GEOLOGICAL MAPPING IN THE CORDILLERA - THEN AND NOW

J.O. Wheeler
Geological Survey of Canada, Vancouver, B.C. 
 
In 1945, less than a quarter of the Canadian Cordillera had been mapped at 1:250 000 (4 miles to 1 inch) or on larger scales by the Geological Survey of Canada and the British Columbia Mineralogical Branch. After 1945 the Geological Survey of Canada accelerated its mapping to begin the golden age of Cordilleran surveys which ended with the completion of the primary 1:250 000-scale coverage in 1978.

Until the mid-1950s Geological Survey of Canada mapping was done largely by six-man parties using pack horses (Figures 39 and 40), canoes and backpacking (Figures 41 and 42) methods, without radios, serviced in remote areas by fixed-wing aircraft. Topographic maps were inadequate but air photos were gradually becoming available. It took about five years to complete a 1° by 2° quadrangle.

 

Figure 39. Packing the stove-horse in the Selwyn Mountains, Yukon Territory, 1952.	Figure 40. Packhorse down in beaver slough, 1952, Macmillan River, Yukon Territory.

 

Figure 41. Geological Survey of Canada field crew backpacking in the Kluane Range, Yukon Territory, in 1954.	Figure 42. Geological Survey of Canada field party fording a glacial stream in the St. Elias Mountains in 1955.

By the late 1950s piston helicopters were used for geological fieldwork (Figure 43). For efficient operations field parties used radios and were enlarged to include various specialists. The helicopter set out traverse teams, serviced fly camps (Figure 44) and served as a vehicle for geological mapping and revisiting critical localities. The rate of geological surveying increased to two quadrangles per year in Yukon and one every two years in the southern Cordillera. By this time more accurate topographic maps and better snow-free air photos were available.

 

In the 1970s the advent of faster, larger and costlier helicopters, though they increased the range of operations, required larger parties and a large slice of the Geological Survey of Canada field budget for efficient usage.

 

By the 1980s the present revision mapping was well under way. This requires selective geological surveys of significant and problem areas at 1:50 000 scale and less detailed coverage elsewhere. The slower pace of the work, in which a 1° by 2° quadrangle is revised in three to four years, coupled with higher helicopter charges and declining field budgets, has led to further logistical changes. Geological Survey of Canada parties, which now include women, have now returned to more old fashioned methods such as fly camping and backpacking, supplemented by judicious use of helicopters.

 

Figure 43. Setting food caches by helicopter for a Geological Survey of Canada camp in the Selkirk Mountains, 1961.	Figure 44. 1961 Geological Survey of Canada field camp at timberline in the Selkirk Mountains.