Sedimentology of the Turbidite-Dominated Upper Paleozoic Tuttle Formation, Peel Plateau, Yukon, Canada

Tammy Allen and Tiffani Fraser
Yukon Geological Survey, Whitehorse, YT, Canada

The Upper Devonian to Lower Carboniferous Tuttle Formation forms the upper part of a prograding siliciclastic wedge that was deposited in the foreland basin of the Yukon and Ellesmerian fold belts. The Tuttle Formation, characterized by alternating coarse-grained and fine-grained clastic rocks, is of regional significance to the oil and gas industry in terms of source rock and reservoir rock potential. In the Peel Plateau region, the Tuttle Formation is also important stratigraphically as it is distinct from neighbouring units that are predominantly fine-grained marine deposits.

Outcrop exposures the Tuttle Formation consist of alternating intervals of resistant and recessive siliciclastic rocks. Resistant intervals, 20 to 55 m thick, comprise predominantly sandstone with lesser conglomerate and siltstone. Recessive intervals, 55 to 140 m thick and typically covered, are predominantly laminated siltstone and shale. The same relationship between coarse and fine intervals is noted in the subsurface on wireline logs over a thickness of up to 1250 metres. Normally graded sandstone packages are the most common lithofacies observed within the resistant intervals. They are characaterized by granule conglomerate at the base grading to fine-grained sandstone and siltstone at the top and are interpreted as partial Bouma sequences. Less common lithofacies include massive sandstone, sandy granule to pebble conglomerate, diamictite, parallel- to cross-laminated siltstone and shale.

A deep water turbidite depositional model is suggested for the Tuttle Formation based on lithofacies and observed sedimentary structures including repeated normally graded sequences, sharp to erosional based beds, tool marks and flute marks. Ongoing research is required to determine the paleogeography of the Formation and its significance to the foreland basin evolution.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas