A dynamic rifting model of the Caroline Ridge, West Pacific

Abstract

The dynamic rifting model of the Caroline Ridge, an oceanic plateau in the West Pacific, remains unclear. Previous studies have revealed that the crustal width of the Caroline Ridge clearly varies from the northwest to the southeast. Here, we investigate Caroline Ridge rifting using numerical simulation and reveal the relationships between different plateau sizes and rifting. For small-scale oceanic plateaus, the initial rift migration forms a symmetric structure. The strain transfers toward one side of the margin. The rifting manifests as a process from landward migration to seaward migration, accompanied by a transition from a symmetric to an asymmetric structure. With larger initial lithospheric thinning, larger ranges of crustal deformation appear with less basement tectonic subsidence. For large-scale oceanic plateaus, basement tectonic subsidence occurs within narrower ranges. The proximal half-graben structures rapidly abandon with relatively horizontal basement and small fault offsets on the rift flank, leading to a symmetric structure during breakup. With larger initial lithospheric thinning, crustal deformation occurs within a narrower region during the early stage. Landward rift migration dominates the deformation, resulting in an asymmetric structure. On the basis of these results, for the large-scale section of the Caroline Ridge, NW-trending normal faults originated from the landward rift migration. At present, seaward rift migration dominates the Caroline Ridge deformation, forming a relatively symmetric structure. For the small-scale section of the Caroline Ridge, the initial landward rift migration occurred. Larger initial lithospheric thinning may exist beneath the Caroline Ridge during the initiation of Miocene rifting.