HR: 1340h
AN: T53B-0504    [Abstracts]
TI: Echoes from the Transylvanian Lithosphere: Preliminary Results From the DRACULA I Profile and Implications for Geodynamics of the Vrancea Zone
AU: * Fillerup, M A
EM: mfillerup@geol.sc.edu
AF: Department of Geological Sciences, Unversity of South Carolina, 701 Sumter St. EWS 617, Columbia, SC 29208 United States
AU: Knapp, J H
EM: jknapp@geol.sc.edu
AF: Department of Geological Sciences, Unversity of South Carolina, 701 Sumter St. EWS 617, Columbia, SC 29208 United States
AU: Knapp, C C
EM: cknapp@geol.sc.edu
AF: Department of Geological Sciences, Unversity of South Carolina, 701 Sumter St. EWS 617, Columbia, SC 29208 United States
AU: Munteanu, L
AF: National Institute for Earth Physics, Bucharest-Magurele, P.O. Box MG-2 , Bucharest, 4930117 Romania
AU: Mocanu, V
AF: Faculty of Beology and Geophysics, University of Bucharest, 6 Train Vuia St. , Bucharest, 70139 Romania
AU: Raileanu, V
AF: National Institute for Earth Physics, Bucharest-Magurele, P.O. Box MG-2 , Bucharest, 4930117 Romania
AB: Preliminary examination of new deep seismic reflection data in the Transylvanian Basin of Romania, collected through Project DRACULA, reveals strongly layered subhorizontal reflectivity throughout the middle and lower crust, as well as the upper mantle. Collected with 20 kg shots every 1 km recorded to 60 s by a 32-km active spread (640 channels at 50 m) with Reftek-125 seismometers in roll-along mode, the DRACULA I profile consists of a 240-km transect extending NW from the Vrancea Seismogenic Zone. Single-fold shot gathers repeatedly image (1) a strong reflector (basement cover contact?) at around 1.6-2.0 s TWTT (~3-5 km) within the Transylvanian basin, (2) strong sub-horizontal reflections beneath the Persani Mountains that may represent either structural elements or igneous intrusive features (3) suhorizontal to gently E-dipping reflections beneath the Eastern Carpathians at 6.0-8.0 s TWTT that may be the downdip continuation of regional detachment faults of the Carpathian nappes, and (4) strong sub-horizontal and laterally continuous reflectivity, beginning at 6-10 s TWTT (15-25 km) and continuing downward in some cases to as much as 30 s (greater than 100 km), clearly within the upper mantle. An interpretation for the strongly layered upper mantle, and the absence of a clear break in reflectivity across the Moho is still premature, but it would appear that geologic processes in the Transylvanian mantle have imparted reflection fabrics similar to those seen in the lower crust on many deep reflection profiles. Of particular significance is the exclusively and pervasively subhorizontal geometry of reflective layering throughout the Transylvanian crust and upper mantle, seemingly precluding the presence of a former subduction zone anywhere within the 240-km trace of the profile. These observations would appear to argue against a subduction origin for intermediate depth seismicity in the Vrancea Zone.
DE: 8100 TECTONOPHYSICS
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting