures, with relatively low CaO, Al2O3, MgO and Sr, and high FeOt/MgO, Ga/Al, Zr, and Nb, indicating their A-type affinity. Their moderate whole-rock εNd(t) (−5.3 to −0.6) and zircon εHf(t) (−6.3–6.4) are different from those of depleted mantle and old basement rocks, but similar to those of the Ordovician–Silurian granitoids in the East Kunlun Orogen. These chemical signatures, together with the anhydrous, low-pressure and high-temperature characteristics of the magmas, indicate that partial melting of the Ordovician–Silurian granitoids generated these A-type granites. Regionally, these A-type granites and previously reported A-type granites in the East Kunlun Orogen compose a Late Silurian – Middle Devonian A-type granite belt. This belt, together with the regionally coeval molasse formation and mafic-ultramafic rocks, indicate a post-collisional extensional regime for the East Kunlun Orogen during the Late Silurian – Middle Devonian. Given that extensive contemporaneous post-collision-related magmatic rocks have also been revealed in the neighboring West Kunlun, Altyn, Qilian and Qinling blocks/terranes, we contend that the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean that separated these blocks/terranes from Gondwana had closed by the Late Silurian – Middle Devonian, which]resulted in the re-welding of the above blocks/terranes to northern Gondwana or Gondwana-derived microcontinents