Changes in planview geometry and erosion–deposition patterns along a channel–levee complex in the southern corner of the Kurile Basin, Okhotsk Sea

High-resolution seismic profiles reveal the changes in planform and erosion/deposition pattern in the Abashiri-oki Trough (AOT), the southwestern corner of the Kurile Basin. The AOT originated from a syncline in the Late Miocene–Early Pliocene, and is characterised by Plio-Pleistocene channel–levee complexes and debris flows, mainly composed of hummocky, chaotic and convergent reflectors. The channel planform was changed by eustacy, tectonics, climate, and hinterland volcanism. Regressive surfaces probably occur as the two reflectors of erosional surface and debris flow deposits. The erosional/depositional pattern suggests that the channel profile tends to evolve towards an exponential-like form. In the upper trough, channels are incised. Probably inland volcanism induced to increase sedimentary supply, consequently the slope progradation and steepened gradient. Volcanism also caused an additional channel. In the middle trough, channels show braided pattern, related to subsidence and mildened gradient of the trough floor, which lead to accommodation. In the lower trough, channels anastomose, and in the lowermost trough finally, the merged channel incises and cut-offs the anticline dividing the AOT from the Kurile Basin.