| 600 | Triassic
Lowlands |
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| 610 | Valley |
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| 620 | Tidal
Bay |
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600 Triassic Lowlands
| Characteristics
| Geology & Landscape Development
| Climate Fresh Water | Soils | Plants | Animals | Cultural Environment Topics & Habitats |
Two Districts are recognized within the Triassic Lowlands Region are:
610 Valley
620 Tidal Bay
Regional Characteristics
Soft Triassic sandstones have been eroded to form an open-ended valley. Material from the parent rock and glacial and post-glacial deposits provide a mixture of soil types. Shelter by North and South Mountains provides the most favoured climate in the province, with a growing season of 195 days. Where the valley is open to the sea at its east and west ends, the inland climate is moderated by marine influences. Natural vegetation includes Red Spruce, Eastern Hemlock, pine forests, oak and maple forests, bogs, and salt marshes (often turned to dykeland). Mud flats are rich in life and support large flocks of migratory shorebirds.
Geology and Landscape Development
The distinctive red beds that fringe the Minas Basin and Cobequid Bay, and extend underneath the Annapolis-Cornwallis Valley belong to the Triassic Lowlands. They are made up of weakly cemented and easily eroded sandstones and sandy shale overlain by glacial deposits of varying character.
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| Grand Pré dyke Click to enlarge |
The northern side of the trough is downfaulted. The master fault is probably the Cobequid Fault, but the present boundary of the Triassic deposits is the Portapique Mountain Fault. Along this northern margin the strata are more steeply inclined than those to the south and in places are even gently folded.
During the long period of erosion up to and including the Cretaceous, much of the basalt was removed. Some still remains as a protective cap on the sandstones, but to the north, east, and south, wide bands of soft sandstone became uncovered. Rapid erosion then ensued as a river system developed in the trough followed by glacial scouring and finally marine invasion. Much of the Triassic Lowlands Region is now covered by water. The largest area still above sea level is the eastern part of the Annapolis-Cornwallis Valley, which, though undergoing rapid erosion, is protected somewhat by its flanks of resistant rock: the North Mountain basalt and South Mountain granite (see Figure 25). The western end of the valley underlies St. Marys Bay. Elsewhere the Triassic deposits fringe the Minas Basin and Cobequid Bay, forming low, rapidly retreating sea cliffs fronted by wide, wave-cut platforms and mud flats.
Climate
The climate of the Triassic Lowlands is inland in character because of the shelter provided by North and South Mountains, but is modified at the Digby and the Minas Basin ends by marine influences. The main climatic features in this region are a warm early spring, hot summers with less precipitation than elsewhere, and a higher frequency of clear skies.
Winters are cold but not severe. The January mean daily temperature is -6°C, compared to -8°C in northern Nova Scotia, and -5°C in southern Nova Scotia. Mean daily temperatures rise above freezing in late March, with the warming trend moving west to east. Spring temperatures are warm, and by July the mean daily temperature is 18°C. Mean daily temperatures fall below freezing during the first week of December. The western end of the Region, under the influence of the Bay of Fundy, is slightly milder in winter and cooler in summer.
Total annual precipitation at the eastern end and extreme western end of the Region is less than 1200 mm. Towards the centre of the valley it is somewhat higher: between 1200 and 1400 mm. Snowfall is moderate, being more than 250 cm in the centre of the Region and along the north shore of Minas Basin, and decreasing westwards. The Digby area receives less than 150 cm. The snow-cover season lasts longer at the eastern end than at the western end by approximately thirty days.
Most of the Region is relatively protected by North Mountain from seasonal fog, mist, and low cloud of marine origin, making clear sunny days more frequent than in coastal areas.
This is the most favoured bioclimate in the province. The frost-free period and the growing season (145 and 195 days, respectively) are fairly long, with an accumulation of more than 2,400 growing-degree days. Summer precipitation at the eastern end of the Region is lower than elsewhere, and this, combined with the prevalence of coarse sandy soils, can lead to droughty conditions in some years. The warm temperatures and low elevations create a high potential for evapotranspiration and a mesothermal climate. Poor air drainage on the valley floor creates frost pockets.
Fresh Water
Many streams and very few lakes are found in this Region. Numerous steep and shallow second- and third-order streams drain the surrounding higher elevations. Where they reach the lowlands, productivity is relatively high. Drainage in the Region is dendritic and parallel.
