LA-ICPMS U–Pb Dating of Zircon in Paleotsunami Deposits from Miyazaki Plain, Southwest Japan

Abstract

 U–Pb dating of detrital zircons was performed to characterize the paleotsunami deposits of the 1662 CE Kanbun-Hyuganada sea earthquake in the SY05 core from the Miyazaki plain on the Pacific coast of southwest Japan. Twenty-five large-sized zircon grains (> ∼50 μm) were separated from the paleotsunami deposits by chemical abrasion. In the present work, ²³⁸U–²⁰⁶Pb ages were measured by a laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-ICPMS) system at Tono Geoscience Center, Japan Atomic Energy Agency. ²³⁸U–²⁰⁶Pb ages of the detrital zircons ranged from ∼14 Ma to ∼2405 Ma, and the age spectrum revealed high relative probability values around ∼100 Ma and ∼2000 Ma. Detrital zircons with the age of ∼100 Ma in the 1662 CE paleotsunami deposits could be partly originated from the Shimanto Supergroup (Cretaceous–Paleogene) in Kyusyu Island, southwest Japan. Moreover, the U–Pb age spectrum of detrital zircons with Precambrian grains from the paleotsunami deposits was similar with those of fore-arc sandstones from central Kyushu Island.