District 590 is divided into two Units on the basis of morphology:
591 Margaree Plateau
592 St. Lawrence Slopes
District 590 is underlain by resistant early Carboniferous strata that flank the Highlands Region in Cape Breton. The rocks are predominantly coarse early Horton deposits, but in many places along the western side of the Highlands, Early Carboniferous lava flows are found; some reach 300 m in thickness.
These Early Carboniferous deposits are in some places in fault contact
with the Highlands Region and in others have been deposited directly onto the surface. Immediately at the contact, the Carboniferous strata are often tilted up or domed, indicating that the highland block moved up vertically through them. In some places away from the contact, domed hills of Early Carboniferous strata occur. These domed hills may conceal blocks of the ancient rocks underneath them. Examples of these hills are Hunters Mountain and Salt Mountain. Elsewhere, these resistant strata form shoulders high on the slopes of the Highlands. The Highlands may once have been covered by many thousands of feet of Carboniferous rocks, which have been stripped away, leaving these resistant remnants. Occasionally pockets of Middle Carboniferous strata remain, such as those of the Riversdale Group around Chimney Corner, but these have generally been preserved in downfaulted blocks. Similarly, the Windsor strata that are found here and there around the margins of the Highlands lie almost entirely in faulted valleys.
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The District is dissected by faults which lie predominantly northeast to southwest, parallel to the fold direction typical of the Carboniferous Basin, and parallel to the general structural trend in Cape Breton. These faults are usually followed by river valleys. The terrain is generally elevated and rugged, reaching 300-350 m in places along the slopes of the Highlands.
The District is heavily mantled with glacial deposits that were washed down during deglaciation of the Highlands. These are thickest close to the Highlands slopes, particularly where the ice followed fault valleys, such as those of the Margaree and Middle rivers.
A wave-cut notch 6-10 m above the high tide mark is prominent around Cape St. Lawrence from Chéticamp to Cape North and beyond to Cape Smokey. In places it is overlain by peat of early Wisconsinan age.
Because much of this plateau flanks the Highlands Region and is deeply dissected, there is considerable relative relief, with many fine views from the valley floors. Indeed, a considerable stretch of the scenic Cabot Trail traverses Unit 591, following the broad valleys of the Middle River and the Margaree River system. Other valleys of high scenic quality have been cut by the Baddeck and North rivers. In all cases, the flat river valley floors are enhanced by livestock farms and contain ocean inlets at their mouths. The northern areas (sub-Units 592b and 592c) exhibit fine coastal scenery.
|T2.1 Introduction to the Geological History of Nova Scotia|
|T3.3 Glaciation, Deglaciation, and Sea-levelChanges||