Abstract Rock–Eval 6 analysis, a well established screening tool for petroleum geochemistry, is being increasingly used to characterise the varying species of organic matter (OM) in the bulk samples of recent aquatic sediments. This is particularly important due to recent scientific attention on the role of OM in biogeochemical distribution of environmentally hazardous compounds (e.g., trace metals) in recent sediment archives. Rock–Eval’s automated use, low sample volume requirements and its high analytical accuracy and precision makes it an ideal tool for relatively rapid screening of OM in sediment cores. However, to date, there has been no broad scale standardisation to determine what may be contributing to each signal (e.g., S1, S2, S3, RC). We have selected a wide variety of representative, pure biochemicals (proteins, lipids, carbohydrates and lignins) and biological standards (phytoplankton, copepods, tree bark and conifer needles) to better understand the Rock–Eval 6’s measured organic matter parameters in the unconventional environmental samples. These data have been corroborated with organic petrographical and elemental (CHNS/O) data. Our results show that small organic molecules ( 2 ratios: OICO, OICO 2 and OIRE6) are the best discriminants for the source of OM. Finally, step wise pyrolysis of biological standards coupled with elemental analysis (CHNS/O) suggests that S2 and, to a lesser extent, S3 (S3CO and/or S3CO 2 ), would be most responsible for metal-binding elements such as S and N, with implications for element biogeochemical cycles.