Unit 582 is divided into two sub-Units:
(a) Pictou Rivers
(b) McArras Brook
Geology and Landscape Development
This hilly area between the Cobequid Hills and the Pictou-Antigonish Highlands is underlain by Late Carboniferous Canso and Pictou strata, which are interrupted on the southeastern margin by triangular upfaulted blocks of Windsor strata. A separate part of this Unit (sub-Unit 582b) lies east of central Pictou between McArras Brook and Doctors Brook.
The Windsor Group strata are predominantly composed of sandstone and siltstone with minor amounts of gypsum and anhydrite. The landscape reflects the dominance of these relatively more-resistant rocks, and although it is well dissected by streams, elevations exceed 200 m in places and reach 225 m at Hopewell and Lorne.
Part of the East River north of Sunnybrae is a fossil valley that became filled with Windsor deposits and is now being re-exposed. In the central part of the Unit is the Pictou coalfield. The basin in which the coalfield sits developed as a physiographic feature during the Acadian Orogeny when it was downfaulted. Since then it has acted as a sedimentary sink, and during the Late Carboniferous it provided a suitable environment for the development of coal seams.
The coalfield underlies an area about 5 km by 16 km beneath New Glasgow, Stellarton, and Trenton. The coal seams lie in grey shales, which are open folds dipping to the east. The total thickness of the coalfield is about 2,600 m and bears up to 45 seams, 11 of which have been mined. The coal seams were formed in a tectonically unstable area in which periods of quiet plant growth were separated by subsidence and inundation by muds. The seams, therefore, grade vertically and laterally into shaly coal and coaly shale.
Most of the Pictou Rivers sub-Unit (582a) falls within three tertiary watersheds, draining the East River, Middle River, and West River north into Pictou Harbour (see Figure 19). Drainage patterns are rectangular, and surface water is slightly acidic to neutral. Extensive floodplains occur along the East River in sub-Unit 582a.
|Some brooks erode fossils from rocky banks
Click to enlarge
The soils in this Unit have been derived from shales and sandstones.
Pictou Rivers (sub-Unit 582a)
Well-drained Woodbourne soils (gravelly clay loams) are found associated with imperfectly drained Millbrook clay loams, with small amounts of gravelly Hebert soils formed on glaciofluvial deposits. Clay soils of the Queens and Joggins series are found around Stellarton.
McArras Brook (sub-Unit 582b)
Woodbourne soils also occur together with Barney soils south of Arisaig (well-drained shaly loams).
White Spruce and Balsam Fir grow on old fields and pastures. Sugar Maple, Yellow Birch, and American Beech grow on slopes, with shade-intolerant birches, Red Maple and aspen. Some remnants of intervale old growth forest remain along the West Branch of the East River of Pictou.
The East, Middle and West Rivers support significant salmonid habitat.
Soils in this Unit are productive,
and much of the area is farmed. For the Scottish settlers coming to this area in the late 1700s, the Pictou Valleys provided reasonably good farmlands once the trees were cleared. Forestry exploitation in this area was very extensive in the 1800s, supplying timber exports to Britain. The forestry industry continues to be important here, as is mining around the Pictou Rivers (sub-Unit 582a).
|River near Arisaig, Antigonish County
Click to enlarge
Coal was discovered in the Pictou coalfield in 1798 on McCullochs Brook and was worked in the early 1800s; mining continued sporadically into the 1900s, with most operations ceasing by 1960. The three main coal-producing districts are Thorburn, Albion, and Westville. Most recently, coal mining took place at Westville. The coal from these mines was a major factor in the industrial development of this area. At McArras Brook (sub-Unit 582b) the economies of small communities are based on fishing, farming, and lumbering. Arisaig has a prosperous fishery.
Sites of Special Interest
- Arisaig (sub-Unit 582b) - a 5-km-long section of the shoreline has the best continuous exposure of Silurian and Devonian sediments in North America; a wide variety of tropical marine fossils occurs, including graptolites, brachiopods, bryozoa, trilobites, crinoids, and cephalopods
- Hopewell - intervale forest with rare plants
Provincial Parks and Park Reserves
- Salt Springs
- Green Hill
- Guysborough Railway (part)
Proposed Parks and Protected Areas System includes Natural Landscape 42.
|T2.1 Introduction to the Geological History of Nova Scotia|
|T2.4 The Carboniferous Basin|
|T8.1 Freshwater Hydrology|
|T10.1 Vegetation Change|
|T12.3 Geology and Resources|
|T12.10 Plants and Resources|
|H6.1 Hardwood Forest (Sugar Maple, Yellow Birch, Beech Association)|
|Associated Offshore Unit
|Sub-Unit 582b: 914 Northumberland Strait sub-Unit |