Psammichnites gigas from the lower Cambrian of the Mackenzie Mountains, northwest Canada, and their biostratigraphic implications

Abstract New occurrences of Psammichnites gigas are reported from the Mackenzie Mountains, northwest Canada. A locality in the hanging wall of the Plateau Fault, just below the top of the upper member of the Backbone Ranges Formation, demonstrates that the uppermost part of the unit is Tommotian (latter part of Cambrian Age 2) or possibly earliest Atabanian (earliest Cambrian Age 3) in its previously undated proximal manifestation. Localities in the trilobite-bearing Sekwi Formation confirm that Psammichnites gigas can be at least as young as Atdabanian (early to middle parts of Cambrian Age 3) in Laurentia. A review of reported occurrences suggests Psammichnites gigas, and the related ichnotaxa Plagiogmus arcuatus and Taphrelminthopsis circularis, may be valuable for correlations in western Laurentia if their ichnotaxonomic relationships are clarified.