The ocean silica cycle recorded in Paleozoic to Mesozoic deep-sea sedimentary rocks

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K23470
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Muto Shun 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, 研究員 (80849951)
• Project Period (FY): 2019-08-30 – 2023-03-31
• Keywords: 深海堆積岩 / 超海洋パンサラッサ / コノドント / チャート / 石炭紀 / ペルム紀

Outline of Final Research Achievements

In order to reconstruct the record of silica deposited on the deep-sea floor of the past superocean, this study investigated the lithology of rocks forming the strata that were deposited in the deep sea about 300 to 250 million years ago. Index fossils (conodonts) were detected from the strata and the age of the strata was determined based on the known correspondence between geological age and fossil types. It was shown that rocks deposited in the pelagic zone of the superocean from 310 million to 150 million years ago are mostly composed of silica-rick chert. On the other hand, anomalously clay-rich rocks were deposited around 300 to 280 million years ago due to local influx of fine-grained clay particles at the studied sites.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

現在までの大洋の深海底の堆積岩層の研究は主に2.5億年前以降を対象としており、それ以前の時代の地層については岩石の特徴についても断片的な研究成果が多かった。本研究では3.1億年前から2.5億年前の地層がそれ以降と同様の堆積作用で形成されていたことを示唆する。一方、大洋の深海地層は一般的に局所的な影響を受けにくいとされるが、一部の地層では局所的な影響も反映しており、近接する地点の同時代の堆積岩層を比較することでそれを読み取れることを示した。