Aerial Photographic Interpretation of Precambrian Structures North of Lake Athabasca

The objective of this study has been to determine the type and pattern of structures found on the Precambrian Shield of northeastern Alberta.

The work was undertaken in order to make available more geological information on this part of the Canadian Shield which, on the basis of proven mineralization under similar geological conditions, should be of some interest with regard to its mineral potential. As mineralization in Shield materials is quite commonly associated with faulted structures, it is hoped that this study - which shows lineal and structural features of northeastern Alberta - will be an aid to prospecting. The study was made from some 700 aerial photographs on a scale of 1:40,000, obtained from the Technical Division, Alberta Department of Lands and Forests, Edmonton.

As a consequence of the large area studied, approximately 3,600 sq. miles, much of the finer structural detail, has been omitted on the final map presentation. Generally, only the coarse physiographic features have been selected for inclusion except where it was thought that the smaller features were of significance in the interpretation and understanding of the larger structures.

Unfortunately, interpretations are not always clear and decisive. For example, the topographic expressions of faults of similar magnitude in massive granite, granite interlensed with softer met sediments, and met sediments alone, are completely different. In general, massive granite exhibits a relatively high relief due to its weather-resisting qualities, and faults within the granite are evident as prominent fractures and scarps. On the other hand, faults in a belt of met sediments may have little or no topographic expression, and may be covered entirely by muskeg.

Some evaluation of this and other problems has been possible by means of a quick reconnaissance and spot check over the area, and some detailed geological mapping has been carried out in the Andrew Lake district.