HOW THE ARCHITECTURE OF HYPEREXTENSION CONTROLS THE SOURCE OF PASSIVE MARGIN SEDIMENTS: AN EXAMPLE FROM THE NORWEGIAN SEA

Passive margins host important petroleum systems. Because the understanding of extended margin architecture has recently undergone significant revision, new exploration models have been developed to incorporate interpretations made under the paradigm of hyperextension. Although passive margins derive directly from extended margins, few studies have described the effect of offshore architecture on the post-breakup structural and topographic evolution of hyperextended crust.

A scaling relationship linking the post-rift passive margin escarpment elevation to an offshore zone that reflects the zone of deformation decoupling during high-beta extension was identified by Osmundsen & Redfield (2011). The scaling relationship is independent of variables such as magmatic style, mantle upwelling, or glacial history, and appears valid for hyperextended passive margin sectors on several continents. It suggests post-breakup topographic rejuvenation occurs where thinning phase detachment faults excised much of the crystalline crust over short horizontal distances, whereas minimal to no reactivation occurs inboard of less dramatically thinned crust. This may possibly be due to a rock-breaking increase in flexurally-related tensile stress in response to the accumulation of an offshore 'sag' basin sedimentary load

Peppered by extensive, high-quality marine geophysical data, the NE Atlantic Norwegian margin offers an excellent test of the “Taper Hypothesis.” Redfield & Osmundsen (2013) documented landform characteristics typical of tectonic topography and showed how physical distance from the offshore zone of deformation coupling (the Taper Break) controlled the topographic and geomorphic response of the Norwegian escarpment and its hinterland.

The Taper Hypothesis has source-to-sink implications for petroleum exploration. It predicts post-breakup reactivation of normal faulting on sharply-tapered sectors of the emergent proximal margin is an inevitable process. It also predicts that margin escarpments adjacent to sharp crustal tapers are likely to be under a significant level of fault control, undergo periodic footwall uplift events, and constitute important sources of post-breakup sediment which can be transported along fault-controlled fairways to taper-controlled deep basin sinks.