New theropod tracks from the Callovian of Tunisia: implications for Middle Jurassic theropod diversity along the northern margin of Gondwana

Silurian A-type metaquartz-syenite to -granite in the Eastern Anatolia: Implications for Late Ordovician-Silurian rifting at the northern margin of Gondwana

The Neoproterozoic-Early Cambrian evolution of peri-Gondwanan terranes (e.g. Avalonia, Carolinia, Cadomia) along the northern (Amazonia, West Africa) margin of Gondwana provides insights into the amalgamation of West Gondwana. The main phase of tectonothermal activity occurred between ca. 640–540 Ma and produced voluminous arc-related igneous and sedimentary successions related to subduction beneath the northern Gondwana margin. Subduction was not terminated by continental collision so that these terranes continued to face an open ocean into the Cambrian. Prior to the main phase of tectonothermal activity, Sm-Nd isotopic studies suggest that the basement of Avalonia, Carolinia and part of Cadomia was juvenile lithosphere generated between 0.8 and 1.1 Ga within the peri-Rodinian (Mirovoi) ocean. Vestiges of primitive 760–670 Ma arcs developed upon this lithosphere are preserved. Juvenile lithosphere generated between 0.8 and 1.1 Ga also underlies arcs formed in the Brazilide Ocean between the converging Congo/Sao Francisco and West Africa/Amazonia cratons (e.g. the Tocantins province of Brazil). Together, these juvenile arc assemblages with similar isotopic characteristics may reflect subduction in the Mirovoi and Brazilide oceans as a compensation for the ongoing breakup of Rodinia and the generation of the Paleopacific. Unlike the peri-Gondwanan terranes, however, arc magmatism in the Brazilide Ocean was terminated by continent-continent collisions and the resulting orogens became located within the interior of an amalgamated West Gondwana. Accretion of juvenile peri-Gondwanan terranes to the northern Gondwanan margin occurred in a piecemeal fashion between 650 and 600 Ma, after which subduction stepped outboard to produce the relatively mature and voluminous main arc phase along the periphery of West Gondwana. This accretionary event may be a far-field response to the breakup of Rodinia. The geodynamic relationship between the closure of the Brazilide Ocean, the collision between the Congo/Sao Francisco and Amazonia/West Africa cratons, and the tectonic evolution of the peri-Gondwanan terranes may be broadly analogous to the Mesozoic-Cenozoic closure of the Tethys Ocean, the collision between India and Asia beginning at ca. 50 Ma, and the tectonic evolution of the western Pacific Ocean.

During the past decade it has widely been accepted that the Avalonian-Cadomian belt results from Neoproterozoic to early Paleozoic Andean-type orogeny, that was active at the northern margin of Gondwana. The major imprints of this orogeny are recorded by so-called periGondwanan terranes which faced open oceans during the Neoproterozoic. Avalonianand Cadomian-type terranes show significant differences concerning the age of protoliths and the timing of accretion. Avalonian-type terranes developed from ca. 1 Ga old rocks and were subsequently accreted to the northern margin of West Gondwana (Amazonia). Cadomian-type terranes originated along the African margin by recycling ca. 2 Ga crust. In Paleozoic times the Avalonian-Cadomian belt fell into microplates that were detached from Gondwana and collided with Laurentia or Baltica. Several attempts have been made to reconstruct the Neoproterozoic-Early Paleozoic distribution of the peri-Gondwanan microplates relative to the West African and Amazonian Cratons. However, as robust paleomagnetic and other quantitative data are largely lacking, these reconstructions are still speculative and need further confirmation. The contributions of this special volume provide new data and models which help to improve our knowledge on the AvalonianCadomian orogeny. The papers are an outcome of the GEO 2002 meeting held during October 2002 in W rzburg, Germany. In an invited paper, Murphy et al. compare inferred relationships between peri-Gondwanan terranes and the northern Gondwanan margin with paleomagnetically constrained movements interpreted for the Amazonian and West African cratons for the interval ca. 800 – 500 Ma. The following eight papers deal with Cadomian events in the Bohemian Massif. A large number of new isotopic data is presented which helps to constrain the timing of orogenic events. The paper by Linnemann et al. represents new U-Pb SHRIMP ages of detrital and inherited zircons from pre-Variscan rocks of Saxo-Thuringia which reflect a West African provenance for sediments and magmatic rocks. Based on single zircon Pb-Pb evaporation and SHRIMP ages, combined with major and trace element data and Sm-Nd isotope systematics, Mingram et al., on the other hand, suggest a link between Saxo-Thuringia and Avalonia. They found evidence for at least two discrete magmatic events in the so-called red gneisses of the Erzgebirge. Patocka and torch elucidate Cadomian sediment provenances of the Early Paleozoic siliciclastic rocks of the Tepl -Barrandian unit, Bohemian Massif. The paper by Drost et al. presents new U-Pb-SHRIMP ages for the Cambrian volcanics of the Tepl -Barrandian unit and yields constraints on the late Neoproterozoic to Cambrian geotectonic settings. U-Pb and Pb-Pb ages obtained by Mazur et al. and by Zelazniewicz et al. indicate Neoproterozoic to Cambrian magmatism in different parts of the Sudetes (Bohemian Massif). Teipel et al. obtained new U-Pb SHRIMP and Nd isotopic data which suggest Upper Vendian and Lower Ordovician magmatism in the Bavarian Forest that is part of the Moldanubian unit. Friedl et al. derived new U-Pb zircon ages (SHRIMP and TIMS) from different orthogneisses of the Austrian part of the Bohemian Massif. They found evidence for both Neoproterozoic and Ordovician magmatism in the Moldanubian domain, the latter is interW. D rr Institut f r Geowissenschaften und Lithosph renforschung, Universit t Giessen, Senckenbergstr. 3, 35390 Giesen, Germany

