Study of Cretaceous tectonics along the east margin of Asia based on detrital zircon U-Pb and Hf model ages

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05677
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: University of Toyama
• Principal Investigator: Otoh Shigeru 富山大学, 学術研究部都市デザイン学系, 教授 (60194221)
• Co-Investigator(Kenkyū-buntansha): 山本 鋼志 名古屋大学, 環境学研究科, 教授 (70183689)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 白亜系 / ジュラ系 / 極東ロシア / 沿海州 / 後背地解析 / 砕屑性ジルコン / ウラン－鉛年代

Outline of Final Research Achievements

We studied the detrital-zircon-age spectra of Jurassic to Cretaceous sandstone samples from Far East Russia and Hokkaido to elucidate the Mesozoic crustal disturbance along the active continental margin of east Asia. The north-trending and westward-dipping Khabarovsk-Amur Complex (C) and Samarka-Zhravlevka C in Far East Russia with the maximum depositional ages of sandstone gradually younging downwards are two parallel juxtaposed accretionary complexes. Taking the Yezo Group (forearc-basin sedimentary rocks) and the Idon’nappu accretionary C of Hokkaido, northern Japan, the Cretaceous arc-trench systems make three parallel rows from Far East Russia to Hokkaido. The detrital-zircon-age spectra indicate that the Jurassic-Cretaceous sandstone of Far East Russia was deposited near the present distribution area. On the other hand, the Yezo sedimentary basin was likely shifted northward from South China to its present position in the Cretaceous.

Free Research Field

構造地質学，テクトニクス

Academic Significance and Societal Importance of the Research Achievements

日本列島から極東ロシアに至る地質構造の大局的枠組みを解明した点が，本研究の学術的意義である。従来，日本列島では，古生代地質体やジュラ紀付加体が複列に分布することが知られており，そのでき方が議論されてきた。本研究は，極東ロシアから北海道にかけて，日本には四万十帯にしか見られない白亜紀付加体が，アムールC，ジュラブレフカC，イドンナップCの三列に分かれることを解明した。一方，古生代地質体は，極東ロシアで分布が一列になる。この様な地質体の分布は，アジア大陸東縁全体が左横すべり複合断層帯（sinistral strike-slip duplex）をなすことを示す。