Paper No. 112-5
Presentation Time: 8:00 AM-5:30 PM
ASSESSING EARLY LAND PLANT IMPACTS ON THE EVOLVING PALEOZOIC MARINE BIOSPHERE
WINTERS, Ginny, Earth and Planetary Sciences, University of California Riverside, 900 University Ave, Riverside, CA 92521, SPERLING, Erik A., Department of Earth and Planetary Sciences, Stanford University, 450 Jane Stanford Way, Stanford, CA 94305, ELLEFSON, Emily, Department of Earth and Planetary Sciences, Stanford University, Stanford, CA 94305, TARHAN, Lidya, Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511, MELCHIN, Michael, Department of Earth Sciences, St. Francis Xavier University, Antigonish, NS B2G 2V5, Canada, DEWING, Keith, Geological Survey of Canada, Calgary, AB T2L, Canada and LOVE, Gordon, Department of Earth and Planetary Science, University of California, Riverside, 900 University Ave., Riverside, CA 92521
The Late Ordovician-Devonian transition was a critical interval of environmental and ecological change, with the radiation and diversification of early land plants and changes in marine carbon and nutrient cycling contributing to a major protracted change in the global biosphere. The emergence of early land plants may have contributed to a rise in atmospheric oxygen during the Paleozoic Era, alongside a hypothesized flux of terrestrial organic carbon and marine delivered nutrients, which could have significantly perturbed marine carbon and other biogeochemical cycles. However, the magnitude, timing, and global influence of this terrestrial chemical flux on climate, ocean chemistry and biological productivity remains poorly constrained. Notably, Late Ordovician-Silurian-Devonian lipid biomarker records tracking the rise of terrestrial carbon input into the marine realm are sparse.
An extensive set of thermally well-preserved Paleozoic sedimentary rocks from Bathurst Island, Arctic Canada, and from Alaska, were collected and are undergoing a detailed organic geochemical investigation to determine: i) early plant lipid contributions to ancient marine organic matter, and ii) changes in marine primary productivity for Ordovician, Silurian and Devonian shelf/slope settings in these locations. Increasing land plant input to ancient sedimentary organic matter may be recorded as an increase in the relative and absolute abundances of waxy n-alkanes (C23-C33) and/or plant (bryophytes and early tracheophytes) terpenoids. Secular changes in marine phytoplankton compositions have been recognized in our study by the distribution of steroid, hopanoid and other terpenoids using selective multiple reaction monitoring (MRM)-gas chromatography-mass spectrometry. Our investigation will help better constrain the composition of marine communities through the Late Ordovician-Devonian transition and help untangle the cryptic influence of progressive continental greening in perturbing the Paleozoic marine biosphere.
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