Abstract: Tectonic and Sedimentologic Influences on Cycles During The Middle to Upper Jurassic, Viking Graben, North Sea

John S. Sneider, Philippe de Clarens, Peter R. Vail

Seven second order regressive/transgressive (R/T) cycles were deposited during an overall transgression from the Lower Toarcian to the base of the Cretaceous. The PVT cycles correlate throughout the Viking Graben area. Three second order cycles occur during an early/pre-rift phase and four during a syn/post-rift phase. Each cycle corresponds to a phase of rifting in the region; however individual faults are not active during each rift phase Fault activity and margin uplift increase local sediment supply Cycles are also recognized in areas with little fault activity.

The regressive phases formed during periods of high regional fault activity; subsidence concentrated in the graben center and was low on the graben flanks. Shelfal areas and local highs were often eroded. Highly variable fault induced subsidence caused the peak regression to vary by as much as 4 million years. The transgressive phase formed during periods of regional subsidence and lower fault activity. Peak transgressions are regionally synchronous, associated with more regional subsidence, and used to divide the cycles.

Basin geometry and sediment supply influence cycle development. Areas with high sediment supply and steep slopes develop thick, coarse-grained turbidites; no prograding wedges develop. On gently dipping slopes, prograding wedges develop without the formation of thick turbidites. When sediment supply is high, third order cycles are well developed. When sediment supply is low, third order cycles are suppressed.

These R/T cycles provide a powerful framework for regional correlation and regional facies prediction in a region with variable tectonic settings and sedimentation rates.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994