HR: 0800h
AN: PP51B-1335    [Abstracts]
TI: Cretaceous records of atmospheric CO$_{2}$ from fossil conifers
AU: * Llorens, L
EM: l.llorens@sheffield.ac.uk
AF: The University of Sheffield, Dept. Animal and Plant Sciences, Western Bank, Sheffield, S10 2TN United Kingdom
AU: Gomez, B
EM: benard@earth.leeds.ac.uk
AF: The University of Leeds, School of Earth Sciences, Leeds, LS2 9JT United Kingdom
AU: Daviero-Gomez, V
EM: daviero@univ-lyon1.fr
AF: Universite Claude Bernard, UMR 5125 Lyon, Villeurbanne, 69622 France
AU: Beerling, D
EM: d.j.beerling@sheffield.ac.uk
AF: The University of Sheffield, Dept. Animal and Plant Sciences, Western Bank, Sheffield, S10 2TN United Kingdom
AB: Experimental studies indicate the stomatal characteristics of conifer shoots, like angiosperm leaves, are sensitive to changes in the global atmospheric CO$_{2}$ concentration. Consequently, fossil conifers may serve as valuable archives of pre-Quaternary paleo-CO$_{2}$ information, complementing that of other proxies and geochemical models of the long-term carbon cycle. Our study investigated this possibility by focussing on the fossil genus {\it Frenelopsis}, which has robust, degradation resistant cuticles and a continuous stratigraphic record throughout most of the Cretaceous. We measured the stomatal index (proportion of epidermal cells that are stomata) of {\it Frenelopsis} cuticles from eight Western European localities dating from Late Barremian to Late Cenomanian (131 to 90 Ma). Calibrating the record using nearest-living equivalent species indicated atmospheric CO$_{2}$ levels of 1000-1200 p.p.m.v. during the Barremian/Aptian and lower values of 500-1000 p.p.m.v. during the Albian and Cenomanian. The results are in general agreement with earlier CO$_{2}$ estimates from paleosols and phytoplankton and suggest quite large variations in atmospheric CO$_{2}$ took place during the Cretaceous, some of which may be linked with short-lived cooling events revealed by high resolution oxygen isotope studies of marine sediments.
DE: 3344 Paleoclimatology
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting