Multichannel Seismic Investigation of Velocity Structure of Megamullions on the Mid-Atlantic Ridge

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

OCE 99-87004 Tucholke Award is for a multichannel seismic (MCS) reflection survey of three well-developed structural exposures of deep-crustal plutonic and upper-mantle ultramafic rock that occur on the flanks of the Mid-Atlantic Ridge. These smoothly-domed, "turtleback" shaped exposures, termed megamullions, apparently represent detachment fault surfaces associated with extensional processes at the nearby spreading ridge, and are characterized by extensive and prominent corrugations (mullion structures). These MCS surveys should establish the upper seismic velocity structure of these megamullions both laterally and vertically, and will give insight both into the deep nature of the oceanic crust and upper mantle now exposed in these megamullions as well as give a better understanding of how and why megamullions form. This survey would also serve as a foundational site survey to Ocean Drilling Program (ODP) proposals 512-Full and 532-Full and addresses several crustal objectives of the ODP Long Range Plan. ***