Department of Lithospheric Research IG PAS

Crustal structure across the Teisseyre-Tornquist Zone offshore Poland based on a new refraction/wide-angle reflection profile and potential field modelling

2022-03-22T13:20:49Z

Crustal structure across the Teisseyre-Tornquist Zone offshore Poland based on a new refraction/wide-angle reflection profile and potential field modelling Janik, Tomasz; Wójcik, Dariusz; Ponikowska, Małgorzata; Mazur, Stanisław; Skrzynik, Tymon; Malinowski, Michał; Hübscher, Christian This paper presents a 230-km long refraction/wide-angle reflection profile that was acquired in the southern Baltic Sea across the Teisseyre-Tornquist Zone (TTZ), the boundary between the East European Craton (EEC) and the West European Platform (WEP). This profile is nearly parallel to the western Polish coast, halfway between Poland and the Danish island of Bornholm. The data acquisition was conducted with 15 ocean bottom seismometers (OBS) and 2 land stations. We applied the trial-and-error iterative ray-tracing technique using all identified seismic phases to derive crustal models by minimizing misfit between calculated and observed P-wave travel-times for individual layers. Final velocity model was further verified by forward potential field modelling, testing various P-wave velocity (Vp) to density relationships. The Moho boundary was inferred at 33-38 km depth, deepening towards the EEC, with the local ~3 km rise in a 40-km-wide zone north of the Caledonian Deformation Front, corresponding to the elevated middle-crust velocities Vp >6.5 km/s. The lower and middle crust are mostly continuous along the BalTec profile with only minor perturbations between the EEC and WEP. Nevertheless, the thickness of these crustal layers is poorly constrained by seismic data along the SW section of the profile. In contrast, the upper crust and sedimentary cover can be subdivided into three domains, corresponding, from the NE to SW, to the EEC, TTZ and WEP, respectively. The EEC is characterised by the flat top of the basement, uniformly inclined towards the SW. The TTZ shows rapid thinning of cratonic upper crust and thickening of sedimentary layer. The WEP reveals, despite limited seismic coverage, a 13-km thick sedimentary overburden. The lateral changes of seismic structure within the upper crust and sedimentary cover along the BalTec profile can be attributed to protracted phases of late Palaeozoic-Mesozoic extension punctuated by the Carboniferous and Late Cretaceous inversion phases.

Full-length seismic sections for OBH 15 - 13. Geological cross-sections from the southern Baltic Sea. Examples of the selected tested models. Comparison of the P_n and P_MP traveltimes for the tested models.

2022-03-16T11:01:07Z

Full-length seismic sections for OBH 15 - 13. Geological cross-sections from the southern Baltic Sea. Examples of the selected tested models. Comparison of the P_n and P_MP traveltimes for the tested models.

Seismic refraction profiles from the southern Baltic Sea and onshore Poland

2022-03-16T10:56:40Z

Seismic refraction profiles from the southern Baltic Sea and onshore Poland

Lithospheric structure along wide-angle seismic profile GEORIFT 2013 in Pripyat–Dnieper–Donets Basin (Belarus and Ukraine)

2021-11-19T13:12:31Z

Lithospheric structure along wide-angle seismic profile GEORIFT 2013 in Pripyat–Dnieper–Donets Basin (Belarus and Ukraine) Starostenko, V.; Janik, Tomasz; Yegorova, T.; Czuba, Wojciech; Środa, Piotr; Lysynchuk, D.; Aizberg, R.; Garetsky, R.; Karataev, G.; Gribik, Y.; Farfuliak, L.; Kolomiyets, K.; Omelchenko, V.; Komminaho, K.; Tiira, T.; Gryn, D.; Guterch, Aleksander; Legostaeva, O.; Thybo, H.; Tolkunov, A. The GEORIFT 2013 (GR'13) WARR (wide-angle reflection and refraction) experiment was carried out in 2013 in the territory of Belarus and Ukraine with broad international co-operation. The aim of the work is to study basin architecture and deep structure of the Pripyat–Dnieper–Donets Basin (PDDB), which is the deepest and best studied Palaeozoic rift basin in Europe. The PDDB is located in the southern part of the East European Craton (EEC) and crosses Sarmatia—one of the three segments of the EEC. The PDDB was formed by Late Devonian rifting associated with domal basement uplift and magmatism. The GR’13 extends in NW–SE direction along the PDDB strike and crosses the Pripyat Trough (PT) and Dnieper Graben (DG) separated by the Bragin Uplift (BU) of the basement. The field acquisition along the GR'13 (of 670 km total length) involved 14 shots and recorders deployed every ∼2.2 km for several shot points. The good quality of the data, with first arrivals visible up to 670 km for several shot points, allowed for construction of a velocity model extending to 80 km depth using ray-tracing modelling. The thickness of the sediments (Vp < 6.0 km s−1) varies from 1–4 km in the PT, to ∼5 km in the NW part of the DG, to 10–13 km in the SE part of the profile. Below the DG, at ∼330–530 km distance, we observed an upwarping of the lower crust (with Vp of ∼7.1 km s−1) to ∼25 km depth that represents a rift pillow or mantle underplate. The Moho shallows southeastwards from ∼47 km in the PT to 40–38 km in the DG with mantle velocities of 8.35 and ∼8.25 km s−1 in the PT and DG, respectively. A near-horizontal mantle discontinuity was found beneath BU (a transition zone from the PT to the DG) at the depth of 50–47 km. It dips to the depth of ∼60 km at distances of 360–405 km, similar to the intersecting EUROBRIDGE’97 profile. The crust and upper mantle structure on the GR'13 may reflect varying intensity of rifting in the PDDB from a passive stage in the PT to active rifting in the DG. The absence of Moho uplift and relatively thick crystalline crust under the PT is explained by its tectonic position as a closing unit of the PDDB, with a gradual attenuation of rifting from the southeast to the northwest. The most active stage of rifting is evidenced in the DG by a shallower Moho and by a presence of a rift pillow caused by mafic and ultramafic intrusions during the active phase. The junction of the PT and the DG (the BU) locates just at its intersection with the NS regional tectonic zone Odessa-Gomel. Most likely, the ‘blocking’ effect of this zone did not allow for further propagation of active rifting to the NW.