Stratigraphy and geological evolution of the West Greenland margin

The stratigraphy and the geological evolution of the West Greenland continental margin from the Labrador Sea to the Baffin Bay since the Archean are outlined. The summary is based on comprehensive regional studies of seismic stratigraphy combined with other offshore data in comparison to outcrop studies from the Nuussuaq and Thule basins. The timing of the stratigraphic units and key rifting events are well constrained by biostratigraphy and radiometric dating of rock samples. The database involved all deep offshore wells, several shallow wells and nearly all seismic 2D and 3D seismic surveys along the entire West Greenland margin. The geological evolution of the West Greenland continental margin is divided into six overall tectono-stratigraphic phases (I–VI), defined by eight seismic stratigraphic mega-units (A–H): (I) pre-rift and early extension (pre-Cretaceous), (II) early rift (Albian–Cenomanian), (III) subsidence and rifting (Cenomanian–Campanian), (IV) late rift (Campanian–Danian), (V) drift (mainly Paleocene–Eocene), and (VI) post-drift (Oligocene–Present). Proterozoic sedimentary rocks in NE Baffin Bay were recovered in cored boreholes and are correlated to the uppermost part of mega-unit H of which the lower part includes Archean basement bedrocks. In addition, Ordovician carbonates are known from seabed and onshore samples collected farther south. A succession including sandstones, locally conglomerates, and mudstones of Albian–Cenomanian age are widely documented (Kap York, Nuussuaq and Nuuk basins) and correlated to mega-unit G of the early rift phase. Mudstone dominated successions and local sandstones were deposited during subsidence and late rifting phases of mega-units F and E. Transtensional strike-slip related structures, inversion, pull-apart basins, and major volcanic eruptions including subaerial lava flows of the West Greenland Volcanic Province formed during the Paleocene to Eocene drift phase. This occurred when the Greenland plate moved towards northeast and then north as it separated from North America and oceanic crust formed in the Labrador Sea and in central Baffin Bay. Tectonic activity decreased during the late Cenozoic post-drift phase (mega-units A–D), where wide basins evolved, and deltas, mass-flows and contourite drift complexes also formed. Eventually, the glacially affected shelf-edge margins of mega-unit A evolved in W–SW directions with several pulses of ice-sheet advances/retreats and formation of trough-mouth fan systems. The geological evolution of the West Greenland margin is connected to the evolution of the conjugate Canadian margin. The work presented here is a part of the new geological synthesis on the Labrador–Baffin Seaway and the adjacent onshore areas (GSC Bulletin 608).