Labrador Sea and Baffin Bay from a Deep Seismic Perspective

Thomas Funck

Separation of Greenland from the North American plate resulted in the formation of two oceanic basins comprising the Labrador Sea and Baffin Bay. These two basins are linked by a bathymetric high in the Davis Strait region. Three different continental margin styles are encountered in this region. Non-volcanic margins with serpentinized mantle in the continental-ocean transition zone characterize the margins in the southern Labrador Sea as well as the northern Baffin Bay. In contrast, seaward-dipping reflection sequences and high-velocity lower crust are found along the volcanic margins of southern Baffin Bay and northern Labrador Sea. The transform margin in Davis Strait is influenced by widespread magmatic activity that resulted in the formation of thick series of lava flows, intrusions and addition of mafic material to the lower crust as imaged by high-velocity lower crustal layers. Increased interest in the region over the last ten years has resulted in the acquisition of a substantial amount of seismic data by both academia and industry. These new data have increased our understanding of the complex tectonic development of the Labrador Sea and Baffin Bay. Two recent seismic experiments are of particular interest. The DAVIS GATE project in 2008 collected coincident reflection and refraction seismic data along three lines in Baffin Bay and Davis Strait. This experiment brought the first unequivocal evidence for oceanic crust in southern Baffin Bay where no clear magnetic spreading anomalies are found. The Greenland continental margin in southern Baffin Bay is also heavily influenced by volcanism. Seaward dipping reflectors and basalts are extending up to at least 74° N. A north-south striking zone with high P-wave velocities can be correlated through the entire Davis Strait, indicating either mafic intrusions or the formation of new igneous crust along the Ungava transform system. The SIGNAL 2009 experiment collected refraction seismic data in southern Labrador Sea along pre-existing reflection seismic lines. One focus area was the Eirik Ridge off South Greenland where the data image the non-volcanic SW Greenland continental margin that was overprinted by magma associated with the later break-up of the volcanic Southeast Greenland margin. Volcanic sequences up to 4 km thick are identified on the ridge, while an up to 8-km-thick high-velocity lower crust is observed beneath the ridge. The reflection seismic data indicate the presence of inner and outer seaward dipping reflection sequences separated by an outer basement high. This suggests a subaerial formation of the lavas on the ridge. Cooling and loss of dynamic support by the Iceland plume resulted in the subsidence of the ridge. Data in the vicinity of the extinct Labrador Sea spreading axis indicate a thin oceanic crust (3.5 to 5 km thick) and a possible oceanic core complex and exhumation of mantle.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013