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SUMMARY:The geologic history of marine dissolved organic carbon from iron 
 (oxyhydr)oxides - Jordon Hemingway\, ETH Zurich
DTSTART:20240604T110000Z
DTEND:20240604T120000Z
UID:TALK215353@talks.cam.ac.uk
CONTACT:Dr Rachael Rhodes
DESCRIPTION:Dissolved organic carbon (DOC) is the largest reduced carbon r
 eservoir in modern oceans. Its dynamics regulate marine ecosystems and atm
 ospheric CO2 levels\, whereas 13C compositions track autotrophic metabolis
 m. However\, the geologic history of marine DOC remains entirely unconstra
 ined. To address this\, we developed the first direct proxy for past DOC s
 ignatures using co-precipitated organic carbon in iron ooids\, and we appl
 ied this to 25 marine iron ooid-containing formations deposited over the p
 ast 1650 million years. Predicted DOC concentrations were near modern leve
 ls in the Paleoproterozoic then decreased by 90-99 % in the Neoproterozoic
  before sharply rising in the Cambrian. Furthermore\, Proterozoic DOC was 
 significantly 13C-depleted relative to today. I will discuss how trends li
 kely reflect coupled changes in ocean oxygenation\, particle export flux\,
  and autotrophic 13C fractionation through geologic time.
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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