Olistostromes marking tectonics events, East Coast, New Zealand
Résumé
Three discrete, successive tectonic events are marked by olistostromes in the East Coast, North Island. An Eocene Mataikona event is characterised by in-situ dismembered beds. A second, Owahanga event is Otaian and preceded wrench faulting coeval with the start of oblique subduction at the East Coast margin. This second event is characterised by extended emplacement of exotic material followed by gliding, gravity-driven nappes that are probably related to obduction along the north coast of the North Island. The third olistostrome is attributed to an early Miocene Mara event synchronous with incipient strike-slip faulting during Altonian times and commencement of oblique convergence at the Hikurangi margin. From the ages and paleoenvironments of the olistostromes, we propose the Eocene and earliest Miocene syn-sedimentary structures were dragged along the deforming backstop of the Hikurangi prism.