The marine fossil record contains a myriad of organic molecules, which derive from marine (algae, (cyano)bacteria, archae) and terrestrial organisms living at the time of deposition. These so-called biomarkers contain information which, if properly decoded, can give insight in past climatic and palaeo-environmental changes. This can help in (i) understanding natural and anthropogenic influences on present-day climates and depositional systems, and (ii) deciphering the conditions which have led to sequestration of organic carbon in the geological record, and thus to the formation of marine petroleum source rocks. Sedimentary
organic components are derived from biochemicals of primary producers and organisms processing primary produced carbon.

On a molecular level three different features of biochemicals can be discriminated: (i) the carbon skeleton, (ii) functional group(s), (iii) stable carbon isotopic composition. If these three types of information are fully preserved in sedimentary biomarker counterparts the most accurate palaeodepositional reconstruction can be obtained. However, a wide range
of microbial and (physico)chemical processes during settling of the detritus to the sediment and during subsequent burial of the sediment affect biochemicals. Therefore, molecular biogeochemists have to unravel the diagenetic and catagenetic processes which alter the structures of primary biochemicals in order to properly decode the sedimentary record.
A very important process in this respect is reaction of reduced inorganic sulfur species with organic molecules during early diagenesis which leads to sequestration of biochemicals in complex sulfur-rich macromolecular aggregates.

The structural identification and quantitation of sedimentary biomarkers, the determination of their 13C content, the unravelling of their origin through understanding of their diagenetic pathway of formation, and the application of concentrations and 13C contents of biomarkers to trace changes in past depositional systems are all topics of prime interest in my research.

The structure, properties and origin of the major form of organic carbon in the geosphere, kerogen, is a second item of major interest. Kerogen is defined as the fraction of organic matter insoluble in common organic solvents and typically represent >90% of the total organic matter in immature sediments. Kerogen is the major precursor of petroleum and its
properties determine the timing of petroleum generation during burial of kerogen in the subsurface and the quality of the petroleum formed. However, the origin and chemical structure of kerogen are still a matter of debate and my research aims to solve these questions.