Simon A.J. Pattison¹

(1) Brandon University, Brandon, MB

ABSTRACT: Facies Cyclicity and High Resolution Sequence Stratigraphy of the Tilston Beds (Mission Canyon Formation), SW Manitoba, Canada

The oil-bearing Mississippian Mission Canyon-1 (MC-1) Member of southwestern Manitoba consists of a stack of shallowing-upward facies successions that were deposited on a low relief carbonate platform along the northeastern margin of the Williston Basin. In the Tilston Field area, the MC-1 Member is unconformably overlain by the Jurassic Lower Amaranth Formation red beds and conformably underlain by the Mississippian Lodgepole Formation carbonates. The upper 30 m of the underlying Lodgepole Formation consists of a retrogradational stack of four shallowing-upward parasequences that vary in thickness from 5 to 12 m. These parasequences become significantly thinner upwards. The upper part of the Lodgepole records a step-wise transgression of the Mississippian sea and is interpreted as a fourth-order transgressive systems tract. A maximum flooding surface caps the top of the Lodgepole.

The MC-1 Member is subdivided into six 4 to 8 m thick shallowing-upward parasequences that pass from lime-dolomitic mudstones with interbedded packstones at the base into lime-dolomitic massive peloidal wackestones interbedded with massive to bedded peloidal-crinoidal packstones at the top. Many of the packstone beds are sharp-based, normally-graded and hummocky cross stratified, and are interpreted as storm deposits. The parasequences stack to form an aggradational to progradational parasequence set which records the progressive retreat of the Mississippian sea from the northeastern part of the Williston Basin. Each parasequence is separated by a 0.3 to 2.0 m thick shaley, lime-dolomitic mudstone or wackestone, which compartmentalize the three Tilston Field oil pools. The MC-1 Member is interpreted as a fourth-order highstand systems tract which is capped by the basin-wide pre-Mesozoic angular unconformity.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado