Tectono-sedimentary evolution of the Paleogene succession offshore Northeast Greenland

Abstract

The large-scale geological evolution of the Northeast Greenland shelf is interpreted on the basis of Cenozoic seismic mega-sequences, which are dated by comparison to the knowledge from onshore East Greenland. However, no detailed studies exist of the tectonostratigraphic development during the Paleogene period, when the break-up between Greenland and Eurassia occurred. In this study, we examine the details of the geological development by analysis of the available seismic data in a rift to drift margin context, and we give a detailed seismic stratigraphic interpretation of the deposited units. A threefold subdivision of the presumed Paleogene shelf succession is suggested based on correlation between strata geometries and the break-up history of the Northeast Greenland margin. Deposition took place in two basins, the Danmarkshavn Basin in the west and the Thetis Basin in the east, separated by the Danmarkshavn Ridge. The first recorded Paleogene sediments in the Danmarkshavn Basin are wedge/fan complex, Unit 1, which is referred to a pre-drift or pre-volcanic setting. The overlying, prograding Units 2–4 are interpreted to be deposited during the break-up phase and are inferred to form the syn-drift or syn-volcanic interval. The aggrading Units 5–6 display passive, thermal subsidence in a post-volcanic setting following continental break-up. Detailed seismic interpretation indicates that the pre-volcanic succession is dominated by a complex of highstand prograding wedges and lowstand basin floor fans. The syn-drift succession is interpreted to be shallow marine and relatively coarse grained due to dominance of prograding units with steep angles of the foresets constrained to the Danmarkshavn Basin. Finally, the post-volcanic succession is interpreted to primarily consist of fine-grained sediments deposited below wave base, in a deep, shelf-wide basin. The pre-volcanic units (Units 1–3) are only recognized in the Danmarkshavn Basin, and not until the syn-volcanic phase was the Danmarkshavn Ridgeoverstepped and sedimentation became coherent across the entire shelf. This pattern continued during the post-volcanic thermal cooling phase.