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Recent progress in understanding of early Earth biosphere

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doi: 10.14934/chikyukagaku.50.177
Authors:Ohtomo, Yoko
Author Affiliations:Primary:
Hokkaido University, Faculty of Engineering, Hokkaido, Japan
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title:Early Earth chemistry
Volume Authors:Furukawa, Yoshihiro, prefacer; Takano, Yoshinori
Source:Early Earth chemistry, prefaced by Yoshihiro Furukawa and Yoshinori Takano. Chikyukagaku (Tokyo. 1967) = Geochemistry (Tokyo. 1967), 50(3), p.177-186. Publisher: Nihon Chikyukagakukai, Tokyo, Japan. ISSN: 0386-4073
Publication Date:2016
Note:In Japanese with English summary. 84 refs.; illus.
Summary:When the first biosphere was formed on the early earth has been actively discussed recent years. Oldest biogenic graphite and microfossils have been repeatedly tested from early 2000s, due to unclear geological settings and discovery of abiotic production of organic compounds in native environments. Here, I introduce our discovery of novel graphite-rich metasedimentary rocks in the northwest of ca. 3.8 billion-years-old Isua Supracrustal Belt, western Greenland by detail geological investigation. Isotopic and nano-scale structural signatures of graphite show that graphite is originated in biogenic organic matter, providing further oldest evidence of biological activity in the ca. 3.8 Ga ocean. Evidence of early biosphere could be found outside of carbonaceous materials in old rocks. Banded iron formations, chemical marine sediments including Fe-bearing minerals, have been a subject of active research connecting redox state to biosphere on early earth's surface. Previous studies indicate that atmospheric oxygen increased at ca. 2.45 Ga (Great Oxidation Event: GOE), suggesting that oxygenic photosynthesizing bacteria have been flourished and emitted oxygen. However, more recent geological and geochemical records reveal that shallow part of ocean and atmosphere have been slightly oxidized before GOE, which evokes that oxygenic photosynthesizing bacteria was active earlier than that anticipated.
Subjects:Archean; Banded iron formations; Biogenic processes; Biosphere; Chemically precipitated rocks; Earth; Geochemistry; Graphite; Great Oxidation Event; Iron formations; Metamorphic rocks; Microorganisms; Native elements; Organic compounds; Photochemistry; Photosynthesis; Precambrian; Proterozoic; Sedimentary rocks; Supracrustals; Upper Precambrian; Arctic region; Greenland; Isua Belt; West Greenland; Bacteria
Coordinates:N600000 N640000 W0500000 W0600000
Record ID:788202-5
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute.
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