Hettangian (Lower Jurassic) rocks and faunas, northern Yukon Territory

Abstract

The Lower Jurassic Hettangian Stage is documented with certainty for the first time in the Canadian Arctic. It is represented by a basal Jurassic sandstone unit in the Bonnet Lake area of northern Yukon Territory. The two subzones of the Early Hettangian Planorbis Zone, i.e., the Planorbis Subzone and the Johnstoni Subzone, are indicated by poorly preserved Psiloceras sp. indet. and Psiloceras (Caloceras) cf. P. (C.) johnstoni (J. de C. Sowerby), respectively. The varied but poorly preserved bivalve fauna associated with P. (C.) cf. P. (C.) johnstoni includes Prosogyrotrigonia (?) sp. cf. P. inouyei (Yehara), Cardinia sp. cf. C. hybrida (J. Sowerby), C. sp. aff. C. concinna (J. Sowerby), Pleuromya (?) sp., Meleagrinella (?) sp., Oxytoma (Oxytoma) sp., and Parallelodon (?) sp. The bivalves closely resemble approximately coeval forms described from Japan. The above-mentioned faunas are figured as is a specimen of Psiloceras cf. P. erugatum (Phillips), which was previously described from the Hettangian of southern Yukon. Other occurrences of the Hettangian in Canada and Alaska are reviewed.