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Chapter 13: Mining and Oil Extraction

13.5: Sand/Gravel Pit on the Assiniboine Delta

The Assiniboine Delta deposited into the west side of glacial Lake Agassiz is a massive accumulation of sand and gravel.[i] Coarse gravel near the apex east of Brandon gradually gives way to sand further east. The present-day Assiniboine River has etched a steep-sided meandering valley into the sands as it adjusted to a new base level with the retreat of Lake Agassiz. Here are two meander loops of the eastward-flowing Assiniboine River 1 eroded into sands which are exploited at a large pit 2 with two smaller ones to the north 3. In the large pit excavation has reached the water table resulting in flooding (dark-tone) of the bottom 4.

Other points to note on this photo are a) PTH 34 5 between Holland (to the south) and Austin (to the north) is cut into the sands of the delta 6; b) delta sands have been blown into dunes north of the river 7; these are now stabilized by a mixture of grasses (light-toned) 8, deciduous woodland (dark-toned) 9 and coniferous trees (identified by their triangular shadow) 10; c) the south side (north-facing side) of the Assiniboine Valley is heavily wooded by deciduous trees (dark-toned with rounded crowns) 11; d) fields that have been cleared for agriculture are medium-dark toned 12, indicating that the crops in them are still green and that the date of the photo is pre-harvest; and e) one field is in the process of being cultivated 13; the cultivated part of the field is darker-toned 14, and by using a magnifying glass with the original photo, the machine doing the cultivating can be seen 15.

Figure 13.5: Sand/Gravel Pit on the Assiniboine Delta

Figure 13.5: Sand/Gravel Pit on the Assiniboine Delta

Figure 13.5

Vertical air photograph: A16574-87

Flight height: 9000 feet; lens focal length: 6 inches

Scale: 1:16,000 (approx.)

Date: June 19, 1959

Location: Township 8 and 9; Range 11WI

Map sheets: 1:250,000 62G Brandon

                    1:50,000 62G/11 Treherne


[i] For a map of the location of the Assiniboine Delta see Corkery M. T. “Geology and Landforms of Manitoba” in Welsted, Everitt and Stadel op. cit.. 1996, figure 2.4, 18.