Growth and linkage of a basin-bounding fault system: Insights from the Early Cretaceous evolution of the northern Polhem Subplatform, SW Barents Sea

Abstract

Normal faults grow by either simultaneous increase in displacement and length (isolated model), or by rapid establishment of their final length before accumulating significant displacement (constant-length model), or a combination of these tow end-members. In this study, we integrate stratigraphic and structural observations with throw backstripping and time thickness maps to define the growth processes of a basin-bounding normal fault in the northern Polhem Subplatform, SW Barents Sea. During the initial 15 My of Early Cretaceous rifting, the fault system consisted of at least five en-echelon segments, which were ca. 5–10 km long. Throw backstripping indicates that fault segments were hard-linked after this initial stage to form a single 40 km long fault zone. Fault linkage resulted in displacement redistribution, with the locus of faulting being shifted from the center of each paleo-segment, to the center of the through going fault. Across fault incised valleys provide additional information on the topographic response to fault growth. Major valley incisions at the fault linkage zones outline the extent of the individual fault segments and support early isolated fault growth. Fault backstripping results suggest that valley incision and sedimentation rates kept up with fault slip rate, such that the incised valleys remained unaffected by the uplift of the latter fault linked stage. This study illustrates the importance of integrating stratigraphic and structural observations when reconstructing the evolution of basin-bounding normal faults. In particular, syn-rift erosional features, sediment thickness variations, sediment distribution, stratal geometries and onlap/truncation relationships are critical for estimating the growth of these structures.