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Individualization of a forearc basin during the active margin evolution: Hikurangi subduction margin, New Zealand

Abstract:

Sedimentological studies from the Hikurangi forearc domain (New Zealand) outlined a major unconformity at the Miocene-Pliocene boundary, around 6-4 My ago. This discontinuity marks the transition between two main periods, in the evolution of the active margin during the Neogene. The first one is Miocene (about 18-6My) and is characterized by a general deepening in water depths, linked to a major subsidence of the whole margin. The second period is Pliocene-Pleistocene (about 4-0 My) and exhibits the formation of a real forearc basin. This basin is an elongated narrow depression between the frontal arc (landward) and the Coastal Ranges (seaward) corresponding to the highest ridge of the accretionary wedge.