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Crustal structure below the Polish Basin: Is it composed of proximal terranes derived from Baltica? 总被引：2，自引：2，他引：2
The large-scale seismic refraction and wide-angle reflection experiment POLONAISE'97 together with LT-7 and TTZ profiles carried out with the most modern techniques gave a high resolution of crustal structure of the Trans-European Suture Zone (TESZ) in NW and central Poland. The results of seismic investigations show the presence of relatively low velocity rocks (Vp < 6.1 km/s) down to a depth of 20 km beneath the Polish Basin (PB), and a high velocity lower crust (Vp = 6.8–7.3 km/s). The crustal thickness in the TESZ is intermediate between that of the East European Craton (EEC) to the northeast (40–45 km) and that of the Variscan crust (VB) to the southwest ( 30 km). Velocities in the uppermost mantle are relatively high (Vp = 8.25–8.45 km/s). The crust is three-layered with substantial differences in the velocities and thickness of individual layers. The area of the TESZ in NW and central Poland can be divided into at least two crustal blocks (terranes), called here Pomeranian Unit (PU, in the northwest) and Kuiavian Unit (KU, in the southeast). The postulated boundary between KU and PU is rather sharp at particular levels of the crust. Velocity distribution in the middle and lower crystalline crust in the TESZ area resemble values recognized in the EEC area, the fundamental difference being the much smaller thickness of both these layers. Our hypothesis/speculation is that the attenuated lower and middle crust of the TESZ belong to proximal terranes built of the EEC crust detached in the southeast and re-accreted to the EEC due to the process of anti-clockwise rotation of the Baltica paleocontinent during the Ordovician–Early Silurian. 相似文献
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Tomasz Janik Marek Grad Aleksander Guterch Ryszard Dadlez Jukka Yliniemi Timo Tiira G. Randy Keller Edward Gaczy&#x;ski CELEBRATION Working Group 《Tectonophysics》2005,411(1-4):129-156
The large-scale CELEBRATION 2000 seismic experiment investigated the velocity structure of the crust and upper mantle between western portion of the East European Craton (EEC) and the eastern Alps. This area comprises: the Trans-European Suture Zone, the Carpathian Mountains, the Pannonian Basin and the Bohemian Massif. This experiment included 147 chemical shots recorded by 1230 seismic stations during two deployments. Good quality data along 16 main and a few additional profiles were recorded. One of them, profile CEL03, was located in southeastern Poland and was laid out as a prolongation of the TTZ profile performed in 1993. This paper focuses on the joint interpretation of seismic data along the NW–SE trending TTZ–CEL03 transect, located in the central portion of the Trans-European Suture Zone. First arrivals and later phases of waves reflected/refracted in the crust and upper mantle were interpreted using two-dimensional tomographic inversion and ray-tracing techniques. This modelling established a 2-D (quasi 3-D) P-wave velocity lithospheric model. Four crustal units were identified along the transect. From northwest to southeast, thickness of the crust varies from 35 km in the Pomeranian Unit (NW) to 40 km in the Kuiavian Unit, to 50 km in the Radom–Łysogóry Unit and again to 43 km in the Narol Unit (SE). The first two units are thought to be proximal terranes detached from the EEC farther to the southeast and re-accreted to the edge of the EEC during the Early Palaeozoic. The origin of the remaining two units is a matter of dispute: they are either portions of the EEC or other proximal terranes. In the area of the Polish Basin (first two units), the P-wave velocity is very low (Vp < 6.1 km/s) down to depths of 15–20 km indicating that a very thick sedimentary and possibly volcanic rock sequence, whose lower portion may be metamorphosed, is present. The velocity beneath the Moho was found to be rather high, being 8.25 km/s in the northwestern portion of the transect, 8.4 km/s in the central sector, and 8.1 km/s in the southeastern sector. 相似文献
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2-D seismic tomographic and ray tracing modelling of the crustal structure across the Sudetes Mountains basing on SUDETES 2003 experiment data 总被引：2，自引：3，他引：2
Mariusz Majda&#x;ski Marek Grad Aleksander Guterch SUDETES Working Group 《Tectonophysics》2006,413(3-4):249-269
The seismic data obtained during SUDETES 2003 experiment are analysed, and detailed crustal structure for profiles S02, S03 and S06 is presented using three different 2-D techniques: (1) “smooth” tomography of refracted waves travel times, (2) ray tracing of reflected and refracted waves, and (3) joint velocity and depth of reflector tomographic inversion. In spite of different interpretation techniques used, the models of the crustal structure show common characteristic features. The low velocity (Vp < 4 km/s) sedimentary layer was documented in the northeastern part of the study area. The topmost basement has in general a velocity of 5.8–6.0 km/s, and velocities at ca. 20 km depth are 6.15–6.25 km/s. The strong reflecting boundaries were found at 20–23 and 25–28 km depth with a velocity contrast about 0.4 km/s, and the highest velocities in the lowermost crust are 6.8–7.2 km/s. In general, the crust of the Bohemian Massif is slightly thicker (33–35 km) than in the northern part of the area. Velocities beneath Moho are relatively low, of 7.95 km/s. On the basis of well recorded reflected waves, mantle reflectors were discovered in the depth interval ca. 40–70 km. Apart of new results for the geology and tectonics of the area, some conclusion could be made about different techniques used. In the 2-D case the “clasical” ray tracing method with using all correlated phases gives the most adequate model of the structure, because of full, manual control of the model creation. The “smooth” first arrival travel times tomography, although very fast, is not satisfactory enough to describe the complex structure. So, the best candidate in 3-D case seems to be travel time tomography for both refracted and reflected waves in multi-layers models. 相似文献
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M. Wilde-Piórko W. H. Geissler J. Plomerová M. Grad V. Babuška E. Brückl J. Cyziene W. Czuba R. England E. Gaczyński R. Gazdova S. Gregersen A. Guterch W. Hanka E. Hegedűs B. Heuer P. Jedlička J. Lazauskiene G. Randy Keller R. Kind K. Klinge P. Kolinsky K. Komminaho E. Kozlovskaya F. Krüger T. Larsen M. Majdański J. Málek G. Motuza O. Novotný R. Pietrasiak Th. Plenefisch B. Růžek S. Sliaupa P. Środa M. Świeczak T. Tiira P. Voss P. Wiejacz 《Studia Geophysica et Geodaetica》2008,52(3):439-448
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M. Malinowski M. Grad A. Guterch E. Takcs Z.
liwi&#x;ski L. Antonowicz E. Iwanowska G.R. Keller E. Heged&#x;s 《Tectonophysics》2007,439(1-4):89-106
The extent of the Variscan deformation front is one of the key problems of the regional geology of the Central European Permian Basin system, particularly in its Polish part. Conventional reflection seismics usually fails to produce a satisfactory image of the pre-Permian strata due to the shielding effect of Zechstein (Upper Permian) evaporites. Thus we used a novel seismic acquisition technique to study the base of the Permian complex and its Variscan basement. In the GRUNDY 2003 experiment we combined wide-angle reflection–refraction measurements with the near-vertical reflection seismics by the use of the constant geophone array with dense (100 m) receiver spacing occupying 50-km long profile. 3D design of the experiment, covering 50 × 10 km area, helped in eliminating the effect of out-of-plane propagations and local inhomogeneities. An effective integration of traveltime tomography, CDP reflection processing and prestack depth migration of wide-angle reflections applied to our data, allowed us to present the model in which we deduced the contact zone of the Variscan overthrust structure (Variscan front) with its molasse-filled foredeep. The latter might be a gas-generation zone, which is of a great importance for hydrocarbons prospecting in this area. 相似文献