See more from this Division: Topical Sessions
See more from this Session: From Quaternary Geology and Physical Volcanology to Geoarchaeology and Paleoanthropology: A Memorial to Harold E. Malde
Abstract:
Excavations at the Monzen site by the Nagasaki Prefectural Government since 2002 have shown how the basaltic gravels and associated muds and sands were deposited during the last 7000 years. The source of the basalts is thought to be landslide debris in the upper reaches of the Ainoura River that were deposited by the Hokusyo earth slide.' Comparison of geological sections along the Ainoura River and the nearby Hino River supports this theory. Within the alluvial succession, the top surface of the deposits (sands and muds) rose suddenly during 6500-6000 B.P., then stopped rising. The gravels began to deposite about 3000 B.P., then their depositional elevation has been raised due to the rising of the river bed.
The Monzen remains show evidence that the settlement was hit by catastrophic rock avalanches on more than one occasion, prompting the question as to why people chose to live there. The present study has shown that the paleogeography of the time was suitable for gathering food from the sea and the forest, and rice cropping.
Important structures such as houses and paddocks were built on the adjacent higher ground. The frequency of the destructive debris flows is estimated as once every several hundred years, which makes the settlement of the floodplain seem reasonable.
See more from this Division: Topical Sessions
See more from this Session: From Quaternary Geology and Physical Volcanology to Geoarchaeology and Paleoanthropology: A Memorial to Harold E. Malde