The Mid-Atlantic Ridge Near 45 °N. XXII. Sedimentary Deposition and Lithogenesis on Mid-Atlantic Ridge Mountain Tops

Abstract

Bottom photographs and drilled rock cores collected on several mountain tops along the crest of the Mid-Atlantic Ridge near 45°N describe the sediment distribution, sediment dynamics and shallow stratigraphy of these sites. Lag pebble deposits and pebble waves indicate rapid changes in bottom current direction and velocities that may approach 100 cm/s (>2 knots) one meter above the bottom so that surface sediments are often not indicative of sediment and rock types sampled using shallow drilling techniques. Absolute dates (14C) of coralline limestone, which underlies coarse unconsolidated sediment at most drilling sites, suggest deposition and initial lithification of these deposits during a middle Wisconsin interstadial period.