Physical Geography of the Brokenhead Beausejour Area - By Ron Jackson
A complete understanding of the history of an area involves not only a study of human settlement but also a study of the natural history in order that settlement patterns and the evolution of present land use can be more readily understood. It is the intent of this chapter to give the reader an understanding of the formation of the landforms within the Beausejour-Brokenhead area and, in a small way, perhaps, to impart an image of what type of vegetation the first settlers were faced with when they arrived in this area.
1. Bedrock Geology:
The bedrock geology within the BeausejourBrokenhead area consists of rock originally formed between four billion and 230 million years ago. In the northeastern part of the R.M. of Brokenhead are some rock outcrops traditionally referred to as the Precambrian Shield. This rock was formed during the Precambrian Era between four billion and 600 million years ago and may be the first rock formed when the earth was created.
To the west, in the Garson area, one can see the bedrock comfIlonly referred to as Tyndall stone (dolomite). This sedimentary rock was formed from a large inland sea complete with many species of corat snails and other marine life. If one examines this work closely it is possible to see "fossils" of some of this marine life. As one proceeds east from Garson the Tyndall stone is found at greater depth until a north-south line approximately along Highways 302 and 12 where the dolomite stops at approximately 100 feet in depth.
East of this line is sandstone which was formed prior to the Tyndall stone.
2. Surficial Geology:
Surface Relief and Soils The event which perhaps had the greatest effect on the Beausejour-Brokenhead area was the Pleistocene glaciation and associated with that, Glacial Lake Agassiz. This event occurred from approximately 7,000 to 250,000 years ago.
A climatic change occurred at the beginning of this time period which resulted in temperatures becoming colder. Snow, rather than completely melting each year, gradually turned to ice in the Canadian Arctic. Over many centuries this process resulted in a mass of ice from one to three miles thick slowly moving southward across Canada. As the ice moved south, it scraped soil rock and other debris before it incorporated this material within the ice.
This massive sheet of ice finally stopped in the northern United States when approximately 225,000 years ago a warmer climate change occurred. With the warmer climate, the ice sheet began melting, causing it to retreat northward leaving behind the accumulated rock and soil called "till". Since the Beausejour-Brokenhead area drained northward, the ice sheet now to the north, acted as an effective dam causing the meltwater to build up south of the ice un til it found a drainage route to the south down the Mississippi River System. The resulting lake, which existed from 7,000 to 12,000 years ago, is referred to as Glacial Lake Agassiz. It is estimated that the Beausejour-Brokenhead area was under several hundred feet of water at this time.
While covered with water much of the silts and clays which constitute the texture of the local soils were deposited. When the ice sheet to the north finally melted, approximately 7,000 years ago, Glacial Lake Agassiz was drained resulting in a surface relief much as we see it today. In fact Lakes Manitoba, Winnipeg and Winnipegosis are remnants of the former Glacial Lake Agassiz. The drainage of the Beausejour-Brokenhead area is generally in a northwest direction, eventually emptying into Lake Winnipeg. The elevation of the Beausejour-Brokenhead area varies from 760 feet above sea level in the northwest part to approximately 890 feet above sea level in the southeast.
The topography varies from level to gently sloping with a slope gradient of two to four feet per mile. There is a noticeable relief pattern of ridges running northwestward and southeastward. Devil Creek and the Brokenhead River are the major drainage collectors. Since there are a total of 18 different parent materials which are responsible for the soil types of the Beausejour-Brokenhead area, a complete discussion of the local soil is beyond the realm of this chapter. Therefore, only a brief overview of the areas soil types will be given. Most of the soils within the BeausejourBrokenhead area can be classed as Black Soils or Grey Wooded Soils. Black soils are characterized by a high organic content dark colours and high moisture retention. Because of these soil characteristics a wide range of agricultural activities can be supported.
"Chernozen" is another name for black soil: this is a Ukrainian and Russian word that means "black soil". Grey Wooded Soils are predominant where there originally grew a mixture of coniferous and deciduous trees. As a result of a summer water deficiency, these soils usually have an accumulation of calcium carbonate (lime) at some depth which is indicative of a podzol. In addition to the above are the peat soils found on the margin of the Lydiatt bog and to the east of the Brokenhead River. Where the soil is well drained the peat has potential for good agricultural production. However, peat acts as insulation. In the spring the peat cover retards the rate at which the soil warms, while in the fall, during frost, the peat prevents the soil warmth from mixing with the air, usually resulting in frost damage to the more tender crops.
With the current research being undertaken on peat soils in the area, better agricultural use of these soils may occur in the future.
The Beausejour-Brokenhead area climate is designated as dominantly subhumid, cool continental according to the Koppen classification. Since this area is located in the center of the continent, a great distance from the moderating effect of the oceans, the summer temperatures are higher, winter temperatures are lower and the annual temperature range much greater then the world average for the same latitude.
The BeausejourBrokenhead area receives approximately 20 inches of precipitation annually. Approximately 70% of the annual precipitation falls from April to October, while 30 to 40% of the total precipitation falls during May, June and July. The mean annual temperature for the Beausejour area is 2°C with July being the warmest month at 24.8°C and January the coldest at -24.3°C. The mean length of the growing season (frost free 3 period) varies from 117 to 119 days.
When the first settlers arrived in the Beausejour-Brokenhead area, they were confronted with a large expanse of forest. The Beausejour-Brokenhead area is located on the border of two major vegetation zones; borealforest, and aspen -oak parkland. The most common vegetation type in the area was the aspen-oak parkland. In this natural vegetation poplar was the most common tree species on the low lying soils while the ridges and better drained sites supported a mixture of bur oak and poplar.
As one travels around the Brokenhead area today, remnants of this vegetation can be seen in existing woodlots. Boreal forest vegetation consists mainly of coniferous trees such as jack pine and spruce. On well drained sites jack pine, white spruce, and in some instances, poplar and birch are the major vegetation types. In low-lying areas, black spruce and tamarac are the major vegetation types. Areas illustrating the boreal forest vegetation can be seen today in the Mars Hill area, and in the extreme southeast corner of the R.M. of Brokenhead in the Lydiatt area. The geography of the Beausejour-Brokenhead -Garson-Tyndall area is especially fascinating because it combines elements of the Canadian Shield, on the east, and of the Prairies and Parklands, on the west and northwest. This is the true geographic heartland of Canada in many respect