ABSTRACT

Two facies provinces are present within the Devonian Fairholme group, one predominantly of carbonates and one predominantly argillaceous. The term Flume is redefined to contain only the widespread, mappable, cherty biostromal carbonate unit formerly called 'lower member of the Flume formation' (deWit and McLaren, 1950). The argillaceous limestone unit, formerly called 'upper member of the Flume formation' (deWit and McLaren, 1950) is named the Maligne formation. The Flume (re-defined) is correlated with the upper part of the Beaverhill Lake formation and is of latest Middle Devonian age. The Maligne formation is correlated with the Cooking Lake formation, probably being the time equivalent of only the lower part of the Cooking Lake at its type locality, and is of earliest Late Devonian age. The Flume-Maligne boundary is one of the most important in the Devonian of the Rocky Mountains. In the interval top Alexo to top Flume the rocks may be subdivided into the Winterburn group and Woodbend group both in the surface and in the subsurface. The Nisku has been recognized in the Mountains and is grouped with the Alexo formation in the Winterburn. The rock sequence in the interval base Nisku to top Flume in the carbonate facies is the lithic analogue of and is homotaxial with the Leduc formation in the subsurface, and is therefore named Leduc. Standard surface sections of the Leduc and the Nisku formations are described from an easily accessible mountain outcorp. Within the shaly provinces in the Mountains the following formations typically are present above the Flume and beneath the Alexo (in descending order): Nisku, Mount Hawk, Perdix, and Maligne. The Mount Hawk is redefined at its top to exclude the upper carbonate member, which is included with the Nisku formation.