Seismogenic Delaminated Continental Lithosphere Under the Eastern Carpathian Bend Zone, Romania
M. A. Fillerup, J. H. Knapp, and C. C. Knapp
Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
Two lithosphere-scale, explosive-source seismic reflection profiles (DRACULA I and DACIA PLAN), inclusive of the hinterland and foreland of the Romanian Eastern Carpathians, provide new evidence for the geodynamic origin of the Vrancea Seismogenic Zone of Romania. These data show the geometry of thinned orogenic crust beneath the mountain belt and a newly identified ‘missing’ lower crustal section. Crustal thicknesses inferred from these data based on reflectivity show a 38-45 km crust below the Transylvanian basin abruptly shallowing to 32 km for ~120 km beneath the fold and thrust belt of the main Carpathian orogen and thickening again to 38-42 km crust in the Focsani foreland. The geometry of the Vrancea Seismogenic Zone (30x70x200 km) corresponds to the geometry of the missing lower crustal section to the NW and suggests the root of the Eastern Carpathians has been delaminated and is now failing brittlely in the upper mantle. If correct this new insight into delamination could provide means of generating mantle seismicity without necessitating convergent tectonics. Moreover, the absence of any through-going, dipping crustal-scale boundaries along this composite lithospheric transect would appear to preclude subduction as an explanation for mantle seismicity in the Eastern Carpathians, contrary to historically published data.
AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas