Biological marker geochemistry of selected oils and possible source rocks from central Alborz Basin

Surface oil seeps from Alasht, Lapur and Jenesem share many compositional affinities including distributions and concentrations ofnormal alkanes, terpanes and steranes. These oils also show many similarities with that of Jurassic sediments (Shemshak Group, KlarizFormation) systematically sampled from the Galandrud Coal Mine. Recent geochemical studies in this area indicated that theShemshak Group is rich in organic matter and has potential to generate oil and chiefly gas. The Kalariz Formation here is composed of350 m of mudstones, siltstones and fine-grained sandstones with over 30 coal seams. This formation is thought to have sourced Alashtand Lapur oil seeps. GC and GC-MS chromatograms of Jenesem oil are unique and show no any similarities with that of abovementioned oils or the Shemshak Formation. This indicates that the Jenesem oil has been generated from a different source rock but itsorigin is still unknown.