CHARACTERISATION OF ORGANIC MATTER FORMED IN HYPERSALINE CARBONATE/EVAPORITE ENVIRONMENTS: HYDROCARBON POTENTIAL AND BIOMARKERS OBTAINED THROUGH ARTIFICIAL MATURATION STUDIES

Sediments deposited under hypersaline conditions, particularly those laid down in the transition zone between marine carbonates and evaporites, are increasingly recognised as a potential source for oil. Recent environments that lie in waters with elevated salinities are sites of very high biological productivity that can be used as models for evaporite-related sedimentation in the geological record. Of particular importance is the range of elevated salinities well above the range for normal marine biota, in which organic-rich cyanobacterial carbonates form and accumulate in large quantities. Such organic matter collected from a number of modern evaporative settings has been examined in terms of oil potential and for biomarkers characteristic of hypersaline environments. The regions studied include marine-fed salinas (Santa Pola, Spain); marine-fed sabkhas (Abu Dhabi, UAE); and continental ponds and lakes (La Mancha region, Spain). High values of H/C ratio and HI demonstrate the oil source potential of this organic matter. The hydrocarbons generated during artificial maturation of these immature sediments resemble those naturally occurring in ancient petroleum-generating evaporitic systems. Variations in the total