HR: 1340h
AN: T43B-1401    [Abstracts]
TI: Seismic Structure of the Eastern Black Sea Basin
AU: * Scott, C L
EM: cls203@noc.soton.ac.uk
AF: National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH United Kingdom
AU: Shillington, D J
EM: djshill@noc.soton.ac.uk
AF: National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH United Kingdom
AU: Minshull, T
EM: tmin@noc.soton.ac.uk
AF: National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH United Kingdom
AU: White, N
EM: nwhite@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Edwards, R
EM: rae@noc.soton.ac.uk
AF: National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH United Kingdom
AB: Although the Black Sea is one large depositional structure today, previous studies have shown that the basin can be divided into two sub-basins, which have different tectonic histories. There is a general consensus on the formation history of the Western Black Sea Basin but there is little agreement on the history of the Eastern Black Sea. In March 2005 we collected a series of onshore-offshore, wide-angle seismic refraction/reflection profiles throughout the basin to sample the crustal structure. Four lines were surveyed; Line 1 was a 470 km profile, shot along strike through the centre of the basin, Lines 3 and 4 were dip lines shot across the Mid-Black Sea High and one dip line (Line 2) was shot further to the east. Data quality is very good and deep arrivals can be typically detected to 100 km offset. These data will be combined with co-incident industry reflection profiles to constrain the extensional evolution of the Eastern Black Sea Basin. We present data from Line 1, which has been modelled to investigate the velocity structure of the basin. Line 1 has 34 ocean bottom seismometers, spaced at ~14 km, deployed along the profile with an additional seven seismometers deployed on land. The seismic source was an air-gun array with a total source volume of 3140 cu.in and the line was shot at a spacing of 60 s, equivalent to a spatial interval of about 120 m. A combination of ray-tracing and first-arrival seismic tomography has been used to create a 2D velocity model through the crust. The model shows that the basin has a thick sedimentary package (up to ~10 km thick) with velocities ranging from 1.6 - 4.2 km/s. These overlay a crystalline crust with velocities of 4.8 - 7.2 km/s, which thins to ~8 km thick in the deepest part of the basin. The model indicates the presence of a low velocity zone near the base of the sediment package. This anomalous layer stretches across most of the profile, with velocities as low as 3.1 ñ 0.12 km/s compared with sediment velocities of 3.9 km/s above. The most likely explanation for these low velocities is over pressurisation of pore-fluids leading to under-compaction of the sediments.
DE: 3001 Back-arc basin processes
DE: 3025 Marine seismics (0935, 7294)
DE: 7270 Tomography (6982, 8180)
DE: 8105 Continental margins: divergent (1212, 8124)
SC: Tectonophysics [T]
MN: Fall Meeting 2005