REGIONAL STRATIGRAPHIC UNDERSTANDING OF THE LABRADOR­–BAFFIN SEAWAY

The Labrador–Baffin Seaway—which includes the Labrador Sea, Davis Strait, and Baffin Bay—began forming during Early Cretaceous rifting between the paleo-North American and Greenland plates. Regional geophysical and stratigraphic studies of the resultant offshore and associated onshore basins have been undertaken for decades, but our understanding of the tectonostratigraphic evolution and relationship of the margins of the seaway is somewhat uncertain. To resolve this, we correlated the lithology, ages, paleoenvironments, and unconformities, as well as integrated seismic stratigraphic frameworks, for the conjugate margins and divided the stratigraphy into Cretaceous, lower Cenozoic, and upper Cenozoic intervals, with relationships illustrated in conjugate margin seismic profiles and distribution maps. During the Early Cretaceous, localized basins formed and were infilled with nonmarine and shallow marine strata, succeeded by a transgressive, Upper Cretaceous marine mudstone with minor sandstones as rifting continued and widespread subsidence ensued. Seafloor spreading began in the central Labrador Sea in the Maastrichtian, but propagated regionally by the Early Paleocene, coincident with significant volcanism centered in the Davis Strait. At about the same time, regional regression occurred, and a localized middle Paleocene unconformity developed along the western margin of the seaway, but a significant unconformity developed to the east. The overlying lower Cenozoic interval (Middle Paleocene to Middle Miocene) includes a period of basin inversion that started in the Late Paleocene due to strike-slip motion related to a regional change in seafloor spreading direction. Initial shallow marine and nonmarine strata are succeeded by a Lower Eocene transgressive phase. Spreading ceased in the Late Eocene, and the top of the lower Cenozoic interval is marked by missing section at the base of major clinothems developed within the overlying upper Cenozoic interval. Progradation during this latest interval locally built-out the shelf, with sediments further blanketing the deep water. Our regional correlations help to construct a more complete understanding of the tectonostratigraphic evolution of the Labrador–Baffin Seaway, as well as highlight margin-specific and localized events.