Sedimentology, depositional settings and organic geochemistry in the southern part of the South Caspian Basin

In order to study sedimentology, depositional settings and organic geochemistry in the southern part of the South Caspian Basin, 124 surface samples were taken from shallow to deep water with utilizing Van Veen Grab. All samples were analyzed for total organic carbon (TOC), S2 (Rock-Eval Pyrolysis), biota content (bioturbating organisms), particles size and mineralogy. Based on shallow seismic data, a range of depositional settings were distinguished including delta, shelf, slope, and basin plain. Composition of samples revealed detrital particles (quartz, feldspar, muscovite, carbonate and non-carbonate rock fragments and clay minerals (illite, chlorite, kaolinite, smectite)), as well as organic/biogenic components (i.e. bivalves, gastropods, ostracods) and non-skeletal particles (i.e. mud peloids). Several factors (e.g. TOC, organic matter type, biota content) suggest that these sediments were deposited under markedly different redox conditions, namely: (1) shelf and slope settings (oxic sediments), (2) basin plain settings (dysoxic sediments). The dysoxic sediments are enriched in type II organic matter (OM) with high TOC content (>1wt. %) while the oxidized sediments are enriched in infaunal organisms (i.e. ostracods and gastropods), and contain type III OM with low TOC content (