Geoscience Reference
In-Depth Information
Plate 12.9
Seismic data sea-bed image of the rifted Faröe-Shetland channel, some 420 km from north-west to south-east. The
image is incomplete but detail on the West Shetland shelf (lower centre) reveals glaciomarine sediments and iceberg keel marks
and, on the steep shelf-slope system across the centre right of the image, submarine gulleys, turbidite flows and fans. These are
best seen through a magnifying glass, viewing the image from the north-west corner.
Image: By permission of the British Geological Survey
gravel qsand qmud, as the respective particles settle
out over time (
Plate 12.10
).
Sediment sequences several
kilometres thick form in the slope-rise area in this way.
Abyssal plain sediments are usually isolated from
adjacent slopes in the 'quietest' parts of the ocean and
accumulate extremely slowly. They are primarily
undisturbed biogenic muds 0·5-1·0 km thick, forming at
turbidite exposed in a 130 m high rock wall by landsliding
beneath Mam Tor, Derbyshire. Each sandstone bed fines
upwards into thinner sands and shales before the cycle is
repeated.
Photo: Ken Addison
