HR: 08:30h
AN: T51E-03    [Abstracts]
TI: Investigating the Asymmetry of Northern North Atlantic Volcanic Continental Margins
AU: * Smith, L K
EM: lsmith@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge Madingley Rise, Cambridge, CB4 3PJ United Kingdom
AU: White, R S
EM: rwhite@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge Madingley Rise, Cambridge, CB4 3PJ United Kingdom
AB: The Hatton Bank continental margin is a typical example of the volcanic margins present in the northern North Atlantic where voluminous magmatism occurred at the time of continental break-up. The upper crust exhibits characteristically large volumes of extruded lava imaged as seaward-dipping reflectors, which have in the past proved problematic for seismic imaging of the deeper crustal structure. The integrated Seismic Imaging and Modelling of Margins (iSIMM) project recorded profiles in 2002 designed to map specifically the poorly constrained lower crustal structure in this region. 29 four-component ocean-bottom seismometers (OBS) were deployed along a strike line over the region of thickest extrusive and intruded igneous material; 53 OBS were deployed through the mid-point of the strike line, along a dip line extending from the stretched continental crust of the Hatton Basin into the fully oceanic crust of the Iceland Basin. We present a new seismic velocity model for the Hatton Bank volcanic continental margin. Joint wide-angle refraction and reflection tomography was used to determine the seismic velocity structure and depth to Moho across the continent-ocean transition (COT) in both the dip and strike directions. The lower crust beneath the margin exhibits elevated crustal velocities in the range of 7.0-7.4 km/s, which represent new igneous material added to the lower crust in this region at the time of continental break-up. The iSIMM survey is located close to the site of a previous survey carried out in 1986. A comparison of the 1986 results and the results from the 1996 SIGMA survey carried out on the conjugate southeast Greenland margin show a marked asymmetry in crustal structure: the Greenland margin appears to have a COT stretched over ~ 150 km compared to the narrower COT of the Hatton Bank margin, which extends for only ~ 50 km. The new iSIMM survey results provide a refined estimate of crustal structure of the Hatton Bank margin and improved constraints on the intrusive and extrusive igneous components produced during continental break-up in the early Tertiary. Using the new results from the Hatton Bank margin we present an updated comparison of the conjugate margins and investigate the degree of asymmetry in this region of the northern North Atlantic.
DE: 0935 Seismic methods (3025, 7294)
DE: 7270 Tomography (6982, 8180)
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 9325 Atlantic Ocean
SC: Tectonophysics [T]
MN: Fall Meeting 2005