HR: 1340h
AN: PP23B-1348    [Abstracts]
TI: Using Apatitic Conodont Oxygen Isotopic Values to Determine the Cause of Late Ordovician Third-Order Stratigraphic Sequences
AU: * Tyra, T A
EM: matyra@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences, MSCO3-2040, 1 University of New Mexico, Albuqueque, NM 87131, United States
AU: Maya, E
EM: dolomite@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences, MSCO3-2040, 1 University of New Mexico, Albuqueque, NM 87131, United States
AU: Atudorei, V
EM: atudorei@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences, MSCO3-2040, 1 University of New Mexico, Albuqueque, NM 87131, United States
AU: Stephen, L A
EM: lesliesa@jmu.edu
AF: James Madison University, Geology and Environmental Science, James Madison University, MSC 6903, Harrisonburg, VA 22807, United States
AB: Recent work suggests a link between third-order (~1-5 Myr) sea-level fluctuations and climate change, even in greenhouse periods. Upper Ordovician third-order transgressive-regressive sequences are pervasive in the stratigraphic record, can be correlated worldwide (i.e. North America, Baltica, China), and ambiguous in cause. We are evaluating climate's role in third-order sea-level change by analyzing the δ¹⁸O of conodont apatite, which is a proxy for both glacio-eustasy and paleotemperature. Conodont phosphatic oxygen is a more robust repository of primary oxygen isotope values than more extensively-studied calcareous fossils, which have been extensively studied. If sea-level change is climatically-driven (glacio-eustasy and thermo-eustasy), δ¹⁸O values will decrease with sea-level rise and increase with sea-level fall. We report preliminary results from Upper Ordovician sequences in the Monitor Range of central Nevada. The six stratigraphic sequences (30m-95m thick) preserve basinal-to-outer-shelf carbonates with the youngest sequence representing the Hirnantian glaciation. We collected conodont samples at a 2-10m resolution and also determined bulk carbonate δ¹³C for additional chemostratigraphy. With this information, we hope to determine if glacio-eustasy has a role within the five pre-Hirnantian sequences.
DE: 1030 Geochemical cycles (0330)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1051 Sedimentary geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting