Dominant structures of Inner Western Carpathians: A tectonic model based on seismic and gravity data of project Celebration 2000 -transect CEL-05

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Vozلr, Jozef۱; Bielik, Miroslav۲; Guterch, Aleksander۳; Grad, Marek۴; Csicsay, Kristian۲; Hladk‎, Juraj۲
Holding Date 15 September 2008

Profile CEL05 is important for tectonic relationships between the Carpathian-Pannonian region and the East European Craton. This region is part of a very complex collisional environment between the EU and ADRIA plates. The identification and determination of the extent of these terranes is controversial, because they have been subducted/obducted, and/or translated during subsequent events. Studies of the Carpathian-Pannonian region have interpreted it to consist of the Alpine-Carpathian-Pannonian and TISIA-DACIA that are separated by the Mid-Hungarian line. The southern part of profile CEL05 primarily crosses the ALCAPA that extends up to the Pieniny Klippen belt (PKB), which represents the tectonic boundary between Inner (IC) and Outer (OC) Carpathian units. The first 250 km of the profile lies in the Pannonian basin where the crust is thin (~25 km), and our velocity model indicates the area is covered by 2-3 km of Tertiary sedimentary strata, which is in agreement with estimates based on drilling and seismic data. The portions of the Pannonian basin and the Carpathians traversed by profile CEL05 have been divided into the following structural units: 1.the Tisia block south of the Mid-Hungarian line; 2. central unit consisting of the Pelso structural block and the Alpine-type nappe structures of the IC; 3.northern unit consisting of the OC and their foredeep north of the PKB. The bottom of the nappe structures is probably coincident with the bottom of the second crustal layer. To the south in the Bukk Mts. the lens of higher velocity rocks (6.45 km/s) can be connected to the occurrence of subvolcanic bodies associated with the Mátra volcano. Just north of this is probably linked with the Diósjenُ line and reflects the internal structure of the Inner Carpathian (IC) units. The northern boundary of the IC is delimited by the PKB, which is a prominent regional shear zone that dips southward at 35-40° and has also experienced left-lateral displacement. The PKB can be traced to a depth of 12 kms as a narrow belt of low velocities.
The continuation of the PKB can be interpreted to be approximately parallel to the 6.05 km/s velocity isoline within the second layer and reaches the boundary between second and third layers at a depth of ~20 km. The PKB has been interpreted to be related to a southward dipping suture zone. There is no indication of south dipping interfaces below a depth of ~20 km, but the detachment could be nearly horizontal beginning at this depth. Based on seismic and gravity modeling indicates significant structure of PKB, which represents the surface boundary between the Outer and IC but as well as in the depth the boundary between the EU platform and ALCAPA. In the IC it can be observed clearly the anomalous seismic and gravity body - Alpine granitoids. Darnó line represents significant density boundary between Gemericum and Bukkicum.