To gain information on organic matter variability we analyzed 204 samples for total carbon (TC) and nitrogen (N), 190 samples for total organic carbon (TOC), 45 samples for stable carbon isotopes (δ13C), and determined the water content in 417 samples. We used an Elementar Vario EL III to estimate TC and N from two repeated measurements of each freeze-dried and milled sample. The measurement accuracy is 0.05% for TC and 0.1% for TN. We used a Vario MAX C analyser to determine TOC. Measurement accuracy was 0.1%. We analyzed δ13C from carbonate-freed samples using a Finnigan Delta-S mass spectrometer. Results are presented as δ13C values relative to the PDB reference standard (‰) with an error of ±0.15%.