Crustal structure of the outer Voring Plateau, offshore Norway, from oceanbottom seismic and gravity data

Four ocean bottom seismograph (OBS) profiles acquired across the continent- ocean transition zone of the outer Voring Plateau have been modeled by inve rsion and forward modeling of the OBS vertical component traces (P waves). The thickness of the sedimentary layers deposited since the early Eocene co ntinental breakup varies from up to 2.2 km above the basaltic inner flows ( IF) to a minimum of 0.2 km about 20 km seaward of the Voring Escarpment (VE ), with a velocity of 1.6-2.55 km/s. The thickness of the uppermost layer o f basalt varies from 0.5 to 4.5 km, and its velocity ranges from 3.4 to 5 k m/s. The modeling of the two dip profiles suggests that strongly intruded p reopening sedimentary rocks extend similar to 40 km seaward of the VE. Fart her seaward, another layer of extrusives/intrusives is found beneath the up permost layer of basalt. The lateral variations in velocity in the main cru stal layer along the dip profiles indicate that the continent/ocean transit ion extends over a 30-50 km wide zone in between (strike) profile 3 (oceani c; 6.6-7.35 km/s) and (strike) profile 4 (continental; 6.1-7.0 km/s). An up to 7 km thick lower crustal high-velocity body (7.1-7.4 km/s) is interpret ed in terms of intrusions in the lower crust beneath and landward of the co ntinent/ocean transition. The total thickness of the normal oceanic crust i s estimated to be 7-9 km, the anomalously thick oceanic crust reaches a max imum thickness of about 25 km, and the crustal thickness is estimated to be 17-22 km beneath the IF. Gravity modeling of the profiles confirmed all ma in aspects of the velocity models and provided constraints on the crustal s tructures toward the ends of the profiles where the ray coverage was low.