Showing papers on "Continental margin published in 2021"
TL;DR: In this paper, a review of the main Eoarchean supracrustal belts of the world, constrained by relevant geochemical/isotopic data, is presented evidence that suggests that from at least ca. 4.0 -4.2 -Ga to 2.7 -2.5 -Ga Earth produced considerable juvenile mafic crust and consequent island arcs by Accretionary Cycle Plate Tectonics.
113 citations
TL;DR: The turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase, and it is found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene−Oligocene transition about 30 million years before present.
Abstract: Living turtles are characterized by extraordinarily low species diversity given their age. The clade’s extensive fossil record indicates that climate and biogeography may have played important roles in determining their diversity. We investigated this hypothesis by collecting a molecular dataset for 591 individual turtles that, together, represent 80% of all turtle species, including representatives of all families and 98% of genera, and used it to jointly estimate phylogeny and divergence times. We found that the turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase. We also found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene−Oligocene transition about 30 million years before present. In apparent contrast, the fossil record from this time period contains evidence for a major, but regional, extinction event. These seemingly discordant findings appear to be driven by a common global process: global cooling and drying at the time of the Eocene−Oligocene transition. This climatic shift led to aridification that drove extinctions in important fossil-bearing areas, while simultaneously exposing new continental margin habitat that subsequently allowed for a burst of speciation associated with these newly exploitable ecological opportunities.
75 citations
TL;DR: Yanshanian metallogeny of eastern Asia was dominantly controlled by oblique subduction and rollback of the Izanagi plate, and also, more locally in the north, by closure of the Mudanjiang Ocean basin and accretion of the Bureya-Jiamusi-Khanka block and the Sikhote-Alin terranes as discussed by the authors.
63 citations
TL;DR: In this paper, the authors used a regional tectonic reconstruction of the Western Mediterranean-Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modeling of the rifting phase.
Abstract: . Assessing the size of a former ocean of which only remnants are found in mountain belts is challenging but crucial to understanding subduction and exhumation processes. Here we present new constraints on the opening and width of the Piemont–Liguria (PL) Ocean, known as the Alpine Tethys together with the Valais Basin. We use a regional tectonic reconstruction of the Western Mediterranean–Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modeling of the rifting phase to test our kinematic reconstructions for geodynamic consistency. Our model fits well with independent datasets (i.e., ages of syn-rift sediments, rift-related fault activity, and mafic rocks) and shows that, between Europe and northern Adria, the PL Basin opened in four stages: (1) rifting of the proximal continental margin in the Early Jurassic (200–180 Ma), (2) hyper-extension of the distal margin in the Early to Middle Jurassic (180–165 Ma), (3) ocean–continent transition (OCT) formation with mantle exhumation and MORB-type magmatism in the Middle–Late Jurassic (165–154 Ma), and (4) breakup and mature oceanic spreading mostly in the Late Jurassic (154–145 Ma). Spreading was slow to ultra-slow (max. 22 mm yr−1 , full rate) and decreased to ∼5 mm yr−1 after 145 Ma while completely ceasing at about 130 Ma due to the motion of Iberia relative to Europe during the opening of the North Atlantic. The final width of the PL mature (“true”) oceanic crust reached a maximum of 250 km along a NW–SE transect between Europe and northwestern Adria. Plate convergence along that same transect has reached 680 km since 84 Ma (420 km between 84–35 Ma, 260 km between 35–0 Ma), which greatly exceeds the width of the ocean. We suggest that at least 63 % of the subducted and accreted material was highly thinned continental lithosphere and most of the Alpine Tethys units exhumed today derived from OCT zones. Our work highlights the significant proportion of distal rifted continental margins involved in subduction and exhumation processes and provides quantitative estimates for future geodynamic modeling and a better understanding of the Alpine Orogeny.
58 citations
TL;DR: In this paper, the authors assess the accuracy of a set of Phanerozoic digital paleogeographic maps by testing the proposed distribution of flooded shallow seas and land using fossil occurrence data from the Paleobiology Database.
42 citations
TL;DR: The Alps are among the best subduction archives in the world, with abundant blueschists and eclogites preserving fragments of mantle, gabbros, thinned continental margin and pelagic sediments partly within their precollisional architecture as discussed by the authors.
41 citations
TL;DR: In this paper, the authors describe how an active continental margin extensional setting can also define an important tectonic environment for the development of a world-class regional metallogenic province subsequent to subduction and compressional stresses.
37 citations
TL;DR: In this article, the authors performed a comprehensive analysis of seismic profiles and fault architecture data with a view to understand the Cenozoic tectonic evolution of the northern margin of the South China Sea (SCS).
31 citations
TL;DR: In this paper, a series of paleogeographic maps, developed in response to temporally and spatially changing influences of climate, eustasy, and a continent-wide late Paleozoic orogenic system, are presented.
26 citations
TL;DR: In particular, the impact of hydrodynamic processes on the age, abundance, and stable isotopic composition of sedimentary organic carbon (OC) burial is poorly constrained as discussed by the authors.
25 citations
TL;DR: In this paper, regional triplication waveforms of five intermediate-depth events are modeled to simultaneously obtain the compressional (P) and shear (SH) wave velocity structure under the northwestern Pacific subduction zone.
TL;DR: In this paper, the authors review the current state of this field and discuss types of oceanic plateaus subduction by combining and comparing natural observations and numerical models, and identify three modes of Oceanic Plateau subduction in both nature and models.
TL;DR: In this article, the authors present novel findings on the Pliocene and Quaternary evolution of the Gela Basin (Strait of Sicily, Mediterranean Sea), an area recording the interaction between tectonics, climate change at Milankovitch and sub-Milankovitches timescales, and dynamic water masses exchange between the eastern and western Mediterranean Sea.
TL;DR: A bathymetric map of the South African continental shelf derived from digital single-beam echo-sounding data collected by the Department of Agriculture, Forestry and Fisheries (DAFF) that is at a significantly higher resolution than was previously available as presented by Dingle et al..
Abstract: Detailed knowledge of shelf bathymetry is essential for understanding the long-term geological evolution of continental margins, the extent of the coastal plain as the shoreline moved in response to Pleistocene sea-level fluctuations, and for ecosystems management, resource exploration, and navigation. Although some areas have been mapped in detail, most South African shelf bathymetry is poorly resolved. This paper presents a bathymetric map of the South African continental shelf derived from digital single-beam echo-sounding data collected by the Department of Agriculture, Forestry and Fisheries (DAFF) that is at a significantly higher resolution than was previously available as presented by Dingle et al. (Annals of the South African Museum 98:1–27, 1987). The bathymetric dataset consists of approximately 7 million data sonar points collected by the Fisheries Division of DAFF over the last two decades, covering the entire South African continental shelf area of 541,000 km2 between the Orange River mouth on the West Coast and Kosi Bay on the East Coast. The new map not only resolves known shelf bathymetric features in greater detail but also reveals new features. The origin of some bathymetric features remains unknown, but many appear to relate to bedrock geology, sediment deposition (river drainage systems and ocean currents), and sea-level fluctuations.
TL;DR: Wang et al. as discussed by the authors proposed a trans-crustal magma system model for the Cretaceous volcanic-plutonic rocks in SE China, which showed that significant fractionation combining distinct contribution of crustal materials can interpret the dominant felsic component feature.
TL;DR: In this article, in situ zircon U-Pb ages and geochemistry were conducted on both granitic and metasedimentary borehole samples from immediately below the Cenozoic sedimentary cover of the northern South China Sea basin.
TL;DR: In this article, the main ideas and models for the subduction initiation at passive margin are classified into two categories, i.e. driven by either local forces or external forces, which are feasible to drive SI for young oceanic basins with thin and weak lithosphere on the present Earth.
TL;DR: In this article, three examples of stacked vent complexes are presented, revealing large eruptions of hydrothermal fluids vertically through the same conduit, from sills to the palaeo-sea floor.
