Holocene turbidite cores from the southern Ryukyu Trench slope: suggestions of periodic earthquakes

Abstract

Three piston cores were extracted from three different turbidite fans developed near a coral reef region in the southern Ryukyu Island Arc, northwestern Pacific Ocean. The ages of these cores were determined by AMS (accelerator mass spectrometer) 14C dating and two planktic foraminiferal δ18O events. Many turbidity currents, recognized in the studied cores, were triggered mainly by earthquakes. We hypothesize that the age discrepancies of the turbidite layers, from core to core, were due to differences in the source areas and passages (submarine canyons) of the respective turbidity currents. A core from the youngest fan suggests that turbidity currents frequently occurred after ~10 Ka with ~1000 yr interval on average, possibly in relation to periodical earthquakes. This possibility is demonstrated in a multi-channel reflection survey over ~113km, near the core-sites, where a recent accretionary prism was recognized.