2006 Annual Science Report
Pennsylvania State University Reporting | JUL 2005 – JUN 2006
Evolution of a Habitable Planet (Arthur)
1) Permian-Triassic Events: We have submitted two manuscripts on the Permian/Triassic boundary event with graduate student Tony Riccardi, which are now accepted for publication. The first (Palaeogeography, Palaeoclimatology, Palaeoecology) discusses patterns in δ13C (δ13Ccarbonate-δ13Corganic) across the Permian-Triassic boundary, and the second (Geochimica et Cosmochimica Acta) interprets changes in oceanic sulfur isotopes of sulfate and sulfide in terms of CUEs (chemocline upward excursions) in a followup to the hypothesis put forth by Kump, Pavlov and Arthur (2005). T. Riccardi also collected samples in the past year from two other Permian-Triassic sections in Turkey, along with (then Penn State Post-Doc) Jon Payne (Stanford), Dan Lehrman (University of Wisconsin-Oshkosh) and his student Meg Siebel, and Demir Altiner (Middle East Technical University). A large number of samples were collected and are being processed at present for sulfur isotope investigations.
2) Nitrogen Cycling at Chemoclines: We have investigated nitrogen isotope systematics in modern anaerobic environments and at oxic/anoxic interfaces using the modern Black Sea and Fayetteville-Green Lake as environments for establishing the relative importance of water-column processes (nitrogen fixation, ammonia and nitrate assimilation, denitrification) as determinants of particulate N fluxes to sediments and their N isotopic values. We (graduate student Jamie Fulton) have expended considerable effort in developing a new method for analyzing nanomolar quantities of organic material for carbon and nitrogen isotopes. We will now be able to analyze individual pigment fractions to document the effects of diagenesis. In addition we (graduate student Chris Junium) have analyzed black shales deposited in ancient anoxic marine basins (Neoproterozoic, Cretaceous, Devonian) for comparison. Ultimately, we hope to demonstrate the fidelity of sedimentary nitrogen as a record of nitrogen cycling in ancient environments for application to interpreting Precambrian paleo-nutrient cycles. Thus far it appears that nitrogen fixation is an important process in black-shale forming environments; most black shales have nitrogen isotope values near 0 permil. We have submitted a manuscript on the Cretaceous work (Geosystems, Gechemistry, Geophysics).
PROJECT MEMBERS:Katherine Freeman
RELATED OBJECTIVES:Objective 4.1
Earth's early biosphere
Biochemical adaptation to extreme environments
Environmental changes and the cycling of elements by the biota, communities, and ecosystems