Piret Plink-Björklund1, Ron Steel1, Jeff Crabaugh1, Donatella Mellere2
(1) University of Wyoming, Laramie, WY
(2) University of Padova, Italy
ABSTRACT: Nonmarine to Shallow-Marine to Deep-Marine Linkage, Eocene Central Basin, Spitsbergen
The excellent seismic-scale outcrops of Eocene Central Basin on Spitsbergen allow detailed examination of coastal plain to shallow-marine to deep-marine linkage within sequence a stratigraphic framework. Base-level falls are seen by regional unconformities and the shift of fluvial channels all the way to the shelf edge. Where there is significant incision of coastal plain, shelf and especially shelf edge, turbidites that transport sand into deep-water are produced on the slope. The fluvial systems stay right at the shelf edge and feed sediment onto the slope through the early base-level rise (i.e. lowstand wedge time). Surprisingly, the fluvial channels are tidally influenced in their seaward reaches even at that time. Linkage between these fluvial to tidally-influenced channels into chutes just below the shelf-edge has been "walked out". The infill of upper reaches of chutes suggests deposition from sustained flows (hyperpycnal flows). The incised valleys become flooded and transform into tidally-dominated estuaries during base-level rise. Further seaward, tidal bars alternate with shoreface deposits in a generally landward-stepping manner and several erosion surfaces mark wave or tidal ravinement. The maximum flooding superimposes shoreface deposits onto estuarine deposits. During highstand the shelf aggrades and slope progrades. Estuaries on the coastal plain start to infill, but they transform into deltas only occasionally, i.e. the bulk of sediment transport remains into the estuary throughout most of the highstands. This implies that sediment escapes the coastal-plain/shallow-marine areas and feeds the deep-water areas with turbidites only during forced regressive and lowstand wedge times.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado