Organic geochemistry of the Lower Jurassic Sortehat Formation, Jameson Land, East Greenland

Abstract

Biomarker analyses of Lower Jurassic shales from the Sortehat Formation, Jameson Land, central East Greenland carried out in combination with palynological studies demonstrate deposition in a fresh to brackish water environment, which became increasingly saline towards the top. The formation is regionally immature to early mature with respect to hydrocarbon generation, and the lowermost 2–20 m have a fair generation potential. Biomarker analysis of the brackish water part shows dominance of C₁₆–C₂₁ n-alkanes, high pristane/phytane ratios, high hopane/sterane ratios, high relative amounts of C₂₉–C₃₁ hopanes and C₂₇17α-trisnorhopane. Steranes are dominated by C₂₉ isomers. The organic matter is composed of bacteria, algae and land plants interpreted from biomarker distributions. The combined data set suggests that deposition took place during an overall rise in relative sea level.