Figure 1: Geological setting of the bitumen clast in the Al Khlata Formation, upper Carboniferous, Oman.

(a) The bitumen clast in situ in Al Khlata Formation diamictite. (b) Location map of the Sultanate of Oman showing the bitumen clast locality (Wadi Al Khlata) in relation to the outcrop and subsurface extent of the Al Khlata, the likely source of the bitumen in the Thuraya area, and the ice flow direction as evidenced by glacially striated pavements. (c) Diagram showing our interpretation of the origin of the bitumen clast and its crustacean fragments. (d) Stratigraphy of the Al Khlata Formation showing the relative age of the deposits containing the bitumen clast. (e) Gas chromatogram of the solvent-soluble fraction of the bitumen clast. The chromatogram is unusual for a surface petroleum sample, as it contains a series of apparently unaltered n-alkanes in the range of nC7 to nC27. Biodegradation of surface oil seeps normally removes some or all of the n-alkanes present⁶⁰. The relatively high abundance of biomarker compounds eluting between 4,000 and 5,000 s is indicative of mixing of at least two oil charges from Huqf source rocks. Thermal maturity of the bitumen, estimated from molecular distributions of biomarker compounds and from bitumen reflectance analysis, suggests relatively low thermal maturity of the high-molecular-weight fraction (equivalent approximately 0.6% vitrinite reflectance).