scholarly journals DEEP CRUSTAL STRUCTURE IN NORTHEASTERN EURASIA AND ITS CONTINENTAL MARGINS

2021 ◽  
Vol 12 (2) ◽  
pp. 199-224
Author(s):  
S. N. Kashubin ◽  
O. V. Petrov ◽  
S. P. Shokalsky ◽  
E. D. Milshtein ◽  
E. A. Androsov ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Vertical Section ◽  
Sedimentary Cover ◽  
Passive Margin ◽  
The Arctic ◽  
Crust And Upper Mantle ◽  
Consolidated Crust ◽  
The Pacific ◽  
Deep Crustal Structure ◽  
Moho Depths

The paper reports on the deep geophysical studies performed by the Geological Survey of Russia (VSEGEI) under the international project – Deep Processes and Metallogeny of Northern, Central and Eastern Asia. A model of the deep crustal structure is represented by a set of crustal thickness maps and a 5400-km long geotransect across the major tectonic areas of Northeastern Eurasia. An area of 50000000 km2 is digitally mapped in the uniform projection. The maps show the Moho depths, thicknesses of the main crustal units (i.e. the sedimentary cover and the consolidated crust), anomalous gravity and magnetic fields (in a schematic zoning map of the study area), and types of the crust. The geotransect gives the vertical section of the crust and upper mantle at the passive margin of the Eurasian continent (including submarine uplifts and shelf areas of the Arctic Ocean) and the active eastern continental margin, as well as an area of the Pacific plate.

Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment) – II. Sardinia’s margin

2015 ◽  
Vol 186 (4-5) ◽  
pp. 331-351 ◽  
Author(s):  
Alexandra Afilhado ◽  
Maryline Moulin ◽  
Daniel Aslanian ◽  
Philippe Schnürle ◽  
Frauke Klingelhoefer ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Passive Margin ◽  
Data Sets ◽  
Wide Angle ◽  
Seismic Velocities ◽  
The West ◽  
Reflection Seismic ◽  
Gulf Of Lion ◽  
Deep Crustal Structure ◽  
Domain Iii

Abstract Geophysical data acquired on the conjugate margins system of the Gulf of Lion and West Sardinia (GLWS) is unique in its ability to address fundamental questions about rifting (i.e. crustal thinning, the nature of the continent-ocean transition zone, the style of rifting and subsequent evolution, and the connection between deep and surface processes). While the Gulf of Lion (GoL) was the site of several deep seismic experiments, which occurred before the SARDINIA Experiment (ESP and ECORS Experiments in 1981 and 1988 respectively), the crustal structure of the West Sardinia margin remains unknown. This paper describes the first modeling of wide-angle and near-vertical reflection multi-channel seismic (MCS) profiles crossing the West Sardinia margin, in the Mediterranean Sea. The profiles were acquired, together with the exact conjugate of the profiles crossing the GoL, during the SARDINIA experiment in December 2006 with the French R/V L’Atalante. Forward wide-angle modeling of both data sets (wide-angle and multi-channel seismic) confirms that the margin is characterized by three distinct domains following the onshore unthinned, 26 km-thick continental crust : Domain V, where the crust thins from ~26 to 6 km in a width of about 75 km; Domain IV where the basement is characterized by high velocity gradients and lower crustal seismic velocities from 6.8 to 7.25 km/s, which are atypical for either crustal or upper mantle material, and Domain III composed of “atypical” oceanic crust. The structure observed on the West Sardinian margin presents a distribution of seismic velocities that is symmetrical with those observed on the Gulf of Lion’s side, except for the dimension of each domain and with respect to the initiation of seafloor spreading. This result does not support the hypothesis of simple shear mechanism operating along a lithospheric detachment during the formation of the Liguro-Provencal basin.

