The transition of the East European cratonic lithosphere to that of the Palaeozoic collage of the Trans-European Suture Zone as depicted on the TTZ-South deep seismic profile (SE Poland to NW Ukraine)

2020 ◽  
Author(s):  
Tomasz Janik ◽  
Vitaly Starostenko ◽  
Paweł Aleksandrowski ◽  
Tamara Yegorova ◽  
Wojciech Czuba ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Lower Crust ◽  
Seismic Velocity ◽  
Sedimentary Cover ◽  
Suture Zone ◽  
Crystalline Basement ◽  
Moho Depth ◽  
Crustal Layer ◽  
Velocity Inversion ◽  
East European

<p>Crustal and uppermost mantle structure along the Teisseyre-Tornquist Zone (TTZ)  was explored along the ~550 km long, NW-SE-trending TTZ-South profile, using seismic wide-angle reflection/refraction (WARR) method. The profile line was intended to follow the border between the East European Craton (EEC) and the so called Palaeozoic Platform (PP) of north-central Europe, believed to contain a number of crustal blocks that were accreted to the craton during pre-late Carboniferous times, defining the Trans-European Suture Zone (TESZ).</p><p>The seismic velocity model of the TTZ-South profile shows lateral variations in crustal structure. Its Ukrainian segment crosses the interior of the Sarmatian segment of the EEC, where the crystalline basement gradually dips from ~2 km depth in the SE to ~12 km at the Ukrainian-Polish border. This part of the model shows a four-layered crustal structure, with an up to 15 km-thick sedimentary cover, an underlying crystalline upper crust, a 10-15 km-thick middle crust and a ~15 km thick lower crust. In Poland, the profile passes along the TESZ/EEC transition zone of complex crustal structure. The crystalline basement, whose top occurs at depths of 10-17 km, separates the sedimentary cover from the ~10 km thick mid-crustal layer (Vp=6.5-6.6 km/s), which, in turn, overlies a block of 10-15 km thickness with upper crustal velocities (Vp~6.2 km/s). The latter is underlain by a ~10-15 km-thick lower crust. Along most of the model one can see conspicuous velocity inversion zones occuring at various depths. At intersections of the TTZ-South profile with some previous deep seismic profiles (e.g. CEL02, CEL05, CEL14, PANCAKE) such inversions document complex wedging relationships between the EEC and PP crustal units. These may have resulted from tectonic compression and thick-skinned thrusting due to either Neoproterozoic EEC collision with accreting terranes or intense Variscan orogenic events. Five high velocity bodies (HVB; V<sub>p</sub> = 6.85-7.2 km/s) were detected in the middle and lower crust at 15-37 km depth. The Moho depth varies substantially along the profile. It is at ~42 km depth in the NW and deepens SE-ward to ~50 km at ~685 km. Subsequently, it rises abruptly to ~43 km at the border of the Sarmatian segment of the EEC and sinks again to ~50 km beneath the Lviv Paleozoic trough at ~785 km. From this point until the SE end of the profile, the Moho gently shallows, up to a depth of ~37 km, including a step-like jump of 2 km at ~875 km. Such abrupt Moho steps may be related to crust-scale strike-slip faults. Along the whole profile, sub-Moho velocities are ~8.05-8.1 km/s, and at depths of 57-63 km Vp values reach 8.2-8.25 km/s. Four reflectors/refractors were modelled in the upper mantle at ~57-65 km and ~80 km depths.</p>

Crustal structure at the Trans-European Suture Zone in northwest Poland based on gravity data

1997 ◽  
Vol 134 (5) ◽  
pp. 661-667 ◽  
Author(s):  
C. KRÓLIKOWSKI ◽  
Z. PETECKI
Keyword(s):  
Crustal Structure ◽  
Gravity Data ◽  
Sedimentary Cover ◽  
Bouguer Anomaly ◽  
Three Dimensional ◽  
Suture Zone ◽  
Long Wavelength ◽  
Dimensional Gravity ◽  
Anomaly Map ◽  
Northwestern Poland

A new gravity model of the crustal structure of the Trans-European Suture Zone in the northwestern Poland has been constructed. The Bouguer anomaly map, obtained after stripping off the three-dimensional gravity effect of the sedimentary cover down to the Zechstein formations, is characterized by a 50 mGal gravity anomaly. We have assumed that the short-wavelength components derive from upper crustal intrusions and the long-wavelength components reflect crustal thickness and lateral heterogeneity which are strongly supported by the new seismic data along the LT-7 geotraverse. Quantitative modelling of gravity data along three profiles crossing the area indicate the presence of anomalous masses within the Lower Palaeozoic sequence, mainly along the Teisseyre-Tornquist Zone. Two of the profiles crossing the long-wavelength ‘stripped’ gravity high suggest the existence of a zone of 35 km crust above a dense upper mantle along the Teisseyre-Tornquist Zone. The extent of the zone can be determined based on the Bouguer anomalies interpretation.

Seismic velocity structure of the Queen Charlotte Basin beneath Hecate Strait

1993 ◽  
Vol 30 (4) ◽  
pp. 787-805 ◽  
Author(s):  
G. D. Spence ◽  
I. Asudeh
Keyword(s):  
Lower Crust ◽  
Constant Velocity ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Moho Depth ◽  
Moderate Increase ◽  
Central Basin ◽  
Velocity Models ◽  
Brittle Ductile Transition ◽  
Numerical Predictions

Seismic refraction data across Hecate Strait in the northern Queen Charlotte Basin were collected in a coincident reflection and refraction survey. Crustal velocity models provide a framework to help understand the formation of the sedimentary basin and the processes occurring near the Queen Charlotte Fault, a major ocean–continent transform fault. Beneath the sediments, which have a maximum thickness of 6 km, a velocity gradient extends from about 5 to 8 km depth, within which velocities increase typically from 6.3 to 6.4 km∙s−1. A thick constant-velocity region was found down to a depth varying from 14 to 22 km, with the smallest depths located beneath the central basin. The base of the constant-velocity layer was marked by a distinct mid-crustal interface, across which velocities increased from 6.4–6.5 km∙s−1 to approximately 6.8–6.9 km∙s−1. Moho was interpreted to be at a near-uniform depth of 26–28 km beneath Hecate Strait and the eastern Queen Charlotte Islands. The associated variation in crustal thickness beneath the basin implies crustal thinning, perhaps caused by extension, of 30% or more.The mid-crustal interface may mark the change to a more mafic and perhaps ductile lower crust. The interface appears to be about 1–4 km deeper than the brittle–ductile transition, as indicated by the estimated depth to the 450 °C isotherm and by the moderate increase in reflectivity on the seismic reflection sections. Ductile flow may also occur in the lower crust near the Queen Charlotte Fault, where the relative motion of the oceanic plate induces lithospheric flow and thinning beneath both the ocean and the continent. The observed decrease in Moho depth from 28 to 21 km near the fault is consistent with recent (1989) numerical predictions of I. Reid for lithospheric flow near ocean–continent transforms.

scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2011 ◽  
Vol 2(11)2011 (2(11)) ◽  
pp. 89-91
Author(s):  
G. Ivanchenko ◽  
◽  
E. M. Horbunova ◽  
Keyword(s):  
East European Platform ◽  
Satellite Images ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Geophysical Data ◽  
East European ◽  
Neotectonic Activity ◽  
Automated Interpretation ◽  
Basement Structures ◽  
The Relationship

The relationship between the structures of the crystalline basement, structures of the sedimentary cover and relief of the day surface was traced on the basis of the geological and geophysical data and the results of visual and automated interpretation of the satellite images of the central part of East European Platform. Completed research allowed to determine the extent of the neotectonic activity of morphostructures influencing at the formation of the geophysical fields.

Crustal structure of the Nova Scotian margin in the Laurentian Channel region

1987 ◽  
Vol 24 (9) ◽  
pp. 1859-1868 ◽  
Author(s):  
I. Reid
Keyword(s):  
Crustal Structure ◽  
Seismic Velocity ◽  
Structural Information ◽  
Seismic Refraction ◽  
Ocean Bottom ◽  
Eastern Canada ◽  
Crustal Layer ◽  
Air Gun ◽  
Lower Crustal

A seismic-refraction study on the outer Scotian Shelf of eastern Canada, carried out using large air-gun sources and ocean bottom seismograph receivers, has provided structural information on the entire crustal column. A thick (about 13 km) sedimentary sequence is characterized by significant lateral variation in this area, and a marked increase in seismic velocity around 8 km depth may delineate the synrift–postrift transition. Beneath the sediments is highly attenuated continental crust, about 11 km thick, with some evidence for a lower crustal layer of velocity around 7 km/s, which may be partly due to under-plating during rifting. Determination of the complete crustal structure, including the tentative delineation of the rift–drift transition, in a region of large crustal extension provides a useful test for models of continental rifting, and a simple uniform extension–subsidence model is found to produce an adequate fit to the interpreted structure.

Crustal structure across the Nain – Makkovik boundary on the continental shelf off Labrador from seismic refraction data

1996 ◽  
Vol 33 (3) ◽  
pp. 460-471 ◽  
Author(s):  
Ian Reid
Keyword(s):  
Continental Shelf ◽  
Wave Velocity ◽  
Crustal Structure ◽  
Lower Crust ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
P Wave ◽  
Air Gun ◽  
P Wave Velocity

A detailed seismic refraction profile was shot along the continental shelf off Labrador, across the boundary between the Archean Nain Province to the north and the Proterozoic Makkovik orogenic zone to the south. A large air-gun source was used, with five ocean-bottom seismometers as receivers. The data were analysed by forward modelling of traveltimes and amplitudes and provided a well-determined seismic velocity structure of the crust along the profile. Within the Nain province, thin postrift sediments are underlain by crust with a P-wave velocity of 6.1 km/s, which increases with depth and reaches 6.6 km/s at about 8 km. Moho is at around 28 km, and there is no evidence for a high-velocity (>7 km/s) lower crust. The P- and S-wave velocity structure is consistent with a gneissic composition for the Archean upper crust, and with granulites becoming gradually more mafic with depth for the intermediate and lower crust. In the Makkovik zone, the sediments are thicker, and a basement layer of P-wave velocity 5.5–5.7 km/s is present, probably due to reworking of the crust and the presence of Early Proterozoic volcanics and metasediments. Upper crustal velocities are lower than in the Nain Province. The crustal thickness, at 23 km, is less, possibly due in part to greater crustal stretching during the Mesozoic rifting of the Labrador Sea. The crustal structure across the Nain–Makkovik boundary is similar to that across the corresponding Archean–Ketilidian boundary off southwest Greenland.

scholarly journals Crustal structure of the Volgo-Uralian subcraton revealed by inverse and forward gravity modeling

2021 ◽  
Author(s):  
Igor Ognev ◽  
Jörg Ebbing ◽  
Peter Haas
Keyword(s):  
Crustal Structure ◽  
Seismic Data ◽  
Lower Crust ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Gravity Modeling ◽  
Gravity Inversion ◽  
Ural Mountains ◽  
Satellite Gravity ◽  
Crustal Model

Abstract. Volgo-Uralia is a Neoarchean easternmost part of the East European craton. Recent seismic studies of the Volgo-Uralian region provided new insights into the crustal structure of this area. In this study, we combine satellite gravity and seismic data in a common workflow to perform a complex study of Volgo-Uralian crustal structure which is useful for further basin analysis of the area. In this light, a new crustal model of the Volgo-Uralian subcraton is presented from a step-wise approach: (1) inverse gravity modeling followed by (2) 3D forward gravity modeling. First, inversion of satellite gravity gradient data was applied to determine the Moho depth for the area. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region, and the model is constrained by the available active seismic data. The Moho discontinuity obtained from the gravity inversion was consequently modified and complemented in order to define a complete 3D crustal model by adding information on the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling where both seismic and gravity constraints were respected. The obtained model shows crustal thickness variations from 32 to more than 55 km in certain areas. The thinnest crust with a thickness below 40 km is found beneath the Pericaspian basin, which is covered by a thick sedimentary layer. The thickest crust is located underneath the Ural Mountains as well as in the center of the Volga-Uralian subcraton. In both areas the crustal thickness exceeds 50 km. At the same time, initial forward gravity modeling has shown a gravity misfit of ca. 95 mGal between the measured Bouguer gravity anomaly and the forward calculated gravity field in the central area of the Volga-Uralian subcraton. This misfit was interpreted and modeled as a high-density lower crust which possibly represents underplated material. Our preferred crustal model of the Volga-Uralian subcraton respects the gravity and seismic constraints and reflects the main geological features of the region with Moho thickening in the cratons and under the Ural Mountains and thinning along the Paleoproterozoic rifts, Pericaspian sedimentary basin, and Pre-Urals foredeep.

Transition from oceanic to continental crustal structure: seismic and gravity models at the Queen Charlotte transform margin

1995 ◽  
Vol 32 (6) ◽  
pp. 699-717 ◽  
Author(s):  
G. D. Spence ◽  
D. T. Long
Keyword(s):  
Continental Crust ◽  
Triple Junction ◽  
Lower Crust ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Gravity Models ◽  
Moho Depth ◽  
Horizontal Distance ◽  
Velocity Models

Seismic refraction data have been interpreted along a line crossing the Queen Charlotte transform, just north of the triple junction where the Explorer Ridge intersects the continental margin. These data, observed at three onshore sites, help to define the structure of the continental crust beneath the Queen Charlotte sedimentary basin. Sediment thicknesses of up to 4 km were determined from a coincident multichannel reflection line. Beneath the sediments, velocities increase from about 5.5 to 6.3 km·s−1 at 8 km depth, then increase from 6.5 to 6.7 km·s−1 at 18 km depth. Below this depth, the lower crust is partly constrained by Moho wide-angle reflections at the three receiving sites, which indicate a lower crust velocity of 6.8–6.9 km·s−1 and a Moho depth of 26–28 km. The crustal velocity structure is generally similar to that in southern Queen Charlotte Sound. It is in contrast to the velocity structure across Hecate Strait to the north, where a prominent mid-crust interface at ~15 km depth was observed. Seismic velocity models of the continental crust provide constraints that can be used in modelling gravity data to extend structures across the ocean–continent boundary. Along the profile just north of the Queen Charlotte triple junction, the gravity "edge effect" is very subdued, with maximum anomalies of < mGal (1 mGal = 10−3 cm·s−2). To satisfy the gravity data along this profile, the modelled crustal thickness must decrease to oceanic values (5–6 km) over a horizontal distance of 75 (±10) km, which gives a Moho dip of about 14°. Farther north, refraction models across Hecate Strait provide similar constraints for gravity modelling; the gravity data indicate horizontal transition distances from thick to thin crust of 45 (±10) km, comparable with, but slightly smaller than, those nearer the triple junction, and Moho dips at an angle of 18–22°. The greater thinning near the triple junction is consistent with mass flux models in which ductile flow in the lithosphere is induced by the relative motion between oceanic and continental plates.

Introduction: geological and geophysical studies in the Trans-European Suture Zone

1997 ◽  
Vol 134 (5) ◽  
pp. 585-590 ◽  
Author(s):  
T. C. PHARAOH ◽  
R. W. ENGLAND ◽  
J. VERNIERS ◽  
A. ŻELAŹNIEWICZ
Keyword(s):  
Heat Flow ◽  
Seismic Data ◽  
Lithospheric Mantle ◽  
Western Europe ◽  
Velocity Structure ◽  
Sedimentary Basins ◽  
Suture Zone ◽  
Crystalline Basement ◽  
East European ◽  
Thick Crust

The Trans-European Suture Zone (TESZ) is the boundary between ancient Precambrian lithosphere of the East European Craton (EEC) and the younger lithosphere beneath the latest Neoproterozoic–Palaeozoic mobile belts of western Europe. The former is characterized by a thick crust (c. 45 km), low heat flow and a tectono-thermal age of about 3000 to 800 Ma, the latter by a thinner crust (c. 30 km), higher heat flow and a tectonothermal age of 560 to 290 Ma. These contrasting types of crust were juxtaposed during the Caledonian and Variscan orogenic episodes. The crystalline basement of the TESZ is largely concealed by sedimentary basins controlled by the reactivation of structures within the suture zone during Permian–Mesozoic extension and Cenozoic inversion. The pre-Permian evolution of the craton and the mobile belts, and the location of the sutures, is inferred from isolated outcrops, hundreds of boreholes and geophysical evidence. Existing seismic data demonstrates that the TESZ is rather narrow and has an expression at all levels of the lithosphere and deep into the asthenosphere. Teleseismic studies have demonstrated that the differences in the velocity structure of the asthenospheric and lithospheric mantle across the TESZ persist to depths of c. 400 km (Zielhus & Nolet, 1994).

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

2021 ◽  
Author(s):  
Evgenia Salin ◽  
Jeremy Woodard ◽  
Krister Sundblad
Keyword(s):  
Baltic Sea ◽  
Short Distance ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Drill Core ◽  
The Baltic Sea ◽  
Baltic Sea Region ◽  
Drill Site ◽  
Southwestern Margin ◽  
The Baltic

AbstractGeological investigations of a part of the crystalline basement in the Baltic Sea have been performed on a drill core collected from the depth of 1092–1093 m beneath the Phanerozoic sedimentary cover offshore the Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with the SIMS U–Pb zircon method. Inherited zircon cores from this migmatized granodioritic orthogneiss have an age of 1854 ± 15 Ma. Its chemical composition and age are correlated with the oldest generation of granitoids of the Transscandinavian Igneous Belt (TIB), which occur along the southwestern margin of the Svecofennian Domain in the Fennoscandian Shield and beneath the Phanerozoic sedimentary cover on southern Gotland and in northwestern Lithuania. It is suggested that the southwestern border of the Svecofennian Domain is located at a short distance to the SW of the investigated drill site. The majority of the zircon population shows that migmatization occurred at 1812 ± 5 Ma, with possible evidence of disturbance during the Sveconorwegian orogeny.

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