Marvin Spur - Lomonosov Ridge Relationships Based on Reflection Seismic Profiling Near the North Pole

Reflection seismic profiles acquired from the drifting ice-station NP-28 in 1988-1989 and other neighboring profiles provide evidence of the character and origin of the Marvin Spur and Lomonosov Ridge. The NP-28 seismic images of the sedimentary successions capping the Ridge can be correlated with those of the AWI- 91090 profile, which was calibrated by the ACEX drilling at 88º N. Along the AWI line, the most prominent reflector package marks the base of the Cenozoic (Paleocene) section and its angular unconformity to underlying Mesozoic strata. The NP-28 ice-station crossed the Lomonosov Ridge three times, near the North Pole. In each profile, the Marvin Spur is also imaged, in one case below the floor of the Makarov Basin and in the two others as a narrow ridge parallel to the Lomonosov Ridge. A prominent composite reflector occurs at a few hundred meters depth in the sedimentary successions on both the Lomonosov Ridge and the Marvin Spur, underlain disconformably by less regular reflectors, dipping towards the Amerasian Basin. Correlation of both the seismic images and velocities (Vp) with the AWI-91090 profile suggests that this composite NP-28 reflector marks the base of the Cenozoic. The reflection profiles across the Lomonosov Ridge and Marvin Spur are similar; probably the Spur is a narrow sliver of thinned continental crust that was rifted off the Ridge. Towards the Greenland margin, the trough between the Lomonosov Ridge and the Marvin Spur narrows and the two appear to merge. Towards the Siberian margin, the trough widens and the crest of the Marvin Spur sinks beneath the Makarov Basin. It has been also imaged further along strike beneath this basin in the TRA(b)-90 profile (Langinen et al, ICAM-IV in press), where the composite reflector marks a clear unconformity capping the Spur and adjacent older successions. These lines of seismic evidence need to be tested by piston coring and drilling. They emphasize the importance of Cenozoic faulting for controlling the central Arctic bathymetry and the complexity of the boundary zone between the Lomonosov Ridge and the Amerasian Basin. Thinned continental crust is probably present even beneath parts of the Makarov Basin.