Integrated geological-geophysical study of the junction zone of Eurasia and Gondwana

Author(s):  
Lev Eppelbaum ◽  
Youri Katz

<p>Tectonically the considered area of junction of four lithospheric plates (Nubian, Arabian, Aegean-Anatolian and Sinai) belongs to the Eastern Mediterranean, with its Cyprus-Levantine marine and Anatolian-Nubian-Arabian continental framing. The anomalousness of the region is manifested in the tectono-structural features of the mantle, lithosphere, hydrosphere and specifics of atmospheric, biospheric processes, and Hominid evolution.</p><p>The study region is distinguished by a complex junction of elements of the continental and oceanic crust. This intricate structure is caused by the simultaneous development of collision processes associated with the latitudinal zone of the Neotethys Ocean closure and manifestation of the initial stages of spreading of the Red Sea – Indian Ocean submeridional rift system. This area is characterized by presence of several geological-geophysical phenomena: (1) anomalous thickening of the mantle lithosphere in the Cyprus-Levantine zone, (2) development of the most ancient oceanic crust block with the Kiama paleomagnetic hyperzone, (3) presence of significant in size and amplitude gravitational and magnetic anomalies and lowest values of thermal flow, (4) presence of mantle diapirs, (5) high seismic activity, (5) development of a counterclockwise circular rotation of the GPS vectors, and (6) the location of the apical part of the oval structure occurring in the Earth's lower mantle. The study area is also distinguished by unique geomorphological and paleogeographic features. At present, the lowest elevations of the earth's surface relief developed here reach –430 m on the Dead Sea coast, and the deepest zones of the Mediterranean Sea almost reach the ultra-abyssal depth of –5267 m in the Calypso depression in the Ionian arc of Greece. In the epoch of the Mediterranean Sea drying out in the end of the Miocene (the Messinian crisis), the earth's surface marks (taking into account the hydro-isostatic effect) could reach 3000-4000 m below the hydrosphere level; this was probably the lowest land hypsometric minimum in the Earth geological history.</p><p>The aforementioned phenomena make it possible to conclude that this region is a giant geodynamic node formed in the northern hemisphere at the intersection of the latitudinal critical parallel (35<sup>о</sup>) in the Eurasia and Gondwana junction zone and the meridional step of the Ural-African geoid anomaly. The combined use of systematic data analysis, geodynamic constructions, structural-tectonic zonation, and cyclic analysis enabled to clarify  the history of geodynamic development and genesis of the tectono-physical formation of individual geological structures, and the region as a whole. </p><p>A special importance was paid to the satellite gravity data analysis with the subsequent modeling and transformation and identification of the heterogeneous structures in the Earth's crust, mantle lithosphere and lower mantle. Paleomagnetic mapping of the region indicates an increase of the frequency and diversity of magmatic complexes from the west to east. Obviously, this manifestation is due to the counterclockwise rotation of the Earth's crust relative to elongated axis of the discovered deep mantle structure (Eppelbaum <em>et al</em>., 2021).</p><p>Eppelbaum, L.V., Ben-Avraham, Z., Katz, Y., Cloetingh, S. and Kaban, M., 2021.<strong> </strong>Giant quasi-ring mantle structure in the African-Arabian junction: Results derived from the geological-geophysical data integration. <em>Geotectonics</em>, <strong>55</strong>, No. 1, 1-28</p>

Author(s):  
V. M. Makeev ◽  
N. V. Makarova ◽  
T. V. Sukhanova

The article deals with the internal deep structure of the earth's crust of the East European platform and the surface of the mantle lithosphere. The presented charts of the three main layers of the earth's crust — the lower, middle and upper and the surface of the mantle lithosphere — for the first time identified deformation by changing the thickness of the layers. Deformations are compared on all layers that allowed to allot the active center, the main (through) and local (developed in separate layers) areas. The boundaries of these regions are active zones of different ranks. The observed end-to-end development of strain from layer to layer or expression of some of them only in separate layers indicates on the sub-horizontal stratification and vertical divisibility of the earth's crust. Deformations of the deep layers are compared with the latest near-surface platform structures. This made it possible to establish a connection of near-surface deformations with deep ones and to consider the latter as the latest. These studies are relevant for solving fundamental problems of the origin of new structures and a number of practical problems.


1969 ◽  
Vol 59 (1) ◽  
pp. 23-42
Author(s):  
Gonzalo Payo

Abstract A large number of observations of phase velocity of Love and Rayleigh waves have been used in order to determine the crust-mantle structure of the Mediterranean Sea. These velocities have been measured by using records from the Standard Stations located in the Mediterranean borders. The empirical dispersion curves have been compared with those of several models computed for this purpose. Travel-time curves of body waves for paths crossing the Mediterranean region, making use of all possible coastal stations and local earthquakes, have been found to substantiate the results from the surface wave dispersion. Also the value of the Bouguer anomaly in different points of the region was considered in the determination of the crustal thickness, as well as some measurements of group velocity from clear observations of higher modes. The crust-mantle structure under the Mediterranean Sea was found to be formed by two clearly distinct zones which correspond roughly to the areas to the west and east of Italy. The western zone, between Italy and Spain, is of oceanic type with a thin crust (about 14 km) and a low-velocity channel in the Upper Mantle. In the eastern zone, south of Greece, the crust (some 23 km thick) shows a great thickness of the uppermost sedimentary layers, which gives rise to very low velocities of short-period surface waves in that region. Love waves with group velocities smaller than those of Rayleigh have been clearly observed in a large number of earthquakes in this region. The surface wave dispersion as well as the travel-time curves of P and S waves of this zone indicate the existence of a low-velocity channel in the Upper Mantle.


Author(s):  
Vladimir Makeev ◽  
Nataliya Makarova

The object of research is the deformation of the deep layers and the Moho surface the East European platform is identified on the basis of structural analysis thickness of the deep layers of the Earth's crust and of the Moho surface. Initial data - geological and geophysical materials of the lithosphere of the East European platform, the thickness of the lower, middle, and upper layers of the Earth's crust, and the newest structures. Research methods are structural-geodynamic and comparative- tectonic, which allow us to assess the spatial and temporal variability of deep and near-surface deformations. Results. Active centers and relatively passive deformations associated are combined into geodynamic regions, the boundaries of which are zones of structural disagreement. Geodynamic regions are divided into main and secondary. The first is expressed by stable and long-term development, the second - is shown in separate layers of the Earth’s crust. It is established that the protrusions of the mantle lithosphere cause a reduction in the thickness of the layers of the Earth's crust and the formation of the newest trough. The sinking of the mantle lithosphere affects the increase in power in the lower and upper layers and the formation of the newest uplifts. The intermediate layer is considered as a compensation layer. Thinning and thick parts of the individual layers lead to the formation of the newest local trough and uplifts. Thus, the conformal and disconform correlation of deformations of deep layers and the newest structures is a characteristic property of the structure of the platform lithosphere. The sources of deep deformations are extra-platform regional areas of recent tectogenesis and intraplatform local active centers - protrusions and trough of the mantle lithosphere, abnormal thickening and thinning of the Earth's crust layers.


1915 ◽  
Vol 79 (2058supp) ◽  
pp. 382-383
Author(s):  
Alphonse Berget

2015 ◽  
Vol 116 (1) ◽  
pp. 69-74 ◽  
Author(s):  
L Pérez ◽  
ML Abarca ◽  
F Latif-Eugenín ◽  
R Beaz-Hidalgo ◽  
MJ Figueras ◽  
...  

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