Lipid biomarker analyses (alkanes, sterols and fatty acids) of authigenic carbonates collected on the FK190612 research expedition in the north Pacific Ocean in June and July 2019 along the Cascadia Margin.

PLANT BIOMARKER CONCENTRATIONS (N-ALKANES, STEROLS, FATTY ACIDS): The biomarker composition of the authigenic carbonate rocks was determined by gas chromatography–mass spectrometry (GC–MS) at the USGS Organic Geochemistry laboratory in Santa Cruz, California. The samples were extracted using a Dionex ASE with a mixture of dichloromethane and methanol (9:1;v:v) and acetone: hexane (1:1;v:v). Prior to extraction, internal standards were added (5-alpha androstane and 5 alpha-androstan-3-beta-ol). The lipid extracts were passed though glass funnels containing sodium sulfate to remove excess water, followed by separation into compound classes by silica gel column chromatography (silica gel 60). The following fractions were eluted: (1) F1-hydrocarbons (100 percent n-hexane), (2) F2-aromatics (50 percent toluene: hexane), (3)F3- alcohols, ketones (20 percent ethyl acetate: hexane), and, F4 (40 percent ethyl acetate:hexane). The alcohol fraction was converted to trimethylsiloxyl derivatives by bis (trimethylsilyl) trifluoroacetamide (BSTFA with 1 percent TMCS) heated at 60 degrees C for 1 hour followed by evaporation to remove derivatizing chemicals and brought up to a final volume of 500 microliter with Optima hexane prior to GC–MS analysis. Extracts were analyzed by splitless injection onto an Agilent 8890 gas chromatograph interfaced to an Agilent 7000D triple quad mass spectrometer. The gas chromatograph oven program had an initial temperature of 90 degrees C for 4.0 minutes then ramped up to a final temperature of 310 degrees C for 10 minutes. The capillary column (alkanes and sterols: DB-5MS: 30 meter length, 0.25 millimeter id with a 25 micron phase thickness) was directly interfaced to the ion source of the mass spectrometer. Hexane instrument blanks, extraction blanks, and procedural sample duplicates were run and analyzed every 10 samples. 5- and 6- point calibration curves (fatty alcohols/sterols and n-alkanes, respectively) were analyzed and used for calculating concentrations. Compound identification was through individual standard spectra (when available), published reference spectra and by relative retention times and elution order. Concentrations of individual lipids were determined based on peak area in relation to internal and external standards; reported concentrations are blank corrected and normalized to both dry weight and percent organic carbon.