The Labrador water is a northwestward expansion regarding the North Atlantic Ocean, through the Charlie-Gibbs break zone when you look at the south to Davis Strait into the north (Figure 2), which separates southern Greenland from Labrador. Rifting and breakup of the margins started through the Early Cretaceous (
85 Ma) according to borehole information (Balkwill 1990). Volcanics of Cretaceous and early Tertiary age onlap the rift structures and synrift sediments. A final period of intense volcanism in the Paleocene in the region of Davis Strait
60 Ma) is from the North Atlantic Magmatic Province (Gill et al., 1999). Unlike the Newfoundland and Nova Scotia margins towards the south, the pre-existing continental crust differs significantly with its many years and crustal properties: through the Paleozoic Appalachian Province when you look at the south, through the Late Proterozoic Grenville Province towards the Early Proterozoic Makkovik Province, last but not least the Archean Nain Province (Figure 9). A review that is recent of properties of those crustal units, predicated on results through the Lithoprobe ECSOOT system, is provided by Hall et al. (2002).
Figure 9. Maps for the Labrador margin showing (a) total sediment depth and (b) free-air gravity. Sedimentary basins and continental terranes are
Following rifting, subsequent seafloor distributing in the Labrador water is documented by magnetic lineations (Roest and Srivastava, 1989), beginning first when you look at the south throughout the Late Cretaceous (
70-80 Ma), then propagating to your north and closing into the eocene that is late
40 Ma) whenever seafloor spreading ceased. An important improvement in distributing taken place at
55 Ma when rifting began splitting Greenland from European countries. During its syn-rift and post-rift period, a tremendous pair of oval-shaped sedimentary basins divided by crustal arches formed along the profoundly subsided crust regarding the Labrador rack (Figure 9). After the initial syn-rift that is coarse-grained, there is a short span of sediment starvation followed closely by a lot of clastic sediment influx through the belated Cretaceous and Tertiary. This resulted in a major seaward progradation of sediment within the rift-age grabens and ridges. Due to