MITAS 2009 CHN and Carbon Isotope Data

METHODS

CHN Elemental Analysis: Sample preparation and analytical methods for the Total Organic Carbon (TOC), Total Nitrogen (TN), and Inorganic Carbon (IC) data shown here are described in Phillips et al. (2011). For the MITAS CHN data set, approximately 1 cm3 of bulk sediment was collected from selected downcore depths in the sediment cores and used for both CHN measurement on the Perkin Elmer 2400 Series II CHNS Elemental Analyzer in the Department of Earth Sciences at UNH and carbon isotopes measured at the UNH Stable Isotope Lab (described below). For the analyses presented here, we have used the CHNS analyzer to measure Total Carbon (TC) and TN first and then the TOC, after acidification with sulfurous acid. IC values are calculated by difference, where IC = TC-TOC. Duplicate measurements were made approximately every 10 samples as run through the CHN Analyzer. Values shown for TOC, TN, and IC, include a 2 sigma range for the replicates. CaCO3 is calculated using the formula weight assuming all of the IC measured in the sample exists as calcium carbonate. The TOC/TN is provided as a first order proxy for the source of the organic matter.

Phillips, S.C., Johnson, J.E., Miranda, E., Disenhof, C., 2011, Improving CHN measurements in carbonate-rich marine sediments. Limnology and Oceanography: Methods, vol 9, pp. 194-203, DOI 10:4319/lom.2011.9.194.

Carbon Isotopes: Sample preparation and analytical methods for the organic carbon isotope measurements include the following. Acidification of bulk sediment samples from the cores using sulfurous acid to remove any CaCO3 components. The residual, CaCO3-free, bulk sediment sample was then measured in the UNH Stable Isotope Laboratory using a Thermo Finnegan DeltaPlus isotope ratio mass spectrometer (IR-MS) interfaced with a Conflo III interface system to a Costech ECS 4010 Elemental Analyzer. Organic carbon from the sample was combusted in the elemental analyzer and the resulting CO2 was pumped to the IR-MS where 13C and 12C were separated and measured. Peak areas of 13C and 12C were used to calculate isotope ratios with respect to the Pee Dee Belemnite (PDB) reference standard for calculations of the δ13C values reported in the data table. The δ13C values when paired with the TOC/TN provide a robust indication of the organic matter source. Similar to the CHN measurements, duplicate samples were run approximately every 10 samples and reported as a mean with a 2 sigma range. CONTACT Joel E. Johnson, Associate Professor University of New Hampshire Department of Earth Sciences 56 College Rd. James Hall 214 Durham, NH 03824 joel.johnson@unh.edu