HR: 1340h
AN: PP43B-1253    [Abstracts]
TI: Mid-Pleistocene Lacustrine Records of Carbon and Nitrogen Elemental and Isotopic data from Valles Caldera, New Mexico, USA
AU: * Cisneros-Dozal, L
EM: cisnerosd@lanl.gov
AF: Los Alamos National Laboratory, Earth & Environmental Sciences Division Hydrology, Geochemistry & Geology Group, Los Alamos, NM 87545, United States
AU: Heikoop, J
EM: jheikoop@lanl.gov
AF: Los Alamos National Laboratory, Earth & Environmental Sciences Division Hydrology, Geochemistry & Geology Group, Los Alamos, NM 87545, United States
AU: Fessenden, J
EM: julianna@lanl.gov
AF: Los Alamos National Laboratory, Earth & Environmental Sciences Division Hydrology, Geochemistry & Geology Group, Los Alamos, NM 87545, United States
AU: Fawcett, P
EM: fawcett@unm.edu
AF: University of New Mexico, Department of Earth & Planetary Sciences, Albuquerque, NM 87131, United States
AU: Kawka, O
EM: kawkaoe@U.WASHINGTON.EDU
AF: University of Washington, School of Oceanography, Seattle, WA 98195, United States
AU: Sachs, J
EM: jsachs@u.washington.edu
AF: University of Washington, School of Oceanography, Seattle, WA 98195, United States
AB: Lacustrine deposits dating back to the middle Pleistocene were recovered from Valles Caldera, located in Northern New Mexico. The core (82 m long) contained ~75 meters of lacustrine sediments. The age of the sediments was constrained by Ar-Ar dating of a primary tephra layer from the base of the core, in combination with correlation to the deep-sea marine isotope stage record along the length of the core. The lacustrine sediments span from ~350 k YBP to 552 k YBP covering two glacial-interglacial stages, from MIS 11 to MIS 14 and part of MIS 10. Total organic carbon (TOC) in the siderite free fraction (i.e. diagenetic siderite was chemically removed) ranged from <1% to 7% with the lowest values predominantly observed during glacial times and marked increases at the onset of interglacials. Particularly high TOC is observed during the long interglacial MIS 11. C/N ratios ranged from values of <2 to ~11 with lowest values in general observed during glacial times indicating increased input from aquatic sources and suggesting deepening of the lake as a result of wetter glacial climate. δ¹³C values measured in the siderite free fraction, ranged from -28‰ to -20‰ and remained more negative overall during glacial times. We are currently working on D/H analyses of leaf lipid biomarkers which may provide insight into the delivery of meteoric water to the region during these climatic stages, i.e. relative contributions of summer monsoonal (from the Gulfs of Mexico and California) vs. winter frontal precipitation (from the North Pacific).
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1051 Sedimentary geochemistry
DE: 4926 Glacial
DE: 4936 Interglacial
DE: 4940 Isotopic stage
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting