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Submarine canyon formations and tectonics and climate changes in late Pliocene on forearc shelfin northern Japan

日本北部弧前陆架上新世晚期海底峡谷的形成、构造和气候变化

基本信息

批准号：
18540451
负责人：
HOYANAGI Koichi
金额：
$ 2.43万
依托单位：
Shinshu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540451/
关键词：
Pliocene Dainenii Formation shelf organic matter climate change submarine canyon stable carbon isotope diatom fossil 大年寺層金津層環境変動テクトニクス陸棚の堆積作用

项目摘要

Pliocene Dainenji Formation is distributed in the Pacific side of the Fukushima Prefecture. The Dainenji Formation is deposited on shelf environment and consists mainly of sandy siltstone and sandstone. It includes a number of volcanic ash layers, which serve as good key beds useful for precise correlation. Its depositional age is from 4.18 to 2 Ma. We carried out facies and geochemical analyses, such as total organic carbon (TOC), total sulfur (TS), and stable carbon isotope ratio of organic matter (δ^(13)C_org). The results are as follows: (1) Abundant land-derived organic matter was transported to the shelf and was preserved in the sediment in warm period (3.75-305 Ma). (2) productivity of marine organisms increased in the early cooling period (3.5-3.35 Ma),. (3) The considerable variations in TS, TOC andδ^(13)Corg are seen in cooling stage after 3 Ma, which succeeded to the Quaternary ice age. These considerable variations are shown inδ^(18)O curve of the same age.Mappable units of submarine canyon-fill sediment are recognized in this area. A valley has a maximum depth of 100 m and is considered to be formed by submarine landslide, which took place after 2.7 Ma. Submarine canyon-fill sediments are composed of siltstone interbedded with thin sandstone layers, thick sandstone beds and slump deposits. Formation and filling of the submarine canyon might be controlled by climate cooling of latest Pliocene age.

上新世Dainenji组分布在福岛县太平洋一侧。代南基组沉积于陆架环境，主要由砂质粉砂岩和砂岩组成。它包括许多火山灰层，这些火山灰层是进行精确对比的关键层。其沉积年龄为4.18 ~ 2 Ma。进行了总有机碳（TOC）、总硫（TS）、有机质稳定碳同位素比值（δ^(13)C_org）等相分析和地球化学分析。结果表明：(1)暖期（3.75 ~ 305 Ma）大量陆源有机质被搬运至陆架并保存在沉积物中。(2)海洋生物生产力在降温初期（3.5 ~ 3.35 Ma）呈上升趋势；(3) TS、TOC和δ^(13) cog在第四纪冰期之后的3 Ma冷却阶段发生了较大的变化。相同年龄的δ^(18)O曲线显示了这些相当大的变化。发现了海底峡谷充填沉积物的可测绘单元。山谷最大深度100米，被认为是2.7 Ma后发生的海底滑坡形成的。海底填谷沉积由粉砂岩与薄砂岩层、厚砂岩层和滑塌沉积互层组成。海底峡谷的形成和充填可能受上新世晚期气候变冷的控制。