Late syn-rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid-Norway; a test of rift basin tectono-stratigraphic models

Rift basin tectono-stratigraphic models indicate that normal fault growth controls the sedimentology and stratigraphic architecture of syn-rift deposits. However, such models have rarely been tested by observations from natural examples and thus remain largely conceptual. In this study we integrate 3D seismic reflection, and biostratigraphically constrained core and wireline log data from the Vingleia Fault Complex, Halten Terrace, offshore Mid-Norway to test rift basin tectono-stratigraphic models. The geometry of the basin-bounding fault and its hangingwall, and the syn-rift stratal architecture, vary along strike. The fault is planar along a much of its length, bounding a half-graben containing a faultward-thickening syn-rift wedge. Locally, however, the fault has a ramp-flat-ramp geometry, with the hangingwall defined by a fault-parallel anticline-syncline pair. Here, an unusual bipartite syn-rift architecture is observed, comprising a lower faultward-expanding and an upper faultward-thinning wedge. Fine-grained basinfloor deposits dominate the syn-rift succession, although isolated coarse clastics occur. The spatial and temporal distribution of these coarse clastics is complex due to syn-depositional movement on the Vingleia Fault Complex. High rates of accommodation generation in the fault hangingwall led to aggradational stacking of fan deltas that rapidly (<5km) pinch out basinward into offshore mudstone. In the south of the basin, rapid strain localization meant that relay ramps were short-lived and did not represent major, long-lived sediment entry points. In contrast, in the north, strain localization occurred later in the rift event, thus progradational shorefaces developed and persisted for a relatively long time in relay ramps developed between unlinked fault segments. The footwall of the Vingleia Fault Complex was characterized by relatively low rates of accommodation generation, with relatively thin, progradational hangingwall shorelines developed downdip of the fault block apex, sometime after the onset of sediment supply to the hangingwall. We show that rift basin tectono-stratigraphic models need modifying to take into account along-strike variability in fault structure and basin physiography, and the timing and style of syn-rift sediment dispersal and facies, in both hangingwall and footwall locations.