HR: 14:00h
AN: OS33A-03    [Abstracts]
TI: Development of Flaser and Lenticular Bedding in Response to Tropical Cyclones
AU: * Richardson, M D
EM: Mike.Richardson@nrlssc.navy.mil
AF: Naval Research Laboratory, Seafloor Sciences Branch, Stennis Space Center, MS 39529 United States
AU: Briggs, K B
EM: kbriggs@nrlssc.navy.mil
AF: Naval Research Laboratory, Seafloor Sciences Branch, Stennis Space Center, MS 39529 United States
AB: Flaser and lenticular deposits (sensu Reineck and Wunderlich) are common in the sedimentary record and generally found associated with rippled seafloors in tidally influenced coastal waters. These features are thought to be created by deposition of suspended fine-grained mud onto a rippled sandy seafloor during quiescent periods, followed by migration of sand ripples during periods of strong tidal currents. The size of these mud deposits range from small lenses the size of ripple wavelengths (flasers) to large interconnected mud beds containing sand deposits (lenticular deposits). The development of flaser and lenticular bedding was observed on a mostly sandy shelf (5-20 m water depths) in the northeastern Gulf of Mexico after the passage of Hurricane Ivan and subsequent tropical storms. The mud was probably derived from backwash from lagoonal areas behind barrier islands after the passage of Hurricane Ivan (16 September 2004) and the mobilization of sand ripples was a result of storms. Suspended mud was deposited over the rippled seafloor during a period of relative calm. Subsequent storms Hurricane Jeanne (26 September) and, later, Tropical Storm Matthew (8-10 October) mobilized sediments creating 50-100 cm wavelength sand ripples that migrated over the freshly deposited mud layers creating buried features ranging from small, isolated flaser deposits to lenticular deposits within mud to mud deposits covering 100's of square meters. Mud deposit thicknesses ranged from 2 cm to as much as 15-20 cm. The temporal persistence of these features is unknown but similar flaser and lenticular bedding has been observed in chirp sonar records and sediment vibra-core samples from sediment depths below that conceivably mobilized by Hurricanes.
DE: 3022 Marine sediments--processes and transport
DE: 4219 Continental shelf processes
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly