Provenance and depositional framework of braided and meandering gravel-bed river deposits and associated coal deposits in active intermontane piggyback basins: The Upper Jurassic to Lower Cretaceous Tantalus Formation, Yukon

The Tantalus Formation developed within confined intermontane river valleys during the late stages of collision and amalgamation of Stikinia and associated arc systems with the North American plate in Upper Jurassic and early Lower Cretaceous times. While most of the extensive chert pebble conglomerate in the Tantalus Formation can be interpreted as shallow braided gravel-bed river deposits, some may represent the products of deposition from deeper, braided and meandering gravel-bed rivers. Floodplain and lake deposits are restricted to poorly exposed slope forming intervals. Coal deposits developed locally on abandoned segments of floodplains in confined river valleys, in places associated with high constructive river deposits. The age profiles of detrital zircons indicate major contributions from reworking of older strata, combined with continued un-roofing of the Stikine terrane. In addition more distal sources were tapped in the Yukon-Tanana and adjacent terranes to the north and west of the Whitehorse trough. Much of the chert in the Tantalus Formation appears petrographically similar to chert in the Cache Creek terrane, now preserved only to the south of the Whitehorse…

Publisher

Government of Yukon

Resources

5

Catalogue metadata updated

2026-08-26