Reconstruction of Cretaceous rifts incorporated in the Outer West Carpathian wedge by balancing

Two balanced cross-sections were constructed through the Outer Carpathians of Poland in order to restore the Early Cretaceous rifts. The rift fill is incorporated into the Tertiary Carpathian accretionary wedge. The data comp iled for this study confirm that the Early Cretaceous rifting in the Silesi an Basin area was followed by Late Cretaceous-Paleocene basin inversion. Eo cene pelagic deposition, and Oligocene syn orogenic deposition. The origina l width of the Silesian Basin is about 130-138 km. The overall wedge shorte ning ranges between 31 and 58% with 57 and 58% in the Silesian Nappe. The r ifting commenced at the Jurassic/Cretaceous boundary and formed the horst a nd graben structures defined by NW-SE striking normal faults. Portions of t he horsts become emergent at various times during rifting stages. Sedimenta tion rates in the grabens varied around 4.7. 2.1 and 1.3 cm/ka during three rifting stages, while sedimentation rates on their slopes varied around 0. 0-1.26 and 0 cm/ka. The altitude difference between horst tops and graben f loors did not exceed 2 km. The reconstructed widths of the horsts range bet ween 17.5 and 18.3 km. The reconstructed widths of several grabens in both cross-sections have values 14.5, 45.7. 57.7 and 79.3 km. The rifting-relate d extension. calculated from fault-striae data, was NE-SW directed. Sometim es, the very low (sigma (2)-sigma (3))/(sigma (1)-sigma (3)) stress ratio O f the driving stress configuration resulted in polydirectional extension wh en the value decreased below 0.1. (C) 2001 Published by Elsevier Science Lt d.