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|Title:||INCISED SHOREFACE SBDIMENTS OF THE BURNSTICK MEMBER, CARDIUM FORMATION, BRAZEAU RIVER GASFIELD, ALBERTA|
|Abstract:||<p>The Burnstick Member of the Cardium Formation to been (Turonian, Late Cretaceous) occurs in the subsurface of southern Alberta and is sandwiched between the'Hornbeck Member and the Raveri River Member. These sediments were deposited in the Alberta Foreland Basin along the eastern margin of the rising Canadian Cordillera. The Burnstick Member sediments appear deposited tens of kilometers east of the closest known paleoshoreline which presents a major problem with respect to sediment transport in an offshore environment. Two possibilities exist for the deposition of the Burnstick Member sediments including, direct emplacement into an offshore environment by storm related currents ("offshore bars") or deposition in a shoreface environment during a rapid lowering of sea level (incised shoreface deposits). Approximately 130 electrical logs and 23 cores were used to determine the sedimentology and sand body geometry of the Burnstick Member in the Brazeau River area. Well log cross sections and core cross sections show that the Burnstick Member rests on a major erosional surface (E4) that outlines a sigmoidal step which is open towards the northeast. The steps are between 4-6 m deep and are int.erpreted to have developed in shoreface environments. In off-fields areas the E4 surface merges with the T4 surface (Burnstick- Raven River Member contact) and forms the E4/T4 surface. The E4/T4 surface is flat relative to a horizontal lower marker. The Hornbeck Member sedimerits, which under I ie the Burnstick Member, is composed of bioturbated shallow marine mudstones. The Burnstick Member is composed of a coarsening upward sequence which passes from bioturbated muddy siltstones up into clean conglomeratic sandstones. The Burnstick reaches a maximum thickness of 8 metres. The Raven River Member overlying the Burnstick is composed of massive black mudstone referred to as the "Black Blanket". The Burnstick Member sediments are concentrated in long, linear sand bodies, which strike NW-SE. The sand bodies rest on the incised step in the E4 surface. They are interpreted to be incised shoreface deposits that were localized on the shelf during sea level fluctuations. A rapid fall In relative sea level is proposed to have initiated lowstand shoreface development on the shelf. stillstand caused the shoreface to retreat towards the southwest and become incised into the underlying Hornbeck Member. A transgression is proposed to have followed, which planed off the upper shoreface and evidence of subaerial erosion to the southwest. This transgression eventually buried the Burnstick Member sediments in marine muds.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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