New CGMW Tectonic Map of the Arctic

2020 ◽  
Author(s):  
Oleg Petrov ◽  
Manuel Pubellier ◽  
Andrey Morozov ◽  
Sergey Kashubin ◽  
Sergey Shokalsky ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Sedimentary Cover ◽  
Three Dimensional ◽  
Arctic Region ◽  
Geological Mapping ◽  
The Arctic ◽  
Northern Eurasia ◽  
Consolidated Crust ◽  
Circumpolar Arctic ◽  
Cover Thickness

<p>In 2019, the compilation of the new Tectonic Map of the Arctic (Tectonic Map of the Arctic, 2019: eds. O. Petrov, M. Pubellier) was completed. The map was compiled under the international project Atlas of Geological Maps of the Circumpolar Arctic, 1:5M with the participation of representatives of all Arctic states under the auspices of the Commission for the Geological Map of the World at UNESCO. The new 1:5M Tectonic map of the Arctic is a GIS project, which provides a transition to three-dimensional geological mapping of the Arctic. The project includes the crustal and sedimentary cover thickness maps, the crustal types map, the tectonic zonality map of the basement, schematic  map of key igneous provinces of the Circum-Arctic region and the geological transect compiled taking into account the latest scientific geological and geophysical data accumulated in recent decades as a result of high-latitude expeditions and scientific programs to substantiate the extended continental shelf in the Arctic. The new Tectonic map of the Arctic proved the continental nature of the Central Arctic Uplifts as a natural geological extension of Eurasia. Close structural relationships of deep-water parts of the Central Arctic and the shallow continental shelf of Northern Eurasia are substantiated by geological and geophysical characteristics of the consolidated crust, the upper mantle and sedimentary cover, as well as the common parameters of the magnetic and gravitational potential fields.</p>

scholarly journals Deep structure and metallogeny of the earth's crust

1989 ◽  
Vol 20 (2) ◽  
pp. 37
Author(s):  
V.A. Erkhow
Keyword(s):  
Crustal Structure ◽  
Upper Mantle ◽  
Deep Structure ◽  
Earth’S Crust ◽  
Magnetic Data ◽  
Crust And Upper Mantle ◽  
Geophysical Field ◽  
Deep Crust ◽  
Deep Crustal Structure ◽  
Earth's Crust

Considerable experience with integrated geological and geophysical studies has enabled definition of deep crustal structures and, within limits, composition and processes within the deep crust, and to determine their association with metallogeny in the USSR.By means of seismic experiments, stratification of the Earth's crust and the upper mantle to a depth of about 100 km has been revealed. Numerous heat flow data have been compiled. Magneto-telluric soundings made it possible to determine the position of conductive strata in the crust and upper mantle for a number of areas. Gravity surveys coupled with the results of seismic profiling enabled the finding of a number of empirical laws that are useful for investigation into the deep crust. Magnetic data analysis has enabled evaluation of the magnetic layering of the deep crust. Kimberlite and ore provinces can be considered examples of these concepts.For more detailed studies of deep crustal structure the territory of the USSR is the subject of a system of regional investigation of the deep crust and upper mantle. This system is based principally upon a network of interconnected regional profiles (geotraverses) tied to deep and superdeep boreholes. The system includes predicted geophysical observations to control investigation of the geophysical field data. The geotraverse network is the basis for detailed studies within the bounds of petroleum and ore provinces.The most accurate data obtained allows the formation of a crustal model and reveals empirical relationships with metallogeny.Based on the deep crustal structure data a regional oregenesis prediction map has been made. The endogenous mineralization prediction was based on special features of the upper layering of the crust and on data relating to deep crustal permeability zones.

scholarly journals Retrieval of Summer Sea Ice Concentration in the Pacific Arctic Ocean from AMSR2 Observations and Numerical Weather Data Using Random Forest Regression

2021 ◽  
Vol 13 (12) ◽  
pp. 2283
Author(s):  
Hyangsun Han ◽  
Sungjae Lee ◽  
Hyun-Cheol Kim ◽  
Miae Kim
Keyword(s):  
Random Forest ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Open Water ◽  
The Arctic ◽  
Atmospheric Effects ◽  
Sea Ice Concentration ◽  
Air Temperatures ◽  
The Pacific ◽  
Ice Concentration

