New insight into the structure of the Nuussuaq Basin, central West Greenland

Interpretation of seismic and magnetic data, forward modelling of gravity p rofiles and a reappraisal of all available data on faults onshore provides the first revision in 30 years of our understanding of the structure of the Nuussuaq Basin, central West Greenland. In the western part of the area Me sozoic sediments at least 6 km and possibly up to 10 km thick occur in an e arly rift basin dominated by N-S faults. Recently discovered oil in surface seeps and in shallow boreholes occurs almost exclusively in the early rift basin. In the east, sediments are thinner, and faults trend both N-S and W NW-SSE, the latter parallel to shear zones in the adjoining basement area. The eastern area may be part of a Late Cretaceous thermal subsidence basin. Renewed faulting involving both reactivation of older faults and generatio n of new faults took place in latest Cretaceous-early Paleocene time, and w as followed by extensive erosion and phases of incision and infilling of va lley systems. Renewed subsidence occurred immediately prior to the eruption of extensive middle Paleocene and Eocene continental flood basalts. The fi nal phase of faulting took place in connection with sea-floor spreading in Baffin Bay and the Labrador Sea during the Eocene. Movement of North Americ a relative to Greenland was transferred from the Labrador Sea to Baffin Bay along a strike-slip fault system in continental crust, the Ungava transfor m fracture zone. A splay of this system gave rise to a prominent SW-NE faul t in the western part of the basin. (C) 1999 Elsevier Science Ltd. All righ ts reserved.