Recent Conference Abstracts from our Research Group

A. Hope Jahren and Brian A. Schubert. 2011 AGU Meeting

"The Dependence of Plant δ13C on Atmospheric pCO2"

Numerous studies on multicellular plants have reported increasing carbon isotope fractionation with increasing concentrations of atmospheric carbon dioxide (pCO₂), but the magnitude of the effect is highly variable (i.e., 0.62 to 2.7 ‰ per 100 ppm CO₂). The majority of these experiments...(view/download pdf)

Daniel King, Brian Schubert, Katrina Foelber, and A. Hope Jahren. 2011 AGU Meeting

"Organismal versus Environmental Control of the Carbon Isotope Composition of Dicot Angiosperm Pollen: Implications for Paleoenvironmental Reconstruction"

The prevalence and diagenetic resilience of palynomorphs in Proterozoic and Phanerozoic sediments has led researchers to investigate its potential as an environmental proxy based on its stable isotope composition. Towards this, Loader and Hemming (2001), noted that the carbon isotope composition...(view/download pdf)

Brian A. Schubert, A. Hope Jahren, Jaelyn J. Eberle, Leonel S.L. Sternberg, Patrícia Ellsworth, David A. Eberth, and Arthur R. Sweet. 2011 AGU Meeting

"The Best Modern Analog for Eocene Arctic Forests is within Today's Korean Peninsula"

In the 25 years that have passed since the first extensive descriptions of the Fossil Forests that persisted above the Arctic Circle during the Eocene (~45-54 Ma), no less than four locations have been suggested as modern analogs. These locations represent a diverse collection of biomes and temperature/precipitation environments...(view/download pdf)

B.A. Schubert, A.H. Jahren, J.J. Eberle, L.S.L. Sternberg, D.A. Eberth, and A.R. Sweet. 2011 Geological Society of America Annual Meeting, Minneapolis, MN

"Wet summers in the Eocene Arctic quantified from high-resolution carbon isotope measurements across fossil tree-rings"

Discovery of exceptionally well-preserved fossil wood revealed that vast forests existed north of the Arctic Circle during the Eocene (~45-55 Ma). Recent estimates of mean annual paleoprecipitation, productivity, and relative humidity have led workers to characterize these forests as similar to today's temperate forests of the Pacific Northwest. Above the Arctic Circle, the extreme photoperiod limits...(view/download pdf)

A.H. Jahren, B.A. Schubert, L.S.L. Sternberg, and P. Ellsworth. 2011 Geological Society of America Annual Meeting, Minneapolis, MN

"A New Modern Analog for the Eocene Arctic Forests from Oxygen Isotopes in Cellulose-Derived Phenylglucosazone"

Several environmental parameters have been reconstructed for the Arctic forests of the Eocene, including mean annual temperature (MAT), mean annual precipitation (MAP), and relative humidity (RH). Based on these characteristics, a variety of locations have been proposed as modern analogs, including the Pacific Northwest, southeastern U.S., eastern Asia, and Chile. Here we report analysis of oxygen isotopes ...(view/download pdf)

Jahren, A.H. and Sternberg, L.S.L. 2011 Cretaceous-Paleogene Palaeoenvironments, Tectonics and Biostratigraphy of the Arctic and Subarctic, Tromsø, Norway (invited talk).

"Arctic Seasonal Patterns of Precipitation and Relative Humidity during the Middle Eocene (~45 Ma)"

Presently located in the far north of Canada, during the middle Eocene (~45 Ma) Axel Heiberg Island supported lush deciduous conifer forests, as did much of Earth's terrestrial landmasses north of the Arctic Circle. The spectacular preservation of middle Eocene wood allowed for intra-season sampling of stable oxygen and hydrogen in order to reconstruct the paleoseasonal environment of this Arctic forest of deciduous conifers. ...(view/download pdf)

Schubert, B.A. and Jahren, A.H. 2011 Cretaceous-Paleogene Palaeoenvironments, Tectonics and Biostratigraphy of the Arctic and Subarctic, Tromsø, Norway (invited talk).

"Early Eocene Arctic Seasonality Quantified from High-resolution, Intra-ring δ13C Analyses across Fossil Evergreen Wood"

High-resolution δ13C analyses across annual tree rings can be used to interpret deciduous versus evergreen strategies in modern and ancient specimens. The seasonal δ13C pattern seen in tree rings of deciduous species reflects a switchover from the use of isotopically heavy, stored-carbon to the use of isotopically light, actively photosynthesized carbon for the construction of new tissue, with climate being of secondary importance. ...(view/download pdf)

Jahren, A.H. and Schubert, B.A., 2010 AGU Fall Meeting

"Ultra-high Resolution Carbon Isotope Records in Tree Rings: Indicators of Carbon Allocation and Growing Season Precipitation/Temperature"

The rapidity and ease of carbon stable isotope measurements on organic substrates has opened the possibility of ultra-high resolution d13C analyses within tree rings at < 30 to 100 micron increments. We present such measurements for 80 individual tree rings, from 10 trees spanning the last 55 million years in age from arctic, temperate, and tropical environments... (view/download pdf)

Schubert, B.A. and Jahren, A.H., 2010 AGU Fall Meeting

"Total Summer Precipitation Estimated for the Early Eocene Arctic from High-Resolution Intra-ring Analyses of Fossil Wood"

During the Early Eocene (~53 – 54.5 Ma) Ellesmere Island was home to a forested ecosystem north of the Arctic Circle (ca. 76° N paleolatitude). Although several estimates exist for Eocene pCO₂ levels, temperature, and relative humidity in Arctic environments, quantitative estimates of precipitation have been elusive. We present here a new method for estimating mean-annual precipitation levels... (view/download pdf)

King, D.P., Foelber, K., Schubert, B.A., and Jahren, A.H., 2010 AGU Fall Meeting

"Potential of δ13C in Pollen to Serve as Paleotemperature Proxy"

Fossil pollen is an invaluable indicator of vegetation composition, is notably resilient against diagenetic alteration, and can be found in large quantities within highly chronologically-resolved substrates such as lake sediments. In addition, several recent isotopic techniques have made possible the analysis of small quantities (approaching <100 pollen grains)... (view/download pdf)

Hagopian, W.M. and Jahren, A.H., 2010 Fourth FIRMS Network Conference Abstract

"Reduction of Sample Size for Oxygen Isotope Analysis in Organic Compounds"

Early descriptions of "cryofocusing" - the controlled release of purified combustion products from a coldsink located directly upstream of the inlet to the mass spectrometer - promised a reduction in sample size to the 10-1000 nanomole range (Fry et al., 1996). While sample size is rarely limiting for most ecological and geological applications, reduction in sample size is a central issue in forensic analysis... (view/download pdf)

Hunsinger, G.B., Jahren, A.H. and Hagopian, W.M., 2010 Fourth FIRMS Network Conference Abstract

"An Off-Line Method to Eliminate Nitrogen-Oxide Interference for δ¹⁸O Analysis of Nitro-Organics"

Nitrogen-rich organic compounds, or nitro-organics, are of high importance to forensics in light of their use as explosive stimulants, detonators, or improvised explosive devices. Depending on the origin and processing all explosives acquire signatures amenable to isotopic discrimination... (go to reference | view/download pdf)