923 Valleys and Plains
| Geology & Seabed Morphology
| Sediments | Oceanography Plants | Animals | Cultural Environment | Topics & Habitats |
Geology and Seabed Morphology
This zone occurs between depths of 100 and 200 m. It contains the intervening areas of bottom between the Middle Shelf banks and the basins. No distinctions have been made between the bedrock geology of this zone and that of the two previous Units, but this Unit contains various glacial features associated with the basin flanks, including submarine moraines and relict iceberg scours. Because of the sloping terrain, the area is probably subject to phenomena such as slumping.
Sediments
The upper levels of the basins frequently have deposits of glacial till, which also occurs in the moraines on the inner flanks of the basins. This Unit also frequently contains sands mixed with clay and silt, in contrast to the well-sorted deposits of the banks. These deposits may be flat and smooth to undulating and hummocky, and on the Scotian Shelf are called Sambro Sand.
Oceanography
Oceanographic features are as in the regional description.
Plants
This Unit occurs below the depth of seaweed growth, and phytoplankton is the principal vegetation.
Animals
Fauna in the water column reflect that in adjacent basins and banks.
Cultural Environment
These intermediate areas between the banks (Unit 921) and basins (Unit 922) are used for bottom trawling and line fishing for species such as American Plaice, Witch Flounder, and Yellowtail Flounder.
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