Crustal structure of the Makarov Basin, Arctic Ocean determined by seismicrefraction

Wide-angle seismic reflection/refraction data, recorded on ten seismographs from five large explosive charges, clearly define the crustal and upper ma ntle velocities of the Makarov Basin. These data are combined with a tangen tial seismic reflection profile and with Russian navy refraction velocities to produce a seafloor to upper mantle velocity-depth function. The gently dipping sedimentary horizons contrast with the hummocky basement topography on the reflection profile. The seismic basement is interpreted as oceanic layer 2 consistent with the Russian navy velocities. Velocities of 6.7 km s (-1) determined for the lower crust and 8.0 km s(-1) for the upper mantle a re constrained by the seismic record sections. The 6.7 km s(-1) velocity la yer is interpreted as oceanic crust layer 3. The well-resolved thickness of this layer of 15 km is substantially greater than the average thickness fo r layer 3 of 4 km. The velocities and thickness from the Makarov Basin, oce anic plateaus and hotspots, and continental crust are summarized for compar ison. The character of seismic reflection basement and the velocity-depth f unction are consistent with thick oceanic crust in the Makarov Basin. (C) 1 999 Elsevier Science B.V. All rights reserved.