Showing papers on "Gondwana published in 2015"
TL;DR: The ChahJam-Biarjmand complex (CJBC) as mentioned in this paper contains granitic to tonalitic orthogneissic rocks (old plutons) and associated metasediments, amphibolites and paragneisses.
161 citations
TL;DR: Recon reconstructions of ocean circulation show that massive reorganization and homogenization of Southern Ocean water masses coincided with migration of the northern margin of the Tasmanian Gateway into the mid-latitude westerly wind band, which is reconstructed at 64° S, near to the northernmargin.
Abstract: Neodymium isotopes from fossil fish teeth and tectonic reconstructions show that the deep Tasmanian Gateway opened up about 33 million years ago and that the Antarctic Circumpolar Current arose 30 million years ago, when the gateway probably moved into the latitudes of the strong westerly winds. Ocean circulations were transformed during the Oligocene, when a series of tectonic movements reshaped the continents into a pattern that began to resemble what we see today. In particular the Drake Passage (between South America and Antarctica) and the Tasmanian Gateway (between Australia and Antarctica) opened and provided channels for the Antarctic Circumpolar Current. The sequence and timing of these events are uncertain. Here Howie Scher et al. use neodymium isotopes extracted from fossilized fish teeth as well as tectonic reconstructions to show that the deep Tasmanian Gateway opened up about 33 million years ago, and that the Antarctic Circumpolar Current arose 3 million years later, when the gateway probably moved into the latitudes of the strong westerly winds. Earth’s mightiest ocean current, the Antarctic Circumpolar Current (ACC), regulates the exchange of heat and carbon between the ocean and the atmosphere1, and influences vertical ocean structure, deep-water production2 and the global distribution of nutrients and chemical tracers3. The eastward-flowing ACC occupies a unique circumglobal pathway in the Southern Ocean that was enabled by the tectonic opening of key oceanic gateways during the break-up of Gondwana (for example, by the opening of the Tasmanian Gateway, which connects the Indian and Pacific oceans). Although the ACC is a key component of Earth’s present and past climate system1, the timing of the appearance of diagnostic features of the ACC (for example, low zonal gradients in water-mass tracer fields4,5,6,7) is poorly known and represents a fundamental gap in our understanding of Earth history. Here we show, using geophysically determined positions of continent–ocean boundaries8, that the deep Tasmanian Gateway opened 33.5 ± 1.5 million years ago (the errors indicate uncertainty in the boundary positions). Following this opening, sediments from Indian and Pacific cores recorded Pacific-type neodymium isotope ratios, revealing deep westward flow equivalent to the present-day Antarctic Slope Current. We observe onset of the ACC at around 30 million years ago, when Southern Ocean neodymium isotopes record a permanent shift to modern Indian–Atlantic ratios. Our reconstructions of ocean circulation show that massive reorganization and homogenization of Southern Ocean water masses coincided with migration of the northern margin of the Tasmanian Gateway into the mid-latitude westerly wind band, which we reconstruct at 64° S, near to the northern margin. Onset of the ACC about 30 million years ago coincided with major changes in global ocean circulation9 and probably contributed to the lower atmospheric carbon dioxide levels that appear after this time10.
157 citations
TL;DR: In this article, the granitic intrusions in the central part of the Jiamusi-Khanka Massif in the eastern segment of the Central Asian Orogenic Belt (CAOB) were investigated.
154 citations
TL;DR: A 3D S-velocity model for the Antarctic lithosphere was constructed using a single-step surface wave tomographic method, and a Moho depth map was estimated from the model using the derived crustal thicknesses, the average ratio of lithospheric mantle and crustal densities of Antarctica was calculated as mentioned in this paper.
Abstract: Since 2007/2008, seismographs were deployed in many new locations across much of Antarctica Using the records from 122 broadband seismic stations, over 10,000 Rayleigh wave fundamental-mode dispersion curves have been retrieved from earthquake waveforms and from ambient noise Using the processed data set, a 3-D S-velocity model for the Antarctic lithosphere was constructed using a single-step surface wave tomographic method, and a Moho depth map was estimated from the model Using the derived crustal thicknesses, the average ratio of lithospheric mantle and crustal densities of Antarctica was calculated The calculated density ratio indicates that the average crustal density for Antarctica is much higher than the average values for continental crust or the average density of lithospheric mantle is so low as to be equal to low-density bound of Archean lithosphere The latter implies that the lithospheric mantle in much of Antarctica should be old and of Archean age The East Antarctic Mountain Ranges (EAMOR) represent a thick crustal belt, with the thickest crust (~60 km) located close to Dome A Very high velocities can be found at depths greater than 200 km beneath parts of East Antarctica, demonstrating that the continental lithosphere extends deeper than 200 km The very thick crust beneath the EAMOR may represent the collision suture of East Gondwana with Indo-Antarctica and West Gondwana during the Pan-African orogeny
144 citations
TL;DR: The intermediate to acid Choiyoi Magmatic Province is the most conspicuous feature along the Late Paleozic continental margin of southwestern Gondwana, and is generally regarded as the possible source for the widespread ash fall deposits interlayered with sedimentary sequences in the adjacent gondwana basins as mentioned in this paper.
134 citations
Abstract: A detrital zircon U-Pb and Lu-Hf isotopic study was carried out in the Middle Silurian to Late Carboniferous sedimentary strata of the northwestern Tarim Craton in order to understand accretionary processes in the southern part of the Central Asian Orogenic Belt. Detrital zircons from these strata yielded U-Pb ages clustering around 2.8–2.3 Ga, 2.0–1.7 Ga, 1.3–0.9 Ga, 880–600 Ma, and 500–400 Ma, with age populations and Hf isotopic signatures matching those of magmatic rocks in the Tarim Craton and the Central Tianshan Block. Abundant 500–400 Ma detrital zircons most likely reflect deposition in a retroarc foreland basin inboard of an Andean-type magmatic arc to the north, supporting the northern Tarim-Central Tianshan connection during early Paleozoic time. The absence of 380–310 Ma zircon population in the Carboniferous siliciclastic rocks suggests that the Central Tianshan Block may have been separated from the Tarim Craton in the Early Devonian, caused by the interarc/back-arc opening of the South Tianshan Ocean. We propose an accretionary orogenic model switching from advancing to retreating mode during Paleozoic time in the southwestern part of the Paleo-Asian Ocean. This transition most likely occurred coevally with the rifting of Southeast Asian blocks from the northeastern margin of Gondwana.
133 citations
TL;DR: In tectonic maps of Variscan Europe, allochthonous pieces of Cadomian basement clearly stand out with their predominant metabasic to ultrabasic elements, the so-called exotic terranes with ophiolites as discussed by the authors.
Abstract: In tectonic maps of Variscan Europe, allochthonous pieces of Cadomian basement clearly stand out with their predominant metabasic to ultrabasic elements, the so-called exotic terranes with ophiolites. Most of these domains are observed in basements of the Central Iberian Allochthone, the South Armorican domain, the nappe structures of the French Massif Central, the Saxothuringian Zone and the Bohemian Massif. Similar relics can be recognized in many Alpine basement areas, and correlations with supposedly more autochthonous basements, such as the Ossa Morena Zone and the Central Iberian basement, can be envisaged. All of these relics are thought to represent the interrupted trace of a former continuous or discontinuous structure, characterized by the presence of ocean-derived proto-Rheic rock suites. These can be interpreted as pieces of former magmatic arcs of Ediacaran to Cambrian age accreted to the Gondwana margin, which later were scattered as allochthonous units during the Variscan plate-tectonic processes. The presence of similar rock suites of Ordovician age in the Alpine realm is explained by the accretion of exotic China-derived basements and their collision with the Gondwana margin during the opening of the Rheic Ocean.
119 citations
TL;DR: A review of the current state of knowledge on the coquina play can be found in this paper, where the authors provide an integrated discussion of the state-of-the-art on the Coquina Play.
111 citations
TL;DR: The Precambrian geological history of Peninsular India covers nearly 3.0 Ga as discussed by the authors, and it appears that basin formation and subsequent closure can be grossly constrained to three separate intervals that also broadly correspond to the assembly and disaggregation of the supercontinents Columbia, Rodinia and Gondwana.
