Sedimentology and geochemistry of Late Jurassic organic-rich shelfal mudstones from East Greenland: regional and stratigraphic variations in source-rock quality

Abstract

Late Jurassic (Late Oxfordian–Early Volgian) sediments exposed across a wide area of East Greenland are dominated by organic-rich mudstones and sandy mudstones and reach a maximum thickness of 500 m. The facies are characterized by parallel-laminated, generally unbioturbated mudstones, in some cases containing thin sandstone laminae. Deposition occurred in an offshore shelf environment, with water depths difficult to constrain. In the northern sections, heterolithic, sandier units occur at the base of the mudstone succession, marking a gradual transition from the underlying shallow-marine sandstones. Mudstones in the south (Milne Land–Jameson Land) are more oil prone, with greater dilution by terrestrially derived Type III/IV kerogen in the north (Wollaston Forland–Kuhn Ø). In both areas there is an improvement in source-rock quality and oil proneness from proximal to distal settings, with the geochemical data in agreement with the palaeogeographical interpretation. In the south, the Late Kimmeridgian to Early Volgian marks the maximum westward transgression of source-rock facies and also represents the richest source interval. In the north there is a decrease in sand content through the Late Oxfordian–Kimmeridgian, although trends in source-rock quality are less clear. Whilst the northern sections are predominantly gas prone, some marginally oil-prone mudstones do occur. The Vøring and Møre basins were situated immediately to the east of Greenland in the Late Jurassic. The presence of a continuous blanket of potential source rocks in East Greenland and the eastward improvement in source-rock properties implies that good quality oil-prone source rocks of Late Jurassic age are likely to be present in the Vøring and Møre basins