Sedimentation processes and basin‐filling depositional architecture in an active asymmetric graben: Strava graben, Gulf of Corinth, Greece

Abstract This paper presents data on the sedimentation processes and basin‐fill architecture in an incipient submarine intrabasinal graben, the Strava graben. The Strava graben is a relatively small intrabasinal structure about 15 km long and 3 km wide formed some time during the late Pleistocene. It connects the Alkyonidhes basin to the Corinth basin, in the Aegean back arc, which is characterized by fast rates of extension and intensive seismicity. Analysis and interpretation of high‐resolution 3.5‐kHz and sparker profiles together with sonar imagery have shown that gravity‐driven sediment transport, triggered by earthquakes, is the dominant sedimentation process and that this sediment forms the vast bulk of the basin‐fill. The sediment deposited in the Strava graben is derived from the uplifted footwall blocks bounding the graben and is transported to the basin initially as liquefied flows, some of which may progressively evolve to turbidity flows. The deposits of the liquefied flows have accumulated in the graben floor as aggradational stacks, consisting of sheet‐like, low‐relief lobes, forming base of slope aprons that are fed by multiple sediment sources along active faults. In addition to the lateral (footwall‐derived) sediment transport there is also a gravity‐controlled axial transport. The axial transport has formed a depositional system in the down‐dip termination of the Strava graben, where it enters the Corinth basin. The axial depositional system grows outwards and upwards and consists of liquefied flow depositional lobes which are separated by turbidites. The sedimentation transport processes and basin infilling style described for the Strava graben can be used as a predictive model for the early synrift stage of ancient submarine intrabasinal structures, in which the major sediment source area is the bounding fault scarps and not drainage basins in the hinterland.