DOI: 10.1594/pangaea.933277
title: Compound-specific carbon isotope results from the SH#1 core analyzed and processed at University of Colorado Boulder

description: This data set was used to trace changes in carbon cycling and productivity in the Western Interior Seaway (WIS) through Oceanic Anoxic Event 2 (OAE2; 94 Ma). Samples were present in the SH#1 core, which was recovered in the summer of 2014 near Big Water, Utah (37.158466°N, 111.531947°W). Compound-specific carbon isotope data was produced using gas chromatography-isotope ratio mass spectrometry (GCIRMS) between February 2017 and November 2018. Raw data were used in calculations described in Boudinot et al., (in review) to estimate changes in the carbon isotopic composition of marine DIC and atmospheric CO2, as well as changes in pCO2, throughout OAE2, all of which are outlined in the data file. Assumptions and estimates of environmental conditions impacting these estimated carbon-cycle relevant metrics are presented. These data demonstrate both the methods and outputs of using compound-specific carbon isotope analyses to estimate local and global carbon cycle dynamics during an interval of global change during Earth history. Specifically, the data file includes (A) core depth in meters of the SH#1 core, (B) the name of the compound identified using GC-MS (in Boudinot et al., 2020, Neritic ecosystem response to Oceanic Anoxic Event 2 in the Cretaceous Western Interior Seaway, USA. Palaeogeography, Palaeoclimatology, Palaeoecology, 546, 109673), (C) the calibrated mean carbon isotopic composition of the compound in per mil relative to VPDB, (D) the preparation undertaken prior to analysis on GC-IRMS (i.e., either having undergone urea adduction or not), (E) the carbon isotopic composition of carbonate from the same depth as presented in Jones et al. (2019, Astronomical pacing of relative sea level during Oceanic Anoxic Event 2: Preliminary studies of the expanded SH#1 core, Utah, USA. GSA Bulletin, 131 (9-10): 1702–1722) or as analyzed in Boudinot et al. (in review) (described in methods, indicated in figures), (F) the analytical standard deviation of the carbon isotopic composition of compounds based on either duplicate analysis, or on the predicted standard error based on the calibration ("true_d13c_pred_se" in isoprocessor), (G) the number of duplicate compound-specific analyses, with NA indicating that only one analysis was performed and thus the predicted standard error based on the calibration was used to estimate the standard deviation, (H-I) the minimum and maximum net carbon isotope fractionation during carbon fixation and biosynthesis for the autotroph responsible for each lipid synthesis, in per mil, (J-L) the minimum, maximum, and average fixed inorganic carbon pool carbon isotopic composition estimated using the equations presented in Boudinot et al. (in review), (M) temperature estimate in degrees kelvin, (N) the calculated temperature-dependent carbon isotope fractionation of CO2 with respect to bicarbonate in per mil, (O) the carbon isotopic composition of marine DIC based on the carbon isotopic composition of carbonate for that depth in per mil, (P-R) the minimum, maximum, and average carbon isotopic composition of primary photosynthate calculated using the equation described in Boudinot et al. (in review) in per mil, (S) the carbon isotopic fractionation associated with photosynthesis in per mil, (T) the solubility constant of CO2 based on salinity and temperature estimates relevant to the SH#1 core, (U-V) the high and low b-value estimates used as constants to represent the role of productivity in modulating carbon isotope fractionation during photosynthesis, (W) the carbon isotopic composition of aqueous CO2 estimated using the carbon isotopic composition of carbonate, (X) the carbon isotopic composition of aqueous CO2 estimated using the carbon isotopic composition of biomarkers, (Y) epsilon p estimated using b values, the calculated carbon isotopic composition of primary photosynthate, and the calculated carbon isotopic composition of aqueous CO2 estimated using carbonate, (Z-AA) the high and low estimates of the aqueous concentration of CO2 in seawater at the SH#1 core location using epsilon p estimates from the carbon isotopic composition of carbonate, in micromol CO2/kg, (AB-AC) the high and low estimates of pCO2 using the estimate of aqueous CO2 derived from the carbon isotopic composition of carbonate, in ppmv, (AD) epsilon p estimated using b values, the calculated carbon isotopic composition of primary photosynthate, and the calculated carbon isotopic composition of aqueous CO2 estimated using biomarkers, (AE-AF) the high and low estimates of the aqueous concentration of CO2 in seawater at the SH#1 core location using epsilon p estimates from the carbon isotopic composition of biomarkers, in micromol CO2/kg, and (AG-AH) the high and low estimates of pCO2 using the estimate of aqueous CO2 derived from the carbon isotopic composition of biomarkers, in ppmv.