Growth and linkage of a segmented normal fault zone; the Late Jurassic Murchison–Statfjord North Fault, northern North Sea

Abstract

The structure of the 25km long northeastern portion of the Murchison–Statfjord North Fault Zone and adjacent syn-rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c.30.5myr of Late Jurassic, North Sea rifting. Based on a structural analysis (D–d data) alone, approximately 14 precursor fault strands are identified. Incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution. Three main stages in the evolution of the fault zone are recorded in the syn-rift stratigraphy and are biostratigraphically constrained. These are: (1) following initiation of rifting, six isolated fault strands developed (each <4km long) and controlled the stratigraphy for c.13myr; (2) the isolated strands linked along-strike forming two >9km long fault segments separated by a 2km wide relay ramp, that controlled the stratigraphy for at least the following c.10.5myr; and (3) the two fault segments hard-linked forming a single, continuous fault trace during the final c.7myr of rifting. The results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones. The results may also help to further constrain models of fault evolution.