--> Abstract: Deepwater-Slope Channels and Hyperpycnal Flows from the Eocene of the Central Spitsbergen Basin: Predicting Basin-Floor Sands from a Shelf Edge/Upper Slope Perspective, by Andrew L. Petter and Ronald J. Steel; #90039 (2005)

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Deepwater-Slope Channels and Hyperpycnal Flows from the Eocene of the Central Spitsbergen Basin: Predicting Basin-Floor Sands from a Shelf Edge/Upper Slope Perspective

Andrew L. Petter and Ronald J. Steel
University of Texas-Austin, Austin, TX

Stacked hyperpycnal flow deposits, characterized by thick, erosively-based, plane-parallel laminated beds with ripple caps, constitute the predominant channel fill in an early Eocene shelf-edge/upper-slope clinoformed system in Spitsbergen. This system is attached to a basin-floor fan via slope channels, making it an ideal study of a deepwater sand-feeder system.

Hyperpycnites on the basin-floor and slope contain well-preserved plant leaves, suggesting direct connection of these environments with a strong fluvial discharge at the shelf edge during lowstand. Hyperpycnites and slumps dominate outer shelf and shelf-edge deltaic deposits, highlighting the importance of fluvial domination and rapid deposition in forced regressive shorelines at the shelf edge.

Slumped blocks and thickened fill on the upper slope suggest that sediment flows were initially focused in canyon heads formed by shelf-edge failure. Overbank wings and levee deposits become prevalent on the middle to lower slope, implying relatively unconfined flow through constructional channels. Channel-margin attached, laterally accreting hyperpycnite bars up to 5 meters thick fill scours cut into slope muds and early slope-channel fill and are interpreted as constructed by sustained river flooding.

The base of the canyon thalweg contains the coarsest sands. These deposits are massive with occasional shale/silt filled scours, suggesting early bypass of sands to the basin-floor. Overlying hyperpycnal flows were deposited within slope channels. Healing of the canyon scar was accomplished by a slope fan of thin-bedded turbidites and the initial parasequence of the late-lowstand wedge, a heterolithic downlapping deltaic unit. This in turn is overlain by mudstone and the maximum flooding surface.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005