Crustal structure of the Trans-European Suture Zone in Central Poland — reinterpretation of the LT-2, LT-4 and LT-5 deep seismic sounding profiles

Abstract

The paper gives a reinterpretation of data from three deep seismic sounding profiles — LT-2, LT-4 and LT-5 — acquired in 1974–1979 between the Precambrian East European Craton (EEC) and the Palaeozoic Platform (PP) in Central Poland. Good quality seismic records in the distance interval from 50–90 to 200–280 km were the input data for the modelling of the crustal and uppermost mantle structure. Clear first arrivals and later phases of waves reflected/refracted from the crustal and the Moho boundaries were interpreted using a two-dimensional (2-D) ray tracing technique. In general, the crustal thickness along the three profiles varies from 30–35 km in the Palaeozoic platform area, to 42–44 km in the Polish part of the EEC, being 35–40 km in the transition zone between the PP and the EEC. In the transition area, the P-wave velocity is very low (Vp <6.0 km/s) down to depths of 15–18 km, indicating that a very thick succession of sedimentary, metamorphosed or volcanic origin rocks is present there. All three 2-D models of the crust are discussed together with results obtained 20–30 years ago, particularly taking into account the difference in interpretation methods and new computation possibilities. Jointly with recent seismic studies along the profiles LT-7 and TTZ, as well as the POLONAISE’97 profiles P1–P4, the reinterpreted old profiles provide a collection of crustal models of the TESZ in Poland.