A thick section of Mississippian rocks is exposed west of Jackfish River in the LaBiche Range of the Mackenzie Mountains near South Nahanni River, Northwest Territories, Canada. Location is 123°59′ West Longitude, 61°06′ North Latitude.
From fossil evidence rocks of Kinderhook, Osage, Meramec, and Chester age are known to be present.
Strata with a Kinderhook fauna equivalent in age to the Banff formation are of a similar lithology to southern sections, but equivalent Rundle strata with Osage, Meramec, and Chester fossils consist of interbedded argillaceous limestone and calcareous shale overlain by a great thickness of sandstones with minor shale and coal beds. Fossil plants Stigmaria sp. and Lepidodendron sp. and coal were found in sandstones below the Meramecian Spirifer cf. pellaensis zone.
The name Mattson formation is introduced for the thick sandstone sequence of nearshore environment which overlies the typical Banff formation lithology of interbedded argillaceous limestones and shales.
Microspores from the coal of the Mattson were identified by P. A. Hacquebard of the Coal Research Branch of the Geological Survey of Canada, Sydney, Nova Scotia, and were found to indicate a Lower Carboniferous flora. Spores in the coal are unlike those found in Mississippian coal of Utah, but are very similar to those described by the Russians from the Carboniferous of the Ukraine.