Abstract

The stratigraphic relations in the Lower and Middle Jurassic rocks of northern Yukon and adjacent parts of Northwest Territories indicate deposition on a broad shelf trending northeast-southwest along the contemporary North American cratonic margin. Previous interpretations of a two-sided marine trough extending generally north-south across northern Yukon (i.e. Porcupine Plain - Richardson Mountains Trough) are not substantiated.

Re-examination of the stratigraphic evidence in northern Yukon and Alaska does not indicate the presence of a source-landmass in northern Alaska and northwestern Yukon (i.e. Keele-Old Crow Landmass) in Early and Middle Jurassic times. The first major supply from such a sediment source, in northern Alaska, is in the Late Jurassic. Northerly rather than southerly sources are indicated for older Jurassic rocks in northern Alaska.

Transcurrent movement in either direction on the Kaltag Fault can neither be supported nor rejected by the Jurassic record in northern Yukon. Hypotheses of counter-clockwise rotation of northern Alaska away from Arctic Canada are not supported in view of the lack of volcanism in the Jurassic and Early Cretaceous of northern Yukon, i.e. in the proposed pivotal area of rotation of such hypotheses. The boreal character of Middle Jurassic marine faunas of northern Alaska firmly allies them with those of the Canadian Arctic.