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Fluvial to Estuarine Valley-Fill Models Without Age-Equivalent Sandy Shoreline Deposits, Based on the Clearwater Formation (Cretaceous) at Cold Lake, Alberta, Canada

By
Howard R. Feldman
Howard R. Feldman
ExxonMobil Exploration Co., Room 866, 233 Benmar, Houston, Texas 77060, U.S.A. e-mail: howard.r.feldman@exxonmobil.com
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G. Glen McCrimmon
G. Glen McCrimmon
Imperial Oil Resources Limited, P.O. Box 2480, Stn. M, Calgary, Alberta, T2P 3M9, Canada
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Tim A. De Freitas
Tim A. De Freitas
Manitok Exploration Inc., Suite 2150, 736-6th Ave SW, Calgary, Alberta, T2P 3T7, Canada e-mail: Tim@Manitok.com
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Published:
January 01, 2008

Abstract

A commonly assumed element of sequence stratigraphic theory is that incised valleys must feed lowstand deltas. This model persists despite examples in which no lowstand deposit is present at the distal ends of some ancient and recent valley fills. The Clearwater Formation at Cold Lake Field, Alberta, Canada, presents a unique opportunity to investigate in detail the transition from fluvial incised-valley fills to open marine mudstone using over 1000 wells, over 400 with core, from an area of 3,200 km2. The presence of prominent marine well-log markers and the abundance and density of well logs allows confident correlation of the incised-valley fills. The Clearwater Formation consists of 13 stacked incised valleys with depths of incision ranging from 30 m to possibly 120 m. All of the valley fills show a depositional facies pattern from sandy fluvial or upper estuarine updip to muddy estuarine or marine deposits downdip. All of the valleys terminate downdip as thin (< 2 m) sheets of marine sandy mudstone. Significantly, none of the valleys are connected to downdip lowstand deltas, or even sandy lowstand shorelines. In addition, the valley-fill lithofacies differ significantly from the marine strata into which they are incised; they are sandier, and the sand fraction is coarser. The valley fills, therefore, are not composed only of reworked material eroded from valley walls, but represent sediment delivered from more proximal sources, presumably by rivers.

Our examples demonstrate that the presence of deep incised valleys, even if they are filled with coarse material, cannot by itself be used to predict sand delivery to the paleo-shoreline or more basinward regions. We recognize two primary conditions for valley fills that lack associated sandy lowstand deposits: the lowest point of relative sea level was above the continental shelf edge (for passive-margin settings), and sediment delivery during early rising sea level was limited. For the examples cited we interpret that filling of incised valleys occurs during relative sea-level rise when only limited amounts of sediment can be delivered beyond incised-valley mouths.

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SEPM Special Publication

Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy

Gray J. Hampson
Gray J. Hampson
Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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Ronald J. Steel
Ronald J. Steel
Department of Geosciences, Jackson School, University of Texas at Austin, Austin, Texas 78712, U.S.A.
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Peter M. Burgess
Peter M. Burgess
Shell International Exploration and Production, Kessler Park 1, P.O. Box 60, 2280 AB Rijswijk, The NetherlandsPresent address: Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
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Robert W. Dalrymple
Robert W. Dalrymple
Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada
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SEPM Society for Sedimentary Geology
Volume
90
ISBN electronic:
9781565763180
Publication date:
January 01, 2008

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