The Jurassic faunas of the Canadian Arctic, Lower Jurassic Ammonites, biostratigraphy and correlations

Abstract

A number of ammonite genera and species previously unknown in the Lower Jurassic beds of the Cana di an Arc tic are described in this report. These are: Psiloceratinae? (possibly Hettangian), Charmasseiceras and Coroniceras (Primarietites) (Bucklandi Zone of the Lower Sinemurian), Gleviceras plauchuti Frebold sp. nov. (Oxynotum Zone of the Upper Sinemurian), Echioceras ak/avikense Frebold sp. nov. and Echioceras arcticm Frebold sp. nov. (Raricoslatum Zone of the Upper Sinemurian), Amalrhem stokesi ( J. Sowe rby) (Margaritalus Zone of the Upper Pliensbachian), Hi/daires sp. indet. (Falcifer Subzone of the Lower Toarcian), and Zugodacrylites cf. braunianus (d'Orbigny) (Braunianus Subzone of the Middle Toarcian). The generic posit ion of some previously described ammonites is revised: the Late Toarcian species Peronoceras spinatum (Frebo ld) and P. po/are (Frebold) were assigned formerly to Catacoeloceras Buckman. The sequence of Lower Jurassic ammonites in the Canadian Arctic Archipelago is now more complete. Moreover, it is virtually identical to that in the Richardson and British Mountains and in northern Alaska. In addition, the principal gaps in the sequences of the three compared areas (Lower Pliensbachian and upper part of Upper Toarcian) are the same. There are also close similarities to the sequence in northeastern Russia.