The Middle Shelf District has been divided into three Units: 921
Middle Shelf Banks 922 Middle Shelf Basins 923 Valley and Plains
Geology and Seabed Morphology The Middle Shelf extends roughly
from a depth of 110 m near shore to the inner edges of the major
offshore banks (Baccaro, LaHave, Emerald, Western, Sable Island,
Banquereau, and Georges). Definition of the Middle Shelf
District is based on the physiography of the Scotian Shelf but
has been extended to include the Gulf of Maine within the same
depth ranges. It belongs to the submerged Atlantic Coastal
Plain, and its topography was determined by erosional and
tectonic processes while it was above sea level. On the Scotian
Shelf (the continental shelf south of Nova Scotia), the inner
margin of the Middle Shelf is a trough from 145-180 m deep and
40-50 km wide. Outside the trough is a zone that has three broad
basins (Roseway, LaHave, and Emerald) and contains isolated deep
banks (Roseway and Sambro) on the western end (of 80-100 m
depth), and on the east