The evolution of the Triassic-Jurassic Maliac oceanic lithosphere: insights from the supra-ophiolitic series of Othris (continental Greece)

AbstractMajor ophiolitic thrust sheets are widespread within the internal Hellenides, particularly in the Pelagonian domain (Greece and Albania). The ophiolitic sheets are notably well exposed in western Othris mountains of continental Greece. In that area, the structural stacking of oceanic nappes obducted in the Jurassic is particularly well constrained. New sedimentological and structural data from recently studied outcrops, together with new micro-paleontological data, allow to reconsider the architecture of the ophiolitic nappes and their evolution in the Othris mountains. Our new data set includes notably the description of a Mid-Late Jurassic sedimentary succession, from basal litharenites and radiolarites to syn-obduction mélange, on top of the uppermost Mega Isoma ophiolitic Unit. These results are crucial in the perspective of constraining the Jurassic contractional evolution of the Maliac Ocean from the beginning of the subduction and intra-oceanic obduction to the final obduction on the Pelagonian continental crust. Another major result concerns the dating of primary conformable series of Middle and Late Triassic age on top of the pillow-lavas of the Fourka unit. Since this lava unit, with MORB affinities, is one of the syn-obduction Jurassic nappes, we propose that this very large Fourka nappe represents the major reference unit of the initial (Triassic) Maliac oceanic crust.

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Origin and emplacement of an inferred late Jurassic subduction-accretion complex, Euboea, eastern Greece

Geological Magazine ◽

10.1017/s0016756800018021 ◽

1991 ◽

Vol 128 (1) ◽

pp. 27-41 ◽

Cited By ~ 27

Author(s):

A. H. F. Robertson

Keyword(s):

Shallow Water ◽

Subduction Zone ◽

Late Jurassic ◽

Carbonate Platform ◽

Accretionary Prism ◽

Oceanic Lithosphere ◽

Passive Margin ◽

Late Triassic ◽

Accretionary Complex ◽

Alkali Basalts

AbstractIn northern Euboea, central eastern Greece, an up to 3 km-thick polygenetic melange (Pagondas complex) is structurally interleaved between a Triassic–Jurassic carbonate platform (Pelagonian Zone) and an overriding harzburgitic ophiolite. The melange mainly comprises late Triassic shallow-water limestone and calciturbidites, radiolarites, Triassic–Jurassic tholeiites, alkaline basalts and minor andesites. The units concerned range from kilometre-sized thrust sheets, and detached blocks, to broken formation and structureless, or bedded matrix-supported conglomerates (diamictite). The melange includes remnants of Neotethyan oceanic lithosphere, overlain by radiolarites, hemipelagic carbonates and distal calciturbidites derived from a Mesozoic carbonate platform. Tholeiites were erupted at a Triassic–Jurassic spreading axis, whilst within-plate-type alkali basalts are interpreted mainly as seamounts. Kilometre-scale detached blocks of shallow-water coralline limestone are identified as collapsed atolls, formed within an ocean and/or along the rifted continental margin. Volcaniclastic sediments are locally interbedded with radiolarite, and reflect post-volcanic erosion of the ocean floor. Intra-oceanic convergence began, apparently in late early Jurassic time, giving rise to the Euboea ophiolite above an inferred westwards-dipping subduction zone. The Pagondas Complex then developed as an accretionary prism. The subduction trench later collided with the Pelagonian passive margin, driving the hot Euobea ophiolite over the accretionary complex, to produce amphibolites and greenschists of the metamorphic sole. Trench–margin collision then drove the entire supra-subduction zone complex, apparently eastwards, downflexing the Pelagonian carbonate platform to form a foredeep in which late Jurassic (Kimmeridgian–Tithonian) radiolarian sediments accumulated. During emplacement, the accretionary complex was disrupted and partly resedimented as debris flows, turbiditic volcaniclastic sandstone and shale in a foredeep, or foreland basin setting.

