1999 GSA Annual Meeting -- Denver, Colorado
Author(s): DEIBERT, Jack, Dept. of Geology, Austin Peay State University, Clarksville, TN 37044, firstname.lastname@example.org; BENDA, Tara; LOSETH, Tore; SCHELLPEPER, Maija; and STEEL, Ron, Dept. Geology, University of Wyoming, Laramie, WY 82071
Keywords: Spitsbergen, deepwater-sand, clinoform, shelf-slope, storm-wave
Large-scale clinoforms are observed in outcrops of the Eocene Battfjellet Formation of south central Spitsbergen, Norway. The clinoforms formed as accretionary infill of an active foreland basin. Several types of clinoforms are recognized, but this study focuses on clinoforms associated with a marine storm-wave regime on the shelf, which provided only modest volumes of sand to the slope and no sand onto the basin floor. The clinoforms can be traced over 3500 m in a basinward direction, have slope segments at least 2100 m wide, and have an average vertical relief of 130 m. Average angles along the entire length of the clinoforms range from 0.9 to 2.5 degrees, with slope segments ranging from 4.2 to 7.6 degrees. Sandstone units (clinothems) that define the clinoforms are 2 to 12 m-thick and are separated by shale units up to 70 m-thick. Shelf and upper slope segments of clinothems are dominated by hummocky cross-stratification whereas lower slope segments are dominated by plane-parallel lamination. Individual sandstone clinothems are interpreted to have formed by basinward shoreline progradation during short periods of very slow relative sea-level rise or standstill. Evidence of sand by-passing the slope during these periods of basinward progradation is absent. Intervening shale units developed during longer intervals when relative sea-level was rising significantly and sandy sediment volumes were being stored farther landward. The overall shelf-edge trajectory, formed by the succession of clinothems, shows a significant aggradational component, indicative of an overall rise in relative sea level. The clinothems are very similar in amplitude, angle, and individual shape to clinothems that bring great volumes of sand onto the basin floor and slope. However, the storm-wave-dominated clinothems are distinctly different in their aggradational trajectory and lack of incision into older shelf strata. These two distinguishing features may be used to predict the likely absence of large volumes of slope and basin-floor sand.
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