ABSTRACT
Stratigraphic and structural relations within the late Paleogene Kishenehn Formation demonstrate that there are neither profound angular structural divergences within, nor significant truncations of, the strata. There is therefore no need to postulate the existence of unconformities of greater rank than that of a diastem. Subtle structural discordance and local truncations visible at the locality where MacKenzie (1916) reported an angular unconformity are readily explained in terms of sedimentary lensing and channelling within fluviatile sedimentary rocks. Sedimentation in the asymmetric Flathead graben kept pace with the northeasterly tilting resulting from normal displacement on the listric, southwest-dipping Flathead fault zone. The history of displacements on this fault zone is recorded in the stratigraphy and structure of the Kishenehn Formation.