Reconstruction of Three-Dimensional Stratigraphic Architecture and Sediment Storage on the Nobi Plain Based on Borehole Data Analysis Using GIS

Abstract

This study reconstructed the three-dimensional stratigraphic architecture of incised-valley fills and calculated sediment storage by analyzing 2,701 existing borehole columns and 218 radiocarbon ages using GIS in the Nobi Plain, central Japan. The latest Pleistocene to Holocene depositional sequence under the Nobi Plain were divided into six lithofacies: basal gravel (BG); lower sand (LS); middle mud (MM); upper sand (US); terrestrial sand and mud (TSM); and artificially deformed layer (AD). The valley topography found in the bases of LS and MM and the late Pleistocene terrace distributed in the eastern part of the plain were buried by the accumulation of MM and US under delta progradation. The subaerial delta expanded widely with the deposition of TSM after 1,000calBP.

Total sediment storage in the study area of 1,179.4km² during the last 6,000 years was estimated to be 21,463Tg, and the sediment storage for every 1,000-year interval was 2,359, 2,754, 3,848, 3,194, 3,748, and 5,559Tg, respectively. The sediment storage increased markedly after 1,000calBP, probably due to increased sediment production accompanying human impacts on the catchment area.