島根県,神原第2遺跡の三瓶火山太平山火砕流堆積物の定置温度見積もり : 縄文人は被害を受けたか?

Many archeological sites including Jomon remains occur along the Kando River，Shimane Prefecture．Some Jomon remains are directly covered by Taiheizan pyroclastic flow deposits which originated from the Holocene Sanbe Volcano nearby．Carbonized woods from the pyroclastic flow deposits have previously been dated by ^<14>_C method at 3530±100 and 3700±130y.B.P．The pyroclastic flow deposits are block-and-ash flows．They contain many carbonized wood fragments，which may reach a length of 468 cm and a diameter of 30 cm．Flow emplacement temperatures were estimated from paleomagnetic blocking temperatures of clasts and H/C thermometry of carbonized wood fragments．Accidental fragments in the deposits were heated up to 530-560℃，and temperatures estimated from carbonized woods reach 545℃．Although the Taiheizan pyroclastic flow was not large and the archeological sites are about 5.5 km from the conduit，emplacement temperatures are very high．It is inferred that some Jomon people suffered from the pyroclastic flow，because of its power and the strong thermal effect on the surrunding area．Estimation of emplacement temperatures of pyroclastic flow deposits plays an important role in the drawing of volcanic hazard maps．