A regime shift in the geobiota around the Proterozoic-Phanerozoic boundary in the Dzabkhan Terrane, western Mongolia

2017 Fiscal Year Final Research Report

• Project/Area Number: 15H03744
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Stratigraphy/Paleontology
• Research Institution: Osaka City University
• Principal Investigator: EZAKI Yoichi 大阪市立大学, 大学院理学研究科, 教授 (60221115)
• Research Collaborator: ADACHI Natsuko 大阪市立大学, 大学院理学研究科, 准教授 (40608759) ; TOKUDA Yuki 公立鳥取環境大学, 環境学部, 講師 (30779765) ; SENTOKU Asuka 琉球大学, 理学部, 助教 (00722802)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 原生累代 / 顕生累代 / カンブリア紀 / 礁 / モンゴル

Outline of Final Research Achievements

This study established the lithostratigraphy of the Tsagaan Oloom, Bayan Gol, and Salaany Gol formations in Govi-Altai Province of western Mongolia, and analysed their sedimentary facies. The results indicate the location of the Ediacaran-Cambrian boundary (ECB), temporal changes in ichnofacies, and the first appearance horizons of small shelly fossils as well as of calcimicrobes and calcimicrobial reefs. The calcimicrobial reefs above the ECB are represented by thrombolites and stromatolites, and the calcimicrobes Renalcis and Epiphyton are common. Flat pebble conglomerates provided structurally stable substrates for the initial and stabilising stages of calcimicrobial reefs. Archaeocyath-calcimicrobial reefs of the Salaany Gol Formation are composed of archaeocyath frameworks with variable types of growth morphology, and inter- and intraframework bindings and infillings by calcimicrobes and carbonate cement. These geobiotas are markedly different from those of the Ediacaran Period.

Free Research Field

層位・古生物学