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Late Norian (Late Triassic) Radiolarian assemblages from chert pebbles of the Pentalofos Formation (Mesohellenic basin, Greece). Palaeogeographic implications

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.185.2.115 ◽

2014 ◽

Vol 185 (2) ◽

pp. 115-122 ◽

Cited By ~ 6

Author(s):

Nikita Bragin ◽

Taniel Danelian ◽

Frank Chanier

Keyword(s):

Continental Crust ◽

Continental Margin ◽

Late Miocene ◽

Late Jurassic ◽

Late Triassic ◽

Radiolarian Chert ◽

Lower Miocene ◽

Radiolarian Assemblages

Abstract Well-preserved Late Norian Radiolaria were extracted from two pebbles of radiolarian chert included in Lower Miocene conglomerates of the Pentalofos Formation, in the area of Meteora (Mesohellenic basin, Greece). Both samples yielded a similar assemblage characterized by the presence of species Betraccium deweveri PESSAGNO & BLOME, Bipedis acrostylus BRAGIN, Pylostephanidium ankaraense BRAGIN & TEKIN and several other taxa typical of the Betraccium deweveri zone (uppermost Norian). This is the first evidence of Upper Norian radiolarian cherts from Greece. It is likely that the studied chert pebbles were derived from ophiolitic complexes or distal continental margin series situated to the east of the Mesohellenic basin; they were part of the Upper Norian oceanic realm that was obducted, during the Late Jurassic, over the Pelagonian continental crust. During the Late Miocene they were still present east of Meteora and they have been eroded since.

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Regularization and datuming of seismic data by weighted, damped least squares

Geophysics ◽

10.1190/1.2235616 ◽

2006 ◽

Vol 71 (5) ◽

pp. U67-U76 ◽

Cited By ~ 7

Author(s):

Robert J. Ferguson

Keyword(s):

Least Squares ◽

Seismic Data ◽

Synthetic Data ◽

Real Data ◽

Structural Data ◽

Irregular Sampling ◽

Data Set ◽

Near Surface ◽

Damped Least Squares ◽

Wavefield Extrapolation

The possibility of improving regularization/datuming of seismic data is investigated by treating wavefield extrapolation as an inversion problem. Weighted, damped least squares is then used to produce the regularized/datumed wavefield. Regularization/datuming is extremely costly because of computing the Hessian, so an efficient approximation is introduced. Approximation is achieved by computing a limited number of diagonals in the operators involved. Real and synthetic data examples demonstrate the utility of this approach. For synthetic data, regularization/datuming is demonstrated for large extrapolation distances using a highly irregular recording array. Without approximation, regularization/datuming returns a regularized wavefield with reduced operator artifacts when compared to a nonregularizing method such as generalized phase shift plus interpolation (PSPI). Approximate regularization/datuming returns a regularized wavefield for approximately two orders of magnitude less in cost; but it is dip limited, though in a controllable way, compared to the full method. The Foothills structural data set, a freely available data set from the Rocky Mountains of Canada, demonstrates application to real data. The data have highly irregular sampling along the shot coordinate, and they suffer from significant near-surface effects. Approximate regularization/datuming returns common receiver data that are superior in appearance compared to conventional datuming.

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The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton

Journal of Geodynamics ◽

10.1016/j.jog.2009.11.007 ◽

2010 ◽

Vol 50 (3-4) ◽

pp. 318-324 ◽

Cited By ~ 40

Author(s):

Guiting Hou ◽

Yanxin Wang ◽

K.R. Hari

Keyword(s):

North China Craton ◽

Late Jurassic ◽

North China ◽

Stress Fields ◽

Late Triassic

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The petrological and geochemical study of granitoid rocks from Mashhad area, Iran: Evidence for the Late Triassic Collisional Belt Northeast of Iran

10.5194/egusphere-egu21-6494 ◽

2021 ◽

Author(s):

Banafsheh Vahdati ◽

Seyed Ahmad Mazaheri

Keyword(s):

Subduction Zones ◽

Tectonic Setting ◽

Crustal Contamination ◽

Oceanic Lithosphere ◽

Late Triassic ◽

Common Belief ◽

Thrust Tectonics ◽

Wide Range ◽

Lree Enrichment ◽

Granitoid Rocks

Mashhad granitoid complex is part of the northern slope of the Binalood Structural Zone (BSZ), Northeast of Iran, which is composed of granitoids and metamorphic rocks. This research presents new petrological and geochemical whole-rock major and trace elements analyses in order to determine the origin of granitoid rocks from Mashhad area. Field and petrographic observations indicate that these granitoid rocks have a wide range of lithological compositions and they are categorized into intermediate to felsic intrusive rocks (SiO2: 57.62-74.39 Wt.%). Qartzdiorite, tonalite, granodiorite and monzogranite are common granitoids with intrusive pegmatite and aplitic dikes and veins intruding them. Based on geochemical analyses, the granitoid rocks are calc-alkaline in nature and they are mostly peraluminous. On geochemical variation diagrams (major and minor oxides versus silica) Na2O and K2O show a positive correlation with silica while Al2O3, TiO2, CaO, Fe2O3, and MgO show a negative trend. Therefore fractional crystallization played a considerable role in the evolution of Mashhad granitoids. Based on the spider diagrams, there are enrichments in LILE and depletion in HFSE. Low degrees of melting or crustal contamination may be responsible for LILE enrichment. Elements such as Pb, Sm, Dy and Rb are enriched, while Ba, Sr, Nd, Zr, P, Ti and Yb (in monzogranites) are all depleted. LREE enrichment and HREE depletion are observed in all samples on the Chondrite-normalized REE diagram. Similar trends may be evidence for the granitoids to have the same origin. Besides, LREE enrichment relative to HREE in some samples can indicate the presence of garnet in their source rock. Negative anomalies of Eu and Yb are observed in monzogranites. Our results show that Mashhad granitoid rocks are orogenic related and tectonic discrimination diagrams mostly indicate its syn-to-post collisional tectonic setting. No negative Nb anomaly compared with MORB seems to be an indication of non-subduction zone related magma formation. According to the theory of thrust tectonics of the Binalood region, the oceanic lithosphere of the Palo-Tethys has subducted under the Turan microplate. Since the Mashhad granitoid outcrops are settled on the Iranian plate, this is far from common belief that these granitoid rocks are related to the subduction zones and the continental arcs. The western Mashhad granitoids show more mafic characteristics and are possibly crystallized from a magma with sedimentary and igneous origin. Thus, Western granitoid outcrops in Mashhad are probably hybrid type and other granitoid rocks, S and SE Mashhad are S-type. Evidences suggest that these continental collision granitoid rocks are associated with the late stages of the collision between the Iranian and the Turan microplates during the Paleo-Tethys Ocean closure which occurred in the Late Triassic.

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Relative roles of source composition, fractional crystallization and crustal contamination in the petrogenesis of Andean volcanic rocks

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1984.0014 ◽

1984 ◽

Vol 310 (1514) ◽

pp. 675-692 ◽

Cited By ~ 114

Keyword(s):

Subduction Zone ◽

Continental Crust ◽

Fractional Crystallization ◽

Magma Mixing ◽

Volcanic Rocks ◽

Crustal Contamination ◽

Oceanic Lithosphere ◽

Alkaline Basalt ◽

Complex Process ◽

Heterogeneous Mantle

There are well established differences in the chemical and isotopic characteristics of the calc-alkaline basalt—andesite-dacite-rhyolite association of the northern (n.v.z.), central (c.v.z.) and southern volcanic zones (s.v.z.) of the South American Andes. Volcanic rocks of the alkaline basalt-trachyte association occur within and to the east of these active volcanic zones. The chemical and isotopic characteristics of the n.v.z. basaltic andesites and andesites and the s.v.z. basalts, basaltic andesites and andesites are consistent with derivation by fractional crystallization of basaltic parent magmas formed by partial melting of the asthenospheric mantle wedge containing components from subducted oceanic lithosphere. Conversely, the alkaline lavas are derived from basaltic parent magmas formed from mantle of ‘within-plate’ character. Recent basaltic andesites from the Cerro Galan volcanic centre to the SE of the c.v.z. are derived from mantle containing both subduction zone and within-plate components, and have experienced assimilation and fractional crystallization (a.f.c.) during uprise through the continental crust. The c.v.z. basaltic andesites are derived from mantle containing subduction-zone components, probably accompanied by a.f.c. within the continental crust. Some c.v.z. lavas and pyroclastic rocks show petrological and geochemical evidence for magma mixing. The petrogenesis of the c.v.z. lavas is therefore a complex process in which magmas derived from heterogeneous mantle experience assimilation, fractional crystallization, and magma mixing during uprise through the continental crust.

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A review of Palaeozoic and Mesozoic tetrapods from Greenland

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-2018-66-02 ◽

2018 ◽

Vol 66 ◽

pp. 21-46 ◽

Cited By ~ 2

Author(s):

Marco Marzola ◽

Octávio Mateus ◽

Jesper Milàn ◽

Lars B. Clemmensen

Keyword(s):

Late Jurassic ◽

Early Jurassic ◽

Late Carboniferous ◽

Late Triassic ◽

Late Devonian ◽

Early Triassic ◽

Shallow Marine ◽

East Greenland ◽

Marine Deposits ◽

Theropod Dinosaurs

This article presents a synthesis of Palaeozoic and Mesozoic fossil tetrapods from Greenland, including an updated review of the holotypes and a new photographic record of the main specimens. All fossil tetrapods found are from East Greenland, with at least 30 different known taxa: five stem tetrapods (Acanthostega gunnari, Ichthyostega eigili, I. stensioi, I. watsoni, and Ymeria denticulata) from the Late Devonian of the Aina Dal and Britta Dal Formations; four temnospondyl amphibians (Aquiloniferus kochi, Selenocara groenlandica, Stoschiosaurus nielseni, and Tupilakosaurus heilmani) from the Early Triassic of the Wordie Creek Group; two temnospondyls (Cyclotosaurus naraserluki and Gerrothorax cf. pulcherrimus), one testudinatan (cf. Proganochelys), two stagonolepids (Aetosaurus ferratus and Paratypothorax andressorum), the eudimorphodontid Arcticodactylus, undetermined archosaurs (phytosaurs and both sauropodomorph and theropod dinosaurs), the cynodont Mitredon cromptoni, and three mammals (Haramiyavia clemmenseni, Kuehneotherium, and cf. ?Brachyzostrodon), from the Late Triassic of the Fleming Fjord Formation; one plesiosaur from the Early Jurassic of the Kap Stewart Formation; one plesiosaur and one ichthyosaur from the Late Jurassic of the Kap Leslie Formation, plus a previously unreported Late Jurassic plesiosaur from Kronprins Christian Land. Moreover, fossil tetrapod trackways are known from the Late Carboniferous (morphotype Limnopus) of the Mesters Vig Formation and at least four different morphologies (such as the crocodylomorph Brachychirotherium, the auropodomorph Eosauropus and Evazoum, and the theropodian Grallator) associated to archosaurian trackmakers are known from the Late Triassic of the Fleming Fjord Formation. The presence of rich fossiliferous tetrapod sites in East Greenland is linked to the presence of well-exposed continental and shallow marine deposits with most finds in terrestrial deposits from the Late Devonian and the Late Triassic.

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Supplemental Material: Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

10.1130/gsab.s.17124278.v1 ◽

2021 ◽

Author(s):

Zhenhua Xue ◽

Wei Lin ◽

et al.

Keyword(s):

North China ◽

Stereographic Projection ◽

Magnetic Hysteresis ◽

Central China ◽

Late Triassic ◽

Adjacent Area ◽

Yangtze Block ◽

Data Set ◽

Basic Principles ◽

Magnetic Fabrics

Text: Basic principles of anisotropy of magnetic susceptibility (AMS); Figure S1: Photographs of supplementary shearing indicators of the structural kinematics; Figure S2: Complete magnetic hysteresis data set for specimen selected from 34 sites; Figure S3: Measurements of isothermal remanent magnetization of specimen selected from 34 representative sites of the Bikou Terrane; Figure S4: Thermo-magnetic experiments of specimen selected from 12 representative sites; Figure S5: Mrs/Ms versus Hcr/Hc diagram from the selected specimen of the representative sites to define the size of magnetite; Figure S6: Stereographic projection of the AMS directional fabrics and structural fabrics.

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Mesozoic Coleopteran Faunas from Argentina: Geological Context, Diversity, Taphonomic Observations, and Comparison with Other Fossil Insect Records

Psyche A Journal of Entomology ◽

10.1155/2012/242563 ◽

2012 ◽

Vol 2012 ◽

pp. 1-14 ◽

Cited By ~ 7

Author(s):

María Belén Lara ◽

Oscar Florencio Gallego ◽

Lara Vaz Tassi

Keyword(s):

Late Jurassic ◽

Middle Triassic ◽

Late Triassic ◽

Animal Kingdom ◽

Fossil Insect ◽

San Luis ◽

Fundamental Information ◽

The World ◽

Geological Units ◽

Deseado Massif

The order Coleoptera is the most diversified group of the Class Insecta and is the largest group of the Animal Kingdom. This contribution reviews the Mesozoic insects and especially the coleopteran records from Argentina, based on bibliographical and unpublished materials (86 described species, 526 collected specimens). The material came from different geological units from the late Middle Triassic to the Late Triassic (Bermejo, Cuyo, and Malargüe basins) to the Middle-Late Jurassic and Early Cretaceous (Deseado Massif, Cañadón Asfalto, and San Luís Basin). The coleopteran record is composed of 29 described species with 262 collected specimens (isolated elytra) mainly represented by Triassic species and only four specimens recorded in Jurassic units, all of them currently unpublished. These fossil coleopterans provide fundamental information about the evolution of insects in the Southern Hemisphere and confirm the Triassic Argentinean insect deposits to be among the most important in the world.

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