The Tornquist Zone northwest of the Carpathians: an intraplate pseudosuture

Deep seismic surveys, teleseismic tomography and other geophysical studies all suggest that the Tornquist Zone is an old plate boundary or suture, but geological relations indicate an intraplate origin and Permo-Carboniferous to Early Tertiary age. From the North Sea, the Tornquist Zone is developed on the Baltica side of the Caledonian collisional suture (Thor suture, for med by closure of the Thor Ocean/Tornquist Sea). To satisfy both geological and geophysical data, a new model is presented for the formation of the La te Carboniferous-Early Permian NW-SE fault zones that dismember the norther n Variscan foreland and outline its border against the Baltic Shield and Ea st European Platform. They are interpreted to have formed in relation to de ep, normal/oblique sense, Wernicke-type, listric detachments that sole belo w the rigid lithosphere. Detachment induced attenuation of the foreland's C aledonian and Proterozoic lithosphere triggered endogenic processes that ev entually produced a more shallow asthenosphere-lithosphere boundary and a l evelled, more high lying, seismic Moho. The thick lithosphere below the Bal tic Shield and East European Platform was sheltered by a NE-dipping boundar y detachment, which absorbed also ensuing extension and compression. When, by Early Tertiary, the inverted Tornquist Zone rose from the proximal part of its hanging wall, a strong contrast had been established between the att enuated and reset lithosphere southwest of the Tornquist Zone, and the unaf fected, thick and cool lithosphere of the neighbouring Shield and Platform.