Source rock geochemistry of Early Silurian black shales of Severnaya Zemlya, Russian Arctic

The Severnaya Zemlya Archipelago is located on the edge of the Arctic Ocean north of the Taimyr Peninsula, separating the Kara and Laptev seas, two potentially vast and apparently different hydrocarbon provinces. The geology of this area is represented by sedimentary, metamorphic and volcanic rocks ranging from the Neoproterozoic to Cenozoic age.

Combined Rock-Eval and other geochemistry analyses on the Silurian samples reveal the presence of early Silurian source rocks on Severnaya Zemlya. The Llandovery Sredny Formation yields organically rich black shale with good source potential and a Type II oil and gas prone bulk source rock quality. The Rock Eval Tmax value suggests that the organic matter is early mature for oil generation. The biomarker characteristics of the Llandovery Sredny shale source rock extract are consistent with a marine algal/bacterial organic matter source and a clay-rich oxic-suboxic palaeoenvironment. The distinctive methyltriaromatic sterane signature obtained, strongly matches Late Ordovician source rock extracts and related oils from the Tarim Basin of China. There is a close similarity in sterane fingerprint and carbon isotope composition between the Sredny shale extract and oils derived from the Silurian Safiq source rock of central Oman.

The occurrence of hydrocarbon in the Silurian of Severnaya Zemlya is clear evidence of an active petroleum system in the region.