The Arctic sea ice concentration (SIC) in summer is a key indicator of global climate change and important information for the development of a more economically valuable Northern Sea Route. Passive microwave (PM) sensors have provided information on the SIC since the 1970s by observing the brightness temperature (TB) of sea ice and open water. However, the SIC in the Arctic estimated by operational algorithms for PM observations is very inaccurate in summer because the TB values of sea ice and open water become similar due to atmospheric effects. In this study, we developed a summer SIC retrieval model for the Pacific Arctic Ocean using Advanced Microwave Scanning Radiometer 2 (AMSR2) observations and European Reanalysis Agency-5 (ERA-5) reanalysis fields based on Random Forest (RF) regression. SIC values computed from the ice/water maps generated from the Korean Multi-purpose Satellite-5 synthetic aperture radar images from July to September in 2015–2017 were used as a reference dataset. A total of 24 features including the TB values of AMSR2 channels, the ratios of TB values (the polarization ratio and the spectral gradient ratio (GR)), total columnar water vapor (TCWV), wind speed, air temperature at 2 m and 925 hPa, and the 30-day average of the air temperatures from the ERA-5 were used as the input variables for the RF model. The RF model showed greatly superior performance in retrieving summer SIC values in the Pacific Arctic Ocean to the Bootstrap (BT) and Arctic Radiation and Turbulence Interaction STudy (ARTIST) Sea Ice (ASI) algorithms under various atmospheric conditions. The root mean square error (RMSE) of the RF SIC values was 7.89% compared to the reference SIC values. The BT and ASI SIC values had three times greater values of RMSE (20.19% and 21.39%, respectively) than the RF SIC values. The air temperatures at 2 m and 925 hPa and their 30-day averages, which indicate the ice surface melting conditions, as well as the GR using the vertically polarized channels at 23 GHz and 18 GHz (GR(23V18V)), TCWV, and GR(36V18V), which accounts for atmospheric water content, were identified as the variables that contributed greatly to the RF model. These important variables allowed the RF model to retrieve unbiased and accurate SIC values by taking into account the changes in TB values of sea ice and open water caused by atmospheric effects.

scholarly journals A warm jet in a cold ocean

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jennifer A. MacKinnon ◽  
Harper L. Simmons ◽  
John Hargrove ◽  
Jim Thomson ◽  
Thomas Peacock ◽  
...  
Keyword(s):  
The Arctic ◽  
Bering Strait ◽  
Near Surface ◽  
Ice Melt ◽  
Beaufort Gyre ◽  
The Pacific ◽  
Climate Simulations ◽  
Initial Evolution ◽  
Forecast Models

AbstractUnprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.

scholarly journals Deep Crustal Structure of the Capricorn Orogen from Gravity and Seismic Data

2015 ◽  
Vol 2015 (1) ◽  
pp. 1-3
Author(s):  
Abdulrhman H. Alghamdi ◽  
Alan R.A. Aitken ◽  
Michael C. Dentith
Keyword(s):  
Crustal Structure ◽  
Seismic Data ◽  
Deep Crustal Structure

scholarly journals A subduction influence on ocean ridge basalts outside the Pacific subduction shield

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Y. Yang ◽  
C. H. Langmuir ◽  
Y. Cai ◽  
P. Michael ◽  
S. L. Goldstein ◽  
...  
Keyword(s):  
Upper Mantle ◽  
The Arctic ◽  
Mantle Flow ◽  
Mantle Heterogeneity ◽  
Gakkel Ridge ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
The Pacific Ocean ◽  
Back Arc ◽  
Ocean Ridge

AbstractThe plate tectonic cycle produces chemically distinct mid-ocean ridge basalts and arc volcanics, with the latter enriched in elements such as Ba, Rb, Th, Sr and Pb and depleted in Nb owing to the water-rich flux from the subducted slab. Basalts from back-arc basins, with intermediate compositions, show that such a slab flux can be transported behind the volcanic front of the arc and incorporated into mantle flow. Hence it is puzzling why melts of subduction-modified mantle have rarely been recognized in mid-ocean ridge basalts. Here we report the first mid-ocean ridge basalt samples with distinct arc signatures, akin to back-arc basin basalts, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence in this region. This influence can also be identified in Atlantic and Indian mid-ocean ridge basalts but is nearly absent in Pacific mid-ocean ridge basalts. Such a hemispheric-scale upper mantle heterogeneity reflects subduction modification of the asthenospheric mantle which is incorporated into mantle flow, and whose geographical distribution is controlled dominantly by a “subduction shield” that has surrounded the Pacific Ocean for 180 Myr. Simple modeling suggests that a slab flux equivalent to ~13% of the output at arcs is incorporated into the convecting upper mantle.

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