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MASSON, DOUG and BRIAN BETT, Southampton Oceanography Centre, Southampton S014 3ZH, UK

Abstract: Atlantic Margin Environmental Surveys

The Atlantic Margin Environmental Surveys (AMES) were carried out by the Southampton Oceanography Centre on behalf of the AtIantic Frontiers Environmental Network. Each survey was carried out in two stages: a) Sidescan sonar mapping, and b) Direct seabed investigation by coring and photography.

Sedimentary processes. Sidescan sonar images and high resolution profiles from the continental slope northwest of the UK give new insights into the sedimentary processes controlling slope morphology and depositional patterns. Data collected during AMES 1996 and 1998 are presented, including iceberg ploughmarks, channels, sediment slides, sand- and mudwaves, erosional furrows and grooves, pockmarks and sandy contourites. Summary interpretations of selected areas show how the various processes interact to form the seabed as it appears today.

Biological processes. Highlights from the surveys are presented, including: temperature variation on the west Shetland slope and its influence on faunal distributions; observations on the impact of deep-water trawling; the mass deposition of phytodetritus at some deep-water sites; and the occurrence of giant protozoans (Xenophyophorea).

Linking sidescan sonar and biological observations. Sidescan sonar and profile data show seafloor mounds up to 5 m in height and several tens of metres in diameter covering an area of around 50 sq km in the northern Rockall Trough. Many of the mounds have moderate backscatter 'tails' on their downcurrent sides. Seafloor photography shows that the mounds and tails are each associated with a distinctive fauna.The coral Lophelia appears to characterise the mounds, while the tails appear to be dominated by fields of xenophyophores.

AAPG Search and Discovery Article #[email protected] International Conference and Exhibition, Birmingham, England