Total organic carbon (TOC) and δ13CTOC measurement from drillhole FB2001 located in Messel (Darmstadt)

The methodology for total organic carbon (TOC) and δ13CTOC measurement followed Bauersachs et al. (2014, doi:10.1016/j.palaeo.2014.06.015). In brief, for TOC concentrations, sediment samples (approximately 30 mg) were dried and powdered, pretreated with excess 2M hydrochloric acid (HCl) to eliminate carbonates, neutralized with distilled water, and dried at 50°C for 24 hours. Subsequently, samples were analyzed in duplicates using a CS-Analyser 144DR (Leco Corporation) at the Institute of Earth Sciences at Heidelberg University, with a sample reproducibility of less than 0.5%. For δ13C analysis, portions of the powdered, decalcified sediment samples (1-2 mg) were examined using a Flash Elemental Analyzer 1112 (Thermo Scientific), connected to the continuous flow inlet system of a MAT 253 gas source mass spectrometer (Thermo Scientific) at the Institute of Geosciences, Goethe University Frankfurt. Carbon isotopes in graphite standard USGS24 were analyzed alongside the samples to ensure accuracy and precision. Isotope ratios are expressed in conventional delta notation: δsample (‰) = [(Rsample − Rstandard) / Rstandard - 1] × 1000, where R represents the ratio of 13C/12C of the sample and the standard Vienna Pee Dee Belemnite (VPDB). Accuracy and precision of all isotopic analyses were determined by replicate sample analysis, yielding pooled standard errors better than 0.2 ‰ for δ13CTOC.