Abstract
Results of a depth-to-basement study are presented for the East European Craton and the Teisseyre-Tornquist Zone (TTZ) in Poland. The terrestrial gravity data are inverted for the top of the Paleoproterozoic basement and, independently, for the top of the Ediacaran using seismic horizons from the PolandSPAN™ seismic survey and well tops as input depth measurements. The depth to the Ediacaran modelling was additionally extended to cover the Łysogóry Block and northern Małopolska Block. The results are visualised as isobath maps for the top of the Paleoproterozoic basement and top of the Ediacaran and an isopach map for the Ediacaran, supplemented with qualitative structural interpretation based on gravity and magnetic data. The results of modelling show a smooth crystalline basement slope within the TTZ with the top of the Paleoproterozoic basement uniformly descending south-westwards by 10–14 km. The thickness of the Ediacaran in SE Poland increases in the same direction to more than 10 km within the TTZ. Such a crustal architecture, in combination with the earlier documented Moho elevation of 4–6 km, reveals significant thinning of the Paleoproterozoic crust within the TTZ to form a crustal necking zone due to the Ediacaran rifting. A smooth geometry of the top of basement along with the lack of basement-rooted faults suggests a ductile mode of crustal thinning during rifting of Rodinia. Moreover, the development of the NW–SE-oriented rift, a precursor of the Tornquist Ocean, was associated with rifting in a NE–SW direction parallel to the Orsha-Volyn Rift.
Highlights
The south-western slope of the East European Craton (EEC) and the Teisseyre-Tornquist Zone (TTZ) have a key significance for understanding the transition from old Precambrian Europe in the east to younger Palaeozoic Europe in the west (Fig. 1; e.g., Pharaoh 1999; Winchester et al.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.2002; Guterch et al 2010)
The top of the Paleoproterozoic crystalline basement horizon was interpreted in this study as corresponding to seismic P-wave velocities of 6.0–6.1 km/s
To compare the present results to the seismicderived basement models by Majdański (2012) and Grad and Polkowski (2016), we subtracted their grids from the top of the Paleoproterozoic crystalline basement calculated in this study (Fig. 11)
Summary
The gravity data were inverted for the top of the Paleoproterozoic basement and separately for the top of the Ediacaran using reflection seismic horizons and well tops for depth calibration. The area of the top of the Paleoproterozoic basement modelling (Fig. 2) was equivalent to the extent of the PolandSPANTM seismic survey (Krzywiec et al 2014).
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