Catagenesis of Organic Matter and Petroleum Potential of Proterozoic and Phanerozoic Deposits of the Anabar–Khatanga Saddle

Abstract

—The degree of organic-matter (OM) maturation in Proterozoic, Paleozoic, and Mesozoic deposits in the Anabar–Khatanga saddle has been determined from examination of the reflectance of macerals (mainly vitrinite). The Proterozoic deposits contain only graphite inclusions of uncertain origin. In the Cambrian, Devonian, and Carboniferous strata, OM has transformed predominantly to apocatagenesis grades (AC2–3). Similarly transformed OM (AC1–3) is found in the lower Permian Tustakh and Lower Kozhevnikova formations. In some wells and areas, the degree of OM catagenesis is not higher than МC12–МC2 grades (classification after A.E. Kontorovich). In the Upper Kozhevnikova Formation, catagenesis grades are within МC11–АC1 in the upper Permian and within МC11–МC32 in the Triassic. In the Jurassic deposits, OM has transformed to early mesocatagenesis grades (МC11–МC12) and reached MC2 at the most deeply buried segments. In the Cretaceous strata, OM is less transformed, corresponding to PC3–МC11 or, seldom, higher grades of catagenesis. Some complexes in the Permian, Triassic, and Jurassic–Cretaceous deposits with OM of moderate maturity might be petroleum-promising.