Research Article| September 01, 2015 Late Paleozoic Woniusi basaltic province from Sibumasu terrane: Implications for the breakup of eastern Gondwana's northern margin Shi-Yong Liao; Shi-Yong Liao † 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China2Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China †E-mail: liaosy@hotmail.com or syliao@pmo.ac.cn. Search for other works by this author on: GSW Google Scholar Dong-Bing Wang; Dong-Bing Wang 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar Yuan Tang; Yuan Tang 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar Fu-Guang Yin; Fu-Guang Yin 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar Shu-Nan Cao; Shu-Nan Cao 3Department of Earth Sciences, University of Hong Kong, Hong Kong, China Search for other works by this author on: GSW Google Scholar Li-Quan Wang; Li-Quan Wang 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar Bao-Di Wang; Bao-Di Wang 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar Zhi-Ming Sun Zhi-Ming Sun 1Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2015) 127 (9-10): 1313–1330. https://doi.org/10.1130/B31210.1 Article history received: 20 Sep 2014 rev-recd: 30 Jan 2015 accepted: 02 Mar 2015 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Shi-Yong Liao, Dong-Bing Wang, Yuan Tang, Fu-Guang Yin, Shu-Nan Cao, Li-Quan Wang, Bao-Di Wang, Zhi-Ming Sun; Late Paleozoic Woniusi basaltic province from Sibumasu terrane: Implications for the breakup of eastern Gondwana's northern margin. GSA Bulletin 2015;; 127 (9-10): 1313–1330. doi: https://doi.org/10.1130/B31210.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The tectonic mechanism responsible for detachment of the Sibumasu terrane in the eastern Cimmerian continent from the Australian Gondwana margin remains poorly understood and debated. Our study on the late Paleozoic Woniusi basaltic province in the northern Sibumasu terrane may provide a new perspective on this problem, and further, on the rifting dynamics of eastern Gondwana's northern margin. In this study, we revealed that the Woniusi basaltic province is spread over an area of ∼12,000 km2 with a thickness of ∼300–500 m for the eruptive phase. Direct zircon U-Pb dating of mafic dikes indicates that the Woniusi basaltic province was emplaced between the latest Carboniferous and late Early Permian (301 Ma to 282 Ma), synchronous with basaltic rocks from the Panjal Traps, Tethyan Himalaya (Bhote Kosi, Selong, Abor), Lhasa, and southern Qiangtang. Geochemically, the Woniusi basaltic rocks show subalkaline tholeiitic affinity and relatively homogeneous features of enriched light rare earth elements (LREEs) and large ion lithophile elements (LILEs) but depleted Nb and Ta patterns. They were most likely derived from an enriched subcontinental lithospheric mantle source and triggered by the mantle plume–induced rifting process. The Woniusi basaltic province, together with other coeval basaltic provinces from the Panjal Traps, Tethyan Himalaya, Lhasa, and southern Qiangtang, belongs to a fragmented large igneous province that may have had an original area of over 2 × 106 km2, which is comparable to that of the Ontong-Java, Deccan, or Siberian Traps. These Tethyan basaltic provinces share a common mantle plume centered in northern Greater India. It was this mantle plume that may have triggered the initial rifting of the eastern Cimmerian terranes (e.g., Sibumasu, southern Qiangtang) from both the northern Indian and Australian Gondwana margins, as well as the opening of Meso-Tethys Ocean. This study, moreover, sheds light on the paleopositions of the Lhasa and Tengchong terranes before their breakups. