Holocene Environmental History in the Kazo Lowland, Central Kanto Plain

EGUCHI Sei-ichi, MURATA Taisuke

doi:10.4157/grj1984a.72.4_253

Fossil diatom and phytolith results with a dozen ¹⁴C datings, and investigation into the stratigra-phy and sedimentary facies of borehole cores from the Kazo Lowland, central Kanto Plain, were used to reconstruct the Holocene environmental history.<br> The Pleistocene uplands had been dissected by narrow valleys before ca. 30, 000 years ago. From the Last Glacial maximum to the early Holocene, Phragmites swamps developed in these valleys.<br> The Jomon transgression caused the subsequent maximum stable sea level in the Kazo Lowland ca. 7, 000 years ago. Because marine areas invaded the valleys, inner bays were formed and the ma-rine flats expanded gradually. After ca. 5, 300 years ago, brackish environments were dominant be-cause of regression and increase in fluvial activity. After ca. 3, 500 years ago, the brackish flats were transformed into river mouths or down stream river stretches due to successive sedimentation of fluvial deposits.<br> After ca. 2, 000 years ago, the valleys were filled and flood plains were formed. Fluvial deposits began to spread over Pleistocene uplands rapidly ca. 1, 500 years ago. Large natural levees have been developed, covering a wide area.

Holocene Environmental History in the Kazo Lowland, Central Kanto Plain

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