East-wed seismic reflection lines obtained at 14-km intervals on the eastern flank of the Reykjanes Ridge reveal patterns of sediment cover controlled by the reaction of bottom- water movement to crustal topography. Bot-tom currents have piled sediment into'drifts 3? a variety of scales. The largest of these is Gardar Drift, vyhich is constructed along fragmented basement ridge roughly 42 m.y. iril age. Basement peaks with scoured and moated sedimentary envelopes, outcropping sedimentary strata, and dune topography indicate prej valent erosion and redeposition of bottom sediments. No conformable pelagic draping is anywhere visible in the surveyed vea. Two prominent sediment reflectors occur on crust as young as 17 m.yjand 37 m.y., which sets a maximum limit qp their ages. The younger reflector is highly variable in apparent reflectivity; it is well developed in fracture zones but is indistinct or absent on high-standing crustal blocks of equivalent age between fracture zones. The basement expression of these fracture zones is 12 to 45 m.y. in age ami has been virtually smothered'-by the thickest sediment cover (1.75 km) observed in the survey area.. Part of the fracture zone Ailing appears to be sediment redistributed by bottom currents, but the increased sediment smoothness and re-flectivity in the fractures suggest localized turbid downslope flow within the ridge flank.
In the last 5 to 10 m.y., coarse basaltic sand mainly from Iceland (at 64° N.) has been spread across a broad trough-contained fan southwest of the Iceland-Faeroes Ridge. At 58° N., the turbidite flow is funneled into Maury Channel, ultimately to be spread out onto the Biscay Abyssal Plain at and below 48° N., 1,600 km to the south.
Figures & Tables
Edited by Peter A. Roma and published in 1976, Mid-Atlantic Ridge contains a collection of related articles reprinted from other Geological Society of America publications as well as a brief review of exploration of the Mid-Atlantic Ridge from 1960 to 1975.