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Austroalpine basement in the eastern Alps underwent Proto-Tethys and Paleo-Tethys tectonic evolution. To restore the tectonic processes of Proto-Paleo-Tethys Ocean in the eastern Alps, we carried out a systematic study by U-Pb zircon geochronology and geochemistry. In the Schladming Complex our study shows that the granodioritic gneisses (539-538 Ma) with A2-type geochemical signature and the fine-grained amphibolite (531 Ma) with E-MORB affinity, represent a bimodal magmatism. A medium-grained amphibolite (495 Ma) exhibits OIB-like geochemical features. The monzonite granitic gneiss (464 Ma) and plagioclase gneiss (487 Ma) have volcanic arc geochemical features. In Speik-Gleinalpe Complex the amphibolites (489-496 Ma), granitic gneiss (491 Ma) and plagiogneiss (472-476 Ma) all have subduction-related geochemical signatures. These all magmatism recorded the subduction and back-arc basin tectonic processes of Proto-Tethys Ocean.In Schladming Complex we found that the overgrowth rims of zircons of the early Paleozoic biotite-plagioclase gneiss and granitic gneisses give a dominantly metamorphic age of ca. 355 Ma. In addition, the zircons from the samples of Speik-Gleinalpe also yield a metamorphic age of ca. 400 Ma. In the Schladming Complex we also dated two granites with crystallization age of 353-355 Ma, which have subduction-related geochemical characteristics. These Devonian-Carboniferous metamorphism and magmatism together indicate that the Austroalpine basement had been overprinted by the Variscan orogeny.In the southern and western Saualpe crystalline basement, the three amphibolites yield crystallization ages of 415-418 Ma and have similar geochemical signature of OIB. We suggest that the Late Silurian-earliest Devonian OIB-like magmatism was related to a back-arc extension setting along the northern margin of Gondwana and indicating the opening of the Paleo-Tethys Ocean.In the Plankogel Complex we found two N-MORB amphibolites exhibit late Permian/Early Triassic protolith ages (254-227 Ma), representing the Paleo-Tethys oceanic crust relics. The manganese quartzites are explained as siliceous deep-sea sediments with a large Permian to Early Triassic (244-282 Ma) volcanic components. We interpret the Plankogel Complex as an ophiolitic complex of Paleo-Tethys suture. Based on our studies above we restore the tectonic evolution of Proto-Paleo-Tethys Ocean in the eastern Alps: The basement complexes in the eastern Alps had been a part of the active continental margin of Gondwana. With the subduction of the Proto-Tethys oceanic plate to the south, a back-arc rift developed along the northern margin of the Gondwana in the Early Cambrian, resulted in the opening of a back-arc basin (Speik Ocean) and the break-off of the proto-E Alps terranes from Gondwana in the Late Cambrian. In the Early Ordovician the proto-E Alps terranes collided back to the Gondwana with the closure of Speik Ocean. During the Late Silurian-earliest Devonian the Paleo-Tethys Ocean opened as back-arc basin due to southward subduction of Rheic Ocean, resulting in the break-off of the proto-south-Europe marginal terranes from the northern margin of Gondwana. From Late Devonian to Early Carboniferous the break-off terranes drifted northward and accreted to the southern margin of European continent with the consuming and closure of Rheic Ocean. In the Late Permian-Middle Triassic the Paleo-Tethys Ocean was closed after continuing northward subduction.

Diagenetic history and provenance of Devonian terrestrial sandstones at the margin of Gondwana: Padeha Formation, Eastern Alborz, Iran

Understanding the evolution and destruction of past oceans not only leads to a better understanding of earth history, but permits comparison with extant ocean basins and tectonic processes. This paper reviews the history of the Early Paleozoic circum‐Atlantic oceans by analogy with the Pacific Ocean and Mesozoic Tethys. Rifting and continental separation from 620 to 570 Ma led to the development of passive margins along parts of the northern margin of Gondwana (the western coast of South America); eastern Laurentia (eastern North America, NW Scotland and East Greenland), and western Baltica (western Scandinavia). Meagre paleomagnetic data suggest that western South America and eastern North America could have been joined together to form facing margins after breakup. Although western Baltica is an apparently obvious candidate for the margin facing NW Scotland and East Greenland, the paleomagnetic uncertainties are so large that other fragments could have been positioned there instead. The Iapetus Ocean off northeastern Gondwana was probably a relatively wide Pacific‐type ocean with, during the late Precambrian to early Ordovician, the northern margin of Gondwana as a site of continentward‐dipping subduction zone(s). The 650‐500 Ma arc‐related igneous activity here and the associated deformation gave rise to the Cadomian, ‘Grampian’, Penobscotian, and Famantinian igneous and orogenic events. By 490‐470 Ma, marginal basins had formed along the eastern Laurentian margin as far as NE Scotland, along parts of the northern margin of Gondwana, and off western Baltica, but none are known from the East Greenland margin. These basins closed and parts were emplaced as ophiolites shortly after their formation by processes that, at least in some cases, closely resemble the emplacement of the late Cretaceous Semail ophiolite of Oman. This orogenic phase seems to have involved collision and attempted subduction of the continental margin of Laurentia, Gondwana and Baltica. In Baltica it gave rise to some eclogite facies metamorphism. Marginal basin development may have been preceded by arc formation as early as ca 510 Ma. A double arc system evolved outboard from the eastern Laurentian and western Baltica margins, analogous to some of the arc systems in the present‐day western Pacific. At 480‐470 Ma, there was a second phase of breakup of Gondwana, affecting the active Gondwanan margin. Eastern and Western Avalonia, the Carolina Slate Belt, Piedmont, and other North American exotic continental blocks rifted away from Gondwana. Farther east, Armorica, Aquitainia, Iberia and several European exotic continental blocks also rifted away, though it is unlikely that they all rifted at the same time. Between 460‐430 Ma, peaking at ca 450 Ma, orogenic events involved continuing arc‐continent collision(s). From 435‐400 Ma the remaining parts of the Eastern Iapetus Ocean were destroyed and the collision of Baltica with Laurentia caused the 430‐400 Ma Scandian orogeny, followed by suturing of these continents during the Siluro‐Devonian Acadian orogeny or Late Caledonian orogeny to 380 Ma, leaving a smaller but new ocean south of the fragments that had collided with the Laurentian margin farther south. The Ligerian orogeny 390‐370 Ma collision of Gondwana‐derived Aquitaine‐Cantabrian blocks with Eastern Avalonia‐Baltica and removed the part of the Iapetus south of Baltica.Prior to any orogenic events, the Eastern Iapetus Ocean between Baltica and Laurentia may have resembled the present‐day central Atlantic Ocean between Africa and North America. The ocean appears to have closed asymmetrically, with arcs forming first outboard of the western margin of Baltica while the East Greenland margin was unaffected. The Western Iapetus Ocean between Laurentia and Gondwana also closed asymmetrically with a dual arc system developing off Laurentia and an arc system forming off the northern margin of Gondwana. Like the Pacific Ocean today, the Eastern Iapetus Ocean had a longer and more complex history than the Western Iapetus Ocean: it was already in existence at 560 Ma, probably developed over at least 400 million years, by mid‐Cambrian time was many thousands of kilometres wide at maximum extent, and was associated with a < 30 million year phase of marginal basin formation. In contrast, the Western Iapetus Ocean appears to have been much narrower, shorter lived (probably < 100 million years), and associated with the rifting to form two opposing passive carbonate margins, analogous to the Mesozoic Tethys or the present‐day Mediterranean.

Numerous K-bentonites from the Ordovician–Silurian (O–S) transition in South China record important information about the geodynamics of volcanic activity in the northern margin of Gondwana. A series of K-bentonite beds have been identified in the Zhoujiaxi Group (Early Silurian) in foreland basins from central Hunan Province, China. They are dominantly composed of illite with minor kaolinite. Volcanogenic minerals include quartz, feldspar, biotite, and lesser apatite and zircon. U–Pb zircon ages from three beds, 442.8 ± 1.8, 442.2 ± 1.9 and 441.6 ± 2.0 Ma are compatible with the age of the O–S global boundary. Geochemical results indicate calc-alkaline felsic magmas derived from continental crust and erupted in a subduction-related collisional environment. Isopach schemes and grain size reveal that the volcanic ashes were sourced from a volcanic event likely with a volcanic explosivity index of 8, and transported 300 – 1000 km away from the palaeo SSE. The volcanism was associated with northwestern subduction of the Zhenghe-Dapu Ocean beneath the southeastern South China Block (SCB) on the northern margin of Gondwana. The Zhenghe-Dapu fault might be a suture zone, implying the consumption of the Zhenghe-Dapu Ocean during collision between the Nanhai terrane and the SCB. This study supports that the Wuyi-Yunkai Orogenic Belt is a collision-type orogen rather than an intraplate belt. Supplementary material: Plots and geochemical data are available at https://doi.org/10.6084/m9.figshare.c.5027096

The Proto-Tethys Ocean played an important role in the formation and evolution of the East Asian continental blocks, and the final closure of the Proto-Tethys Ocean may have led to the first assembly of nearly all East Asian blocks at the northern margin of Gondwana. However, controversy remains about the reconstruction of East Asian blocks at the northern margin of Gondwana. The Tibetan Plateau is located in the northern margin of Gondwana and recorded the entire tectonic evolution from continental rift and drift to subduction and collision during the early Paleozoic. Therefore, it is an important region in which to address tectonic evolution processes of the Proto-Tethys Ocean and Gondwana. Here, we present petrology, zircon U-Pb, Sr-Nd-Hf isotope, and whole-rock geochemical data from newly recognized intermediate-mafic magmatic rocks from the Amdo microcontinent of central Tibet, with a view to gain insights into the nature and geotectonic evolution of the northern margin of Gondwana. Zircon grains from meta-andesites and meta-basites in Amdo yielded magmatic crystallization ages of 490 Ma and 455−450 Ma, respectively. The meta-andesites are characterized by enrichment in large ion lithophile elements (e.g., Rb, Th, U, and K) and depletion in high field strength elements (e.g., Nb, Ta, and Ti) with positive zircon εHf(t) values (+3.4 to +6.4), which were probably derived from partial melting of a depleted mantle source enriched by minor fluids from subducted sediments in a continental arc setting. The meta-basites are tholeiitic and exhibit both mid-ocean-ridge basalt (e.g., flat rare earth element patterns) and arc-like (e.g., elevated Th/Yb ratios) geochemical affinities, in combination with negative zircon εHf(t) (−4.6 to −0.3) and whole-rock εNd(t) (−0.21 to −0.45) values, suggesting that they were probably generated by varying degrees of partial melting of a spinel peridotite source with ∼5%−10% crustal assimilation in a back-arc setting. In this regard, we favor the interpretation that the Amdo microcontinent experienced long-lasting (ca. 530−450 Ma) subduction of the Proto-Tethys Ocean slab before the subsequent collisional accretion of microcontinents. Integrating results from previous studies, we propose that the Amdo microcontinent, South Qiangtang terrane, Qilian-Qaidam terrane, and other East Asian blocks were all located at the northern margin of East Gondwana, which recorded the arc-related magmatism along the proto-Tethyan margin in the early Paleozoic. The closure of the Proto-Tethys Ocean and initial collision along the East Gondwana Proto-Tethyan margin may have been diachronous between ca. 455 and 430 Ma.

The process and mechanism of continuous rifting and drifting along the northern margin of Gondwana remain a cutting-edge yet controversial topic in modern Earth sciences. In this study, we analysed the geochronology, geochemistry, Lu–Hf isotopes, and Sr–Nd isotopes of Late Triassic high-Mg adakite-like andesites, trachyandesites, rhyolites, and OIB-type basalts from the Pasha area in the southern Yarlung Zangbo Suture Zone, Tibet. By integrating these results with previously published data on Late Triassic magmatism in southern Tibet, we establish a magmatic sequence consisting of early (~234 Ma) arc-related magmatism and late (~225 Ma) rift-related magmatism. This sequence demonstrates that Late Triassic rifting along the northern margin of Gondwana was controlled by subduction processes: initial southward subduction and the subsequent development of a back-arc basin progressively weakened the continental margin, while mantle convection associated with slab rollback triggered the rifting and northward drift of this margin. Building on these results and integrating previous findings on Early Permian and Middle Triassic rifting, we propose that both slab pull and oceanic crust subduction contributed to repeated continental-margin rifting. Specifically, Early Permian and Middle Triassic rifting events were mainly driven by plate pull, enhanced by the influence of the mantle plume, whereas Late Triassic rifting was dominated by slab subduction and initiated by slab rollback. This study provides new geological evidence supporting subduction-controlled rifting along the northern margin of Gondwana, addressing the long-standing lack of direct evidence for this mechanism.

Carboniferous paleogeographic, phytogeographic, and paleoclimatic reconstructions

Locating northern Qiangtang on the margin of Gondwana or Laurasia? Evidence from detrital zircon geochronology

Cambrian-Ordovician continental magmatic arc at the northern margin of Gondwana: Insights from the Schladming Complex, Eastern Alps

Reconstruction of Tournaisian-Viséan tectonic and climatically induced event histories of the Mobarak carbonate platform along depositional strike in the northeastern margin of Gondwana: Constraints from high-resolution cycle and sequence stratigraphy

Petrogenesis of early Paleozoic peraluminous granite in the Sibumasu Block of SW Yunnan and diachronous accretionary orogenesis along the northern margin of Gondwana