Abstract: The Precambrian geological history of Peninsular India covers nearly 3.0 Ga. The Peninsula is an assembly of five different cratonic nuclei known as the Aravalli–Bundelkhand, Eastern Dharwar, Western Dharwar, Bastar and Singhbhum cratons along with the Southern Granulite Province. Final amalgamation of these elements occurred either by the end of the Archaean (2.5 Ga) or by the end of the Palaeoproterozoic ( c. 1.6 Ga). Each of these nuclei contains one or more sedimentary basins (or metasedimentary basins) of Proterozoic age. This chapter provides an overview of each of the cratons and a brief description of the Precambrian sedimentary basins in India that form the focus of the remainder of this book. In our view, it appears that basin formation and subsequent closure can be grossly constrained to three separate intervals that also broadly correspond to the assembly and disaggregation of the supercontinents Columbia, Rodinia and Gondwana. The oldest Purana-I basins developed during the 2.5–1.6 Ga interval, Purana-II basins formed during the 1.6–1.0 Ga interval and the Purana-III basins formed during the Neoproterozoic–Cambrian interval.
95 citations
TL;DR: In this article, the authors presented a new tectonic model for the evolution of NW Indian Ocean Subducted slab under the Carlsberg Ridge resulted from Arabia-India convergence.
Abstract: Gondwana breakup since the Jurassic and the northward motion of India toward Eurasia were associated with formation of ocean basins and ophiolite obduction between and onto the Indian and Arabian margins. Here we reconcile marine geophysical data from preserved oceanic basins with the age and location of ophiolites in NW India and SE Arabia and seismic tomography of the mantle below the NW Indian Ocean. The North Somali and proto-Owen basins formed due to 160-133-Ma N-S extension between India and Somalia. Subsequent convergence destroyed part of this crust, simultaneous with the uplift of the Masirah ophiolites. Most of the preserved crust in the Owen Basin may have formed between 84 and 74-Ma, whereas the Mascarene and the Amirante basins accommodated motion between India and Madagascar/East Africa between 85 and circa 60-Ma and 75 and circa 66-Ma, respectively. Between circa 84 and 45-Ma, oblique Arabia-India convergence culminated in ophiolite obduction onto SE Arabia and NW India and formed the Carlsberg slab in the lower mantle below the NW Indian Ocean. The NNE-SSW oriented slab may explain the anomalous bathymetry in the NW Indian Ocean and may be considered a paleolongitudinal constraint for absolute plate motion. NW India-Asia collision occurred at circa 20-Ma deforming the Sulaiman ranges or at 30-Ma if the Hindu Kush slab north of the Afghan block reflects intra-Asian subduction. Our study highlights that the NW India ophiolites have no relationship with India-Asia motion or collision but result from relative India-Africa/Arabia motions instead. Key Points We present a new tectonic model for the evolution of NW Indian Ocean Subducted slab under the Carlsberg Ridge resulted from Arabia-India convergence
94 citations
TL;DR: Early Ordovician granites are comparable to those of high-K, calc-alkaline S-type granites and they exhibit negative values of zircon eHf(t) (−8.5 to + 1.7) and whole-rock eNd(t), as well as old zirccon Hf model ages (TCDM = 1349-1992 ǫ and wholerock Nd model ages(TCDM= 1145-1804 ).
TL;DR: In this article, the authors reviewed the allochthonous terrane accretion model for the geological development of the Antarctic Peninsula continental margin arc and reinterpreted the geology as having evolved as an in situ continental arc.
Abstract: The allochthonous terrane accretion model previously proposed for the geological development of the Antarctic Peninsula continental margin arc is reviewed in light of recent data and the geology is reinterpreted as having evolved as an in situ continental arc. This is based upon the following factors: (1) the presence of Early Palaeozoic basement and stratigraphic correlation of sequences between the autochthonous and previously proposed allochthonous terranes; (2) isotopic evidence for similar deep crustal structure across the different terranes; (3) ocean island basalt magmas and deep marine sedimentary rocks formed during continental margin extension within the previously proposed accretionary wedge sequence (i.e. not formed against an active oceanic arc); (4) the distribution of magnetic susceptibility measurements and aeromagnetic data locating the palaeo-subduction zone along the west of the Peninsula; (5) a lack of clear palaeomagnetic distinction between the terranes. The following alternative tectonic history is proposed: (1) amalgamation and persistence of Gondwana; (2) subsequent silicic large igneous province magmatism and extension; (3) development and history of Andean subduction until its cessation in the Cenozoic. A number of features in the Antarctic Peninsula correlate with those of other circum-Pacific margins, supporting a global evaluation of allochthonous v. autochthonous margin development to aid our understanding of crustal growth mechanisms.
