Is the peat bed in the Kanto Plain rework of kuroboku soil?

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03690
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Tanabe Susumu 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 上級主任研究員 (50415709)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 関東平野 / 中川低地 / 泥炭層 / 黒ボク土 / 黒泥 / 弥生の小海退

Outline of Final Research Achievements

In the Nakagawa and Kazo lowlands in the central Kanto Plain, so-called peat layers are widely distributed around 0 m elevation. However, unlike ordinary peat composed of undecomposed plant material, this peat layer is composed mainly of fine-grained organic material and thickens upstream of the alluvial lowlands and along the margins of the uplands. In this study, sediment core analysis and high-density radiocarbon dating were conducted to elucidate the formation mechanism of the peat layers. As a result, the peat layers in the Nakagawa Lowland are mainly composed of local muck, as initially suggested as one of the possibilities, and the reason for the widespread development of peat layers in the inland is that the bypass of clastic materials in the upper reaches and the deposition of clastic materials in the lower reaches were synchronized with the Yayoi regression.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

濃尾平野や豊川平野，矢作川下流低地には，弥生の小海退に伴って形成されたと考えられる埋積浅谷の基底部に泥炭層が厚く発達する．近年，埋積浅谷の形成要因として，堆積中心の海側への移動に伴う，内陸側における侵食と海側における堆積の同時進行が提唱されている．本研究は，多数の堆積物コアと放射性炭素年代値に基づいて，このような埋積浅谷の形成モデルと泥炭層の発達さらには海水準変動との関係を明確にしたものであり，関東平野と東海地方には類似した泥炭層の形成メカニズムがあったことを示唆する．本研究は，関東平野中央部における流域全体を捉えた泥炭層の発達モデルを構築できた点に意義がある．