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Abstract Detail

Paleobotanical Section

Yang, Hong [1], Leng, Qin [2].

Molecular carbon and hydrogen isotope compositions from Cenozoic conifers: Physiological and paleoclimatic interpretations.

Measurement of both molecular carbon and hydrogen isotopic compositions of leaf wax from plant fossil compressions holds great potential as a powerful tool to study physiology of ancient plants, adding unique information for paleoclimatic interpretation. Our recent work on some well-preserved Cenozoic conifers such as Metasequoia, Glyptostrobus, Taxodium, Larix, and Pseudolarix from a number of North American sites has demonstrated that genus-specific molecular carbon and hydrogen isotope signals of in situ n-alkanes from these conifers present a rare opportunity to elucidate plant physiological response to ancient atmospheric and hydrological changes during Cenozoic. A critical step to apply plant hydrogen isotope data to paleoclimatic interpretation is to determine apparent hydrogen isotope fractionations (ε) between plants and environmental water. Coupled with greenhouse experiments using three living deciduous conifers, Metasequoia glyptostroboides, Taxodium distichum, and Larix laricina, whose fossil counterparts were common components of Paleogene Arctic floras, we demonstrated that the physiological effect of low intensity continuous light, e.g., during High Arctic summer, on plant hydrogen isotope signals results in up to 40 positive hydrogen isotope shift in leaf n-alkanes under continuous light conditions in comparison with that under diurnal light conditions. This effect, largely due to 24-hour leaf transpiration, is taxon-specific. The experimentally determined apparent hydrogen isotope fractionations between source water and individual lipids (εlipid -water) can be applied to fossil materials to calculate hydrogen isotope values of ancient precipitation at high latitudes using deciduous fossil conifers found in the Arctic area. Such data allow us to assess high-latitude moisture transportation which played important role in global paleoclimate during Cenozoic warming periods.

Broader Impacts:

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1 - Bryant University, Science and Technology, College of Arts and Sciences, Smithfield, RI, 02917, USA
2 - Bryant University, Science and Technology, College of Arts and Sciences, 1150 Douglas Pike, Smithfield, RI, 02917, USA

stable isotope

Presentation Type: Oral Paper:Papers for Sections
Session: 58
Location: 556A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 2:15 PM
Number: 58004
Abstract ID:471


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