The landform evolution of Late Pleistocene in the Miyazaki Plain, south Kyushu, Japan.

Abstract

The oldest marker tephra layer on the Sanzaibaru surface is the Ata ash which erupted from the Ata caldera ca. 90 000-80 000 y BP. The Sanzaibaru surface underlying the Ata ash is thought to have emerged ca. 100 000 y BP, in the Last Interglacial stage. It is estimated by subtracting the height of the base of the Sanzaibaru Formation from the height of the shoreline of the surface that sea level rose more than 100m in the Sanzaibaru stage. The Nyutabaru I,II,III surfaces are characterized by gentle gradients and wide distribution; they are of fluvial origin. The Nyutabaru III surface is an accumulation terrace formed during the little transgression. These surfaces are thought to have emerged ca. 90 000-60 000 y BP, when a relatively high sea level was maintained because regression was slow and debris supply from the Kyushu Mountains increased or discharge in rivers decreased. The Saitobaru I and II, Oyodo and Kunitomi I and II surfaces, which are characterized by steeper and more linear longitudinal profiles, are erosional terraces and are mostly of fluvial origin. Their surfaces came out ca. 50 000-10 000 y BP in the Last Glacial Stage, when rapid regression occurred and sea level stayed relatively lower. The Karasebaru, Toyobaru I and II and Mikazukibaru I and II surfaces in the northern part of the plain are fluvial fans.-from English summary