The Labrador Sea formed during rifting between North America and Greenland beginning in the Early Cretaceous, with subsequent seafloor spreading from the Maastrichtian (chron C31) to Early Paleocene (chron C27n) that ended by chron C13 (earliest Oligocene). Early Cretaceous rifting resulted in accumulation of Alexis Formation basalt units and Bjarni Formation nonmarine and marginal marine clastic rocks. In the Late Cretaceous, extension focused further offshore as sag basin conditions formed across the shelf, with a basinwide transgression of Markland Formation shale and localized Freydis Member sandstone development. A Middle Paleocene to Early Eocene regression formed Gudrid Formation shoreline sandstone units, with correlative Cartwright Formation marine shale units. This was followed by an Early Eocene transgression of the Kenamu Formation and Middle Eocene Leif Member shoreline development. During the Late Eocene through Pleistocene, transgression took place once again at the base of the Mokami Formation, with subsequent development of the partly correlative shallow-marine sandstone units of the Saglek Formation.