Slump strain indicative of paleoslope in Cretaceous Izumi sedimentary basin along Median tectonic line, southwest Japan

Submarine slump folds are common in turbidites of the Izumi Group (Upper Cretaceous), south of Osaka in southwest Japan. Structural analysis of the folds indicates predominantly eastward movement of the slump sheet. However, it is noteworthy that this direction is generally opposite to westward paleocurrents obtained from sole marks, but it coincides with the direction of younging of the strata and the plunge direction of macroscopic synclines in the Izumi Group. The paleoslope inferred from the slump folds is believed to have been caused by the eastward migration of the depocenter of the Izumi sedimentary basin. This slumpi ng is thought to have followed tilting of the beds deposited by the westward current. The migration of the depocenters and tilting are associated with left-slip faulting on the bounding Median tectonic line.