29 th International Meeting on Organic Geochemistry (IMOG) 1–6 September 2019, Gothenburg, Sweden ORGANOFACIES VARIATION CONTROL ON HYDROCARBONS AND NON- HYDROCARBONS FROM THE AUSTRIAN MOLASSE BASIN AS REVEALED BY FTICR-MS S.H. Hosseini 1 , M. Brown 1 , R. Snowdon 1 , R.F. Sachsenhofer 2 , T.B.P. Oldenburg 1 1 University of Calgary, Canada, 2 Montanuniversität, Leoben, Austria The North Alpine Foreland Basin, also called Molasse Basin, is a peripheral foreland basin in central Europe and extends from France to the eastern border of Austria. The Austrian sector is the most petroliferous region of the basin with hydrocarbon reservoirs of thermogenic and microbial origin. Lower Oligocene fine-grained sedimentary units, the Schöneck Formation and the overlying Dynow and Eggerding Formations, are organic-rich and considered to be the main potential source rocks for thermogenic hydrocarbons. Literature review revealed that there are two oil families, a western type “A” and an eastern type “B”, which is most likely attributed to differences in organic facies of the respective source unit(s) (e.g. Gratzer et al., 2011). In this study organofacies variations of the potential source units and crude oils from the Molasse Basin are investigated using conventional and advanced analytical techniques such as Gas Chromatography - Mass Spectrometry (GC-MS) and Fourier transform ion cyclotron resonance-mass spectrometry (FTICR-MS) in three different ionization modes (APPI-P, ESI- N, ESI-P, see Oldenburg et al., 2014 for details). Sixteen crude oils as well as sixteen samples of potential source rocks have been characterized in detail. According to our results, the investigated crude oils can be classified in three groups: type A, type B and biodegraded oils. Considering gas chromatogram patterns, both type A and B oils show close similarities in terms of n-alkane distributions, pointing to common source(s) for both oil families. APPI-P analysis revealed that the HC class is most abundant in both oil types, though the eastern oils (type B) are relatively more enriched (80-82%) compared to the western oils (73-79%). The acidic composition, measured with electrospray ionization in negative ion mode (ESI-N), is dominated by nitrogen only (Ny; y=1,2) compound classes with higher relative abundances detected in the oils from the western type A (51-68%) compared to the eastern type B oils (33-47%). The western oils are enriched in Ox classes. Moreover, molecular parameters such as DBT/P ratios, Ts/(Ts+Tm) ratios as well as C35/C34 homohopane ratios can be used for grouping the investigated oils. However, based on maturity-sensitive parameters both oil families display more or less the same maturation levels. Also, they show no evidence for biodegradation. Thus, the observed differences between the two oil groups is most likely attributed to source facies changes within the source unit(s). In addition to the crude oils, their potential source rocks were investigated. These source rock samples are immature (Tmax range: 408-427 ° C) except for the redeposited sediments of Lower Oligocene succession which is called “Oberhofen facies” (Tmax range: 436-445 ° C) (Schulz et al., 2002). Since the Molasse Basin is a foreland basin, the source units are normally immature toward the northern basin slope and mature source rocks can be find only beneath the Alpine nappes. Source-related biomarkers such as steranes and hopanes distributions (Fig. 1) pointing to the oxic state of the depositional environment from marine to brackish, that is shown to be induced by the basin subsidence/uplift and water level changes (Schulz et al., 2002). According to our data it is evident that oxygen-containing compounds such as Ox, OxNy and OxSz classes are predominant in the ESI-N-sensitive portion of all source intervals (see the embedded pie