HR: 10:20h
AN: PP42A-01 INVITED     [Abstracts]
TI: Molecular Proxy Approaches for Paleohydrology
AU: * Freeman, K H
EM: kate@essc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Smith, F A
EM: fsmith@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Polissar, P
EM: ppolissa@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Turich, C H
EM: cturich@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Pedentchouk, N
EM: nikolai.pedentchouk@yale.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Pedentchouk, N
EM: nikolai.pedentchouk@yale.edu
AF: Yale University, Department of Geology and Geophysics, New Haven, CT 06511 United States
AB: There is a rich assembly of isotopic and mineral indicators for paleohydrologic properties of ancient environments. Commonly employed examples include mineral abundance ratios and the isotopic signatures of minerals and macromolecular organic phases such as cellulose. Preservation of these materials can be influenced strongly by natural processes in the environment, most notably resulting in the alteration or loss of carbonate mineral isotopic signatures. In order to expand our ability to document paleoclimatic conditions in continental environments, additional tools for both aquatic and terrestrial settings are in development based on the hydrogen isotopic signatures of individual lipids from microbes, algae and vascular plants. Plant leaf waxes (long-chain n-alkanes) preserve well in soils and aquatic sediments. Deuterium signatures in ancient leaf lipids potentially record isotopic properties of ancient plant water, reflecting isotopic signatures of rainfall and soil waters as well as the level of relative humidity. We have studied grasses, trees and other plant types from both greenhouse and field localities in order to understand the relative influences of plant physiology, physiognomy,and growth conditions (humidity) on lipids as recorders of plant water isotopic signatures. Submerged aquatic algae are not directly influenced by humidity, and recent work has shown their biomarkers to be promising paleolimnological proxies. We will discuss the potential for algal compounds as recorders of waters in modern high altitude sites and for ancient paleoaltimetry applications. Recent theoretical considerations in conjunction with analyses of lipids from ancient sediments point to the limitation of the preservation of paleohydrologic signatures set by thermal maturation approaching oil-generating conditions.
DE: 3344 Paleoclimatology
DE: 1040 Isotopic composition/chemistry
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting