Application of extensional models to the Northern Viking Graben

Subsidence curves corrected for compaction, estimated water depths of deposition, and changes in sea
level from the Northern Viking Gra ben are matched to a uniform, two-phase, time-dependent extensional
model. Total subsidence along the graben axis suggests a total extension of approximately 1.8, consisting
of a Triassic extension of 1.5 and a Late Jurassic extension of 1.2. Within the graben, the model predicts
subsidence very well, but the flanks are problematic. A more complicated model involving depth
dependent stretching, mantle convection, or isostatic uplift of individual fault blocks may be needed to
explain the uplift/non-subsidence of the graben flanks during rifting. Geometry of rotated fault blocks
in the area accounts for extension of between 1. 1 and 1.3, which is consistent with the Late Jurassic
event. Although Triassic faulting is clearly seen on the eastern margin of the basin, early phase faulting
in the graben axis has probably been rotated by the later tectonic activity and is not clearly imaged due
to its depth and orientation. Crustal thinning determined from recent deep reftection and older refraction
profiles suggest an extension of approximately 2. 0, which is compatible with the observations of total