TL;DR: The Southern Granulite Terrane in southern India preserves evidence for regional-scale high to ultra-high temperature metamorphism related to the amalgamation of the supercontinent Gondwana as mentioned in this paper.
TL;DR: In this paper, the authors reported Cambrian ultrapotassic felsic volcanics from the Lhasa terrane, which were derived from the partial melting of middle Proterozoic crustal rocks in the lower crust under high-temperature and water-absent conditions in an extensional environment of active magmatic arc.
TL;DR: The Toploje Member chert is a Roadian to Wordian autochthonous-parautochthonsous silicified peat preserved within the Lambert Graben, East Antarctica as mentioned in this paper, which preserves a remarkable sample of terrestrial life from high-latitude central Gondwana prior to the Capitanian mass extinction event from both mega- and microfossil evidence that includes cryptic components rarely seen in other fossil assemblages.
TL;DR: The Permian System of eastern Australia provides a unique record of this transition along a high-latitude, open marine shelf as discussed by the authors, and the record also spans temperate to polar palaeolatitudes, providing an opportunity to examine environmental changes along a latitudinal transect.
TL;DR: In this paper, the authors used two major databases for the last 2.5 Gyr: the timing and locations of collisional and accretionary orogens, and average plate velocities as deduced from paleomagnetic and paleogeographic data.
TL;DR: In this paper, the authors presented a new global tomographic image, which shows a slab-like structure with coherency from the upper mantle to the core-mantle boundary region, which they postulate is an ancient tectonic plate that sank into the mantle along an extensive intraoceanic subduction zone that migrated southwestward across the ancient Tethys Ocean in the Mesozoic Era.
Abstract: In this study, ancient subducted tectonic plates have been observed in past seismic images of the mantle beneath North America and Eurasia, and it is likely that other ancient slab structures have remained largely hidden, particularly in the seismic-data-limited regions beneath the vast oceans in the Southern Hemisphere. Here we present a new global tomographic image, which shows a slab-like structure beneath the southern Indian Ocean with coherency from the upper mantle to the core-mantle boundary region—a feature that has never been identified. We postulate that the structure is an ancient tectonic plate that sank into the mantle along an extensive intraoceanic subduction zone that migrated southwestward across the ancient Tethys Ocean in the Mesozoic Era. Slab material still trapped in the transition zone is positioned near the edge of East Gondwana at 140 Ma suggesting that subduction terminated near the margin of the ancient continent prior to breakup and subsequent dispersal of its subcontinents.
01 Jan 2015
TL;DR: The Ethiopian region records about one billion years of geological history as discussed by the authors, with the first event being the closure of the Mozambique ocean between West and East Gondwana with the development of the Ethiopian basement ranging in age from 880 to 550 Ma.
Abstract: The Ethiopian region records about one billion years of geological history. The first event was the closure of the Mozambique ocean between West and East Gondwana with the development of the Ethiopian basement ranging in age from 880 to 550 Ma. This folded and tilted Proterozoic basement underwent intense erosion, which lasted one hundred million years, and destroyed any relief of the Precambrian orogen. Ordovician to Silurian fluviatile sediments and Late Carboniferous to Early Permian glacial deposits were laid down above an Early Paleozoic planation surface. The beginning of the breakup of Gondwana gave rise to the Jurassic flooding of the Horn of Africa with a marine transgression from the Paleotethys and the Indian/Madagascar nascent ocean. After this Jurassic transgression and deposition of Cretaceous continental deposits, the Ethiopian region was an exposed land for a period of about seventy million years during which a new important peneplanation surface developed. Concomitant with the first phase of the rifting of the Afro/Arabian plate, a prolific outpouring of the trap flood basalts took place predominantly during the Oligocene over a peneplained land surface of modest elevation. In the northern Ethiopian plateau, huge Miocene shield volcanoes were superimposed on the flood basalts. Following the end of the Oligocene, the volcanism shifted toward the Afar depression, which was experiencing a progressive stretching, and successively moved between the southern Ethiopian plateau and the Somali plateau in correspondence with the formation of the Main Ethiopian Rift (MER). The detachment of the Danakil block and Arabian subcontinent from the Nubian plate resulted in steep marginal escarpments marked by flexure and elongated sedimentary basins. Additional basins developed in the Afar depression and MER in connection with new phases of stretching. Many of these basins have yielded human remains crucial for reconstructing the first stages of human evolution. A full triple junction was achieved in the Early Pliocene when the MER penetrated into the Afar region, where the Gulf of Aden and the Red Sea rifts were already moving toward a connection via the volcanic ranges of northern Afar. The present-day morphology of Ethiopia is linked to the formation of the Afar depression, MER, and Ethiopian plateaus. These events are linked to the impingement of one or more mantle plumes under the Afro-Arabian plate. The elevated topography of the Ethiopian plateaus is the result of profuse volcanic accumulation and successive uplift. This new highland structure brought about a reorganization of the East Africa river network and a drastic change in the atmospheric circulation.
TL;DR: The Tauride block in Turkey is a peri-Gondwana, Cadomian-type terrane that rifted from the Afro-Arabian margin of Gondwana in the Permo-Triassic and re-accreted to Arabia in the Neogene as mentioned in this paper.
TL;DR: In this paper, the authors conducted profile measurements, gravel composition analyses, and U-Pb dating on detrital zircons from a representative glacial marine diamictite in the Gangmaco-Dabure area of the Southern Qiangtang-Baoshan block, Tibetan Plateau.
TL;DR: In this article, the structure, age and petrogenesis of plutonic basement rocks from the Kuh-e-Sarhangi region, located in the Kashmar-Kerman tectonic zone of Central Iran are described.
TL;DR: In this paper, a simpler tectonic model involving continent (craton)-volcanic arc collisions in the Dom Feliciano and Brasilia belts that led to intracontinental crustal thickening of the adjacent thinned hinterland (Ribeira Belt) was proposed.
Abstract: In this study, we challenge the multiple collision model for the tectonic evolution of the Neoproterozoic Ribeira Belt in Southeastern Brazil. New U–Pb SHRIMP data reveal Palaeoproterozoic (2153 ± 15 Ma) and Cryogenian (783 ± 6 and 768 ± 8 Ma) granitic rocks in the Embu Domain, and detrital zircon data of metasedimentary units from the Embu and Costeiro domains suggest a coherent tectonic evolution for the whole Ribeira Belt. Rather than by multiple collisions, these data are best explained by a simpler tectonic model involving continent (craton)-volcanic arc collisions in the Dom Feliciano and Brasilia belts that led to intracontinental crustal thickening of the adjacent thinned hinterland (Ribeira Belt) at ~640–610 Ma, followed by widespread post-collisional magmatism and rift-related sedimentation at ~600–540 Ma. We suggest that intracontinental orogeny is a relevant process during supercontinent assembly, as illustrated here by the evolution of significant parts of the Brasiliano orogen.
TL;DR: In this paper, the authors describe the Permian-Lower Triassic sedimentary succession of South Pamir and the associated biota of conodonts, foraminifers and brachiopods.
TL;DR: In this article, the role of mantle plumes in the formation and disruption of supercontinents has been investigated with specific examples involving Columbia, Rodinia, and Gondwana.
TL;DR: In this article, the age distribution of detrital zircon U-Pb was found to correspond to the ages of prominent crustal components within the respective cratons.
TL;DR: Zhang et al. as mentioned in this paper reported in-situ U-Pb and Hf isotopic results of detrital zircons from sixteen Cambrian-Silurian siliciclastic samples across the Nanhua foreland basin, South China.
TL;DR: This article examined the relationship between the Cadomian-type peri-Gondwana blocks and West and North Africa and Arabia (WNA) and the sediments derived therefrom during the Neoproterozoic.
TL;DR: In this paper, the authors report a sequence of thick, well-preserved basaltic lavas interlayered with shallow marine dolomitic carbonates, mudstones and siltstones of the Zhulongguan Group, in the western segment of the North Qilian orogen, northwest China.
TL;DR: In this paper, the authors report the petrology of mafic magmatic suites and metamorphic units, together with zircon and monazite U-Pb ages from several key areas in Cathaysia.