Abstract: Conventional three‐dimensional (3D) seismic data reveal abundant igneous activity on the Modgunn Arch, mid‐Norwegian margin. Magmatic sills and associated hydrothermal vent complexes located at various depths prove the repeated utilisation of Paleocene‐Eocene magmatic conduits. In total, 125 sills and 85 hydrothermal vent complexes were identified and mapped, with vent complexes ranging in diameter from 300 to 3,100 m and sills from 0.5 to 50 km. Three examples of stacked vent complexes are presented, revealing large eruptions of hydrothermal fluids vertically through the same conduit, from sills to the palaeo‐sea floor. The vent complexes are found throughout Paleocene strata (66–56 Ma), whilst at least ten (10) vents were active during the Eocene. This study emphasises the importance of characterising ancient magmatic structures, as hydrothermal conduits and vent structures were, and may still be, reutilised as preferential fluid flow pathways to shallower strata. A minimum of four phases of hydrothermal vent complex formation are inferred. Cretaceous faults are both bypassed and used for magma and fluid flow. The reutilisation of magmatic structures here described may bring to light previously overlooked plays and renew interest in exploring magma‐rich continental margins.
TL;DR: In this paper, the LS17-2 and LW3-1 gas fields, the respective largest gas field in the deepwater areas of the QDN and PRM basins, were investigated.
TL;DR: In this paper, the Hillary Canyon was analyzed to understand how dense shelf water and other continental slope processes influence submarine canyon morphology by analysing newly collected geophysical and oceanographic data from a region of significant and prolonged dense shelf waters export, the Hillary canyon in the Ross Sea.
TL;DR: In this article, the authors proposed that the Avalonian basement was amalgamated after inferred late Ediacaran ridge-trench collision that initiated the northerly-southernly trending Avalonian transform fault (Atf, new).
TL;DR: In this article, the authors present a study based on new and compiled geochronological and geochemical data to assess the tectonomagmatic evolution of Mexico from the Late Cretaceous and Eocene (~90-40 Ma).
TL;DR: The early Aptian Oceanic Anoxic Event 1a (OAE 1a) was associated with marked changes in palaeoclimate linked to a perturbation of the global carbon cycle as discussed by the authors.
TL;DR: In this paper, the morphosedimentary characteristics of a large CDS were analyzed together with the current dynamics along the northern Argentine continental margin, where the authors used multibeam bathymetry, seismo-acoustic data, sediment samples, vessel-mounted Acoustic Doppler Current Profiler (VM-ADCP) data and numerical modelling of ocean currents.
TL;DR: In this article, a detailed documentation of the PETM in the Xigaze forearc basin located along the northern active continental margin of the eastern Tethys Ocean is presented, and illustrates the associated environmental and hydrological changes.
TL;DR: In this article, the impact of deformation partitioning on the structure and evolution of orogens by examining the Taiwan mountain belt as a case study is discussed, and the role played by decollements or weak zones in crustal deformation is discussed.
Abstract: Many orogens on the planet result from plate convergence involving subduction of a continental margin. The lithosphere is strongly deformed during mountain building involving subduction of a plate composed generally of accreted continental margin units and some fragments of downgoing oceanic crust and mantle. A complex deformation involving strong partitioning of deformation modes and kinematics produces crustal shortening, accompanied by crustal thickening. Partitioning depends on three main factors: (1) rheologic layering of the lithosphere; (2) interaction between tectonics and surface processes; (3) subduction kinematics and 3D geometry of continental margins (oblique convergence, shape of indenters). Here we present an original view and discussion on the impact of deformation partitioning on the structure and evolution of orogens by examining the Taiwan mountain belt as a case study. Major unsolved questions are addressed through geological observations from the Taiwan orogen and insights from analogue models integrating surface processes. Some of these questions include: What is the role played by decollements or weak zones in crustal deformation and what is the impact of structural heterogeneities inherited from the early extensional history of a rifted passive continental margin? What is the relationship between deep underplating, induced uplift and flow of crustal material during erosion (finite strain evolution during wedge growth)? Are syn-convergent normal faults an effect of deformation partitioning and erosion? What is the role of strain partitioning on the location of major seismogenic faults in active mountain belts? What can be learned about the long-term and the present-day evolution of Taiwan?
TL;DR: The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene as mentioned in this paper, and the dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion.
Abstract: The Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.