T161 Microfossil Proxies in Earth History (Posters)

Monday, 26 September 2016
9:00 AM - 6:30 PM
Exhibit Hall E/F

A CONSTRAINED TEST ON THE EFFECT OF ATMOSPHERIC CO2 PARTIAL PRESSURE (pCO2) ON CARBON ISOTOPE FRACTIONATIONS IN C3 PLANTS FROM CENOZOIC FOSSIL LAGERSTÄTTEN

Paper number: T161-21
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Qin Leng Presenting Author
    Bryant University, Smithfield, RI
  • Hong Yang
    Institute of Earth Environment, CAS, Xian, RI

Abstract

The stable carbon isotope (12C and 13C) signals of higher plant tissues are determined primarily by plant carbon supply (from carbon source to biochemical reaction sites) and the fractionations of carbon isotopes during biochemical reactions, two processes both influenced by plant types and various climatic/environmental parameters. Stable isotope (IRMS) analyses of exceptionally-preserved coniferous fossils (Glyptostrobus, Larix, Metasequoia, and Pseudolarix) from well-studied Cenozoic fossil lagerstätten from the Arctic suggest that the offset of δ13C values between lipid molecules and bulk tissues was maintained in a similar fashion as their modern counterparts despite a marked positive shift (~4‰) of δ13C in fossil material. Both morphological (light microscope and SEM observations) and bio-molecular (Py-GC-MS and NMR analyses) evidence suggested that this constant ~4‰ isotopic shift between fossils and their living counterparts was unlikely caused by tissue decay, and constructed models demonstrated that neither the change of δ13C in atmospheric CO2 nor the change of ci/ca ratio (the ratio of leaf intercellular and atmospheric partial pressures of CO2) can satisfactorily explain this positive shift of δ13C values in these Cenozoic fossils. Recent studies on the effect of atmospheric CO2 concentration/partial pressure (pCO2) on carbon isotope fractionations in C3 plants shed new lights toward a possible means to reconcile this long standing discrepancy. We test this hypothesis using these evolutionary conservative conifers from well-documented fossil lagerstätten deposited under humid climatic conditions against known environmental, climatic, and atmospheric conditions (including pCO2) reconstructed using various proxies. We believe that the combination of all these advantages from Cenozoic fossil lagerstätten provides an ideal material for testing the new method to infer the atmospheric CO2 concentration by using bulk and molecular carbon isotope data from C3 plants.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-287202

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