Soils
The soil map reveals a complex mix of soil types in this Region. This is attributable to the variety of parent materials and to a range of glacial outwash and post-glacial marine deposition processes. The soft, red Triassic sandstones are easily eroded and have formed deep, coarse soils. Along the footslope of North Mountain the parent material often includes a mixture of basaltic rock. Along South Mountain the till is modified at the eastern end by grey and black slates and shales, and at the western end by granite. Most of the soils are well or excessively drained sands and sandy loams. Some limited areas of imperfectly drained soils have developed on finer water-deposited materials. At either end of the Annapolis Valley, and at the head of Cobequid Bay, extensive areas of salt marsh have been dyked. Small areas of organic soils are found scattered all along the valley floor and along the south shore of Minas Basin, but not along the north shore.
Plants
The Triassic Lowlands are part of Loucks' Red Spruce, Hemlock, Pine Zone in which Red Spruce and Eastern Hemlock, now heavily cut, once attained their greatest prominence. This zone is in turn divided into two forest ecoregions.
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| Field of mustard, near Great Village Click to enlarge |
The main factors influencing regional vegetation are the warm summers, well-drained soils, and extensive disturbances by cutting and fire. The remaining stands are mostly coniferous, but there were probably more deciduous trees on the valley floor before lumbering. The climate suits shade-tolerant species, but the precipitation is just high enough to give spruce and hemlock the advantage. The main species are Red Spruce, Eastern Hemlock, White Pine, Balsam Fir, with Red Oak in the western portion, and Black Spruce and Red Maple to the east. Extensive areas are cleared for agriculture, and oldfields are common, usually regenerating in White Spruce. Extensive Red and White pine stands grow on the sand plains in the centre of the Annapolis Valley, often in association with heath barrens. Dykeland and salt-marsh plant communities are found along the coast.
Animals
This Region provides a wide range of terrestrial and aquatic habitats, including productive intertidal habitats. Terrestrial habitats include a diverse mix of open land and forested areas. The fauna of this Region includes a number of more southerly and opportunistic species often associated with agricultural areas (e.g., fox and skunk). The mud flats, salt marshes, dykelands, and estuaries are important breeding and staging areas for waterfowl and migratory shorebirds such as Semipalmated Sandpiper. Together with wet meadows, the salt marshes and dykelands are among the largest areas of suitable habitat in Nova Scotia for Arctic Shrew. Typical freshwater fishes include Atlantic Salmon, Brook Trout, and Creek Chub.
Cultural Landscapes
The Triassic Lowlands attracted the first European settlement in Nova Scotia as the French were lured by fur trade with the Mi'kmaq, the exploitable fisheries, and imperial territorial claims. Acadians chose to dyke tidal marshes to create fertile farmlands rather than clear the forests. Thus the coastal landscape was dramatically transformed. The largest Acadian community was located on the higher elevations near Grand Pré, and descendants of willow trees planted by the Acadians still stand. Both Mi'kmaq and Acadians weir-fished the river tributaries of Minas Basin and hunted the abundant waterfowl. After the 1755 Acadian deportation, successive waves of immigrants settled these fertile lands, continued to use the dykelands, and cleared valley forests to create prosperous farmlands.
Tidal-powered grist mills were established at Canning and Walton, but most grist mills were powered by river waterwheels. Numerous hydroelectric generating stations now harness waterways in this area. Today, the fertile soils of the Triassic Lowlands support the most productive farms in Nova Scotia. The advent of steamships in the nineteenth century facilitated the transport of produce overseas. The Annapolis valley's apple industry thrived during this period as produce was more likely to reach Britain in marketable condition. Railways and, later, truck transport increased other apple markets. Timber cut from forests of the Triassic Lowlands supplied local shipbuilding, furniture manufacturers, and export markets. In these primarily agricultural lands, forestry exploitation has always been economically important, and today, as in the past, many sawmills operate. Nova Scotia's first tourism ventures took place in the Annapolis Valley, attracting American tourists to the land of Longfellow's fictional quot;Evangeline" and her Grand Pré home. Today the Triassic Lowlands support many tourism and recreational activities, including bird-watching along the Fundy shores, where migrating flocks may be seen.
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