HR: 0830h
AN: T31D-0862    [PDF]
TI: Crustal Constraints on the Origin of Mantle Seismicity in the Vrancea Zone, Romania: The Case for Active Continental Lithospheric Delamination
AU: * Knapp, J H
EM: knapp@geol.sc.edu
AF: Department of Geological Sciences University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Knapp, C C
EM: camelia@geol.sc.edu
AF: Department of Geological Sciences University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Raileanu, V
AF: National Institute for Earth Physics, Magurele, Bucharest, MG-2 Romania
AU: Mocanu, V
AF: Faculty of Geology and Geophysics University of Bucharest, 6 Traian Vuia St., Bucharest, 70139 Romania
AU: Matenco, L
AF: Faculty of Earth Sciences Vrije Universitet, De Boolelan 1085, Amsterdam, 1081 HV Netherlands
AU: Dinu, C
AF: Faculty of Geology and Geophysics University of Bucharest, 6 Traian Vuia St., Bucharest, 70139 Romania
AU: Anderson, E
AF: Department of Geological Sciences University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Mucuta, D
AF: Department of Geological Sciences University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AB: The Vrancea zone of Romania constitutes one of the most active seismic zones in Europe, where intermediate-depth (70-200 km) earthquakes of magnitude in excess of M=7.0 occur with relative frequency in a geographically restricted area within the 110 degree bend region of the southeastern Carpathian orogen. Geologically, the Vrancea zone is characterized by (a) a laterally-restricted, steeply NW-dipping seismogenic volume (30x70x200 km), situated beneath (b) thickened continental crust within the highly arcuate bend region of the Carpathian orocline, and (c) miscorrelation of hypocenters with the position of an inferred Miocene suture zone in the Carpathian hinterland. Geologic data from petroleum exploration in the Eastern Carpathians, and reprocessing of industry seismic data from the Carpathian foreland indicate that (1) crust of continental affinity extends significantly westward beneath the thrust nappes (Sub-Carpathian, Marginal Folds, and Tarcau) of the Eastern Carpathians, (2) Cretaceous to Miocene strata of continental affinity can be reconstructed westward to a position now occupied by the Transylvanian basin, and (3) geologic structure in the Carpathian foreland (including the Moho) is sub-horizontal directly to the east and above the Vrancea seismogenic zone. Taken together, these geologic relationships imply that the Vrancea zone occupies a region overlain by continental crust and upper mantle, and does not appear to originate from a subducted oceanic slab along the length of the Carpathian orogen. Accordingly, the Vrancea zone appears to be a unique place to establish evidence for active lithospheric delamination as opposed to relic subduction.
DE: 0905 Continental structures (8109, 8110)
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 8102 Continental contractional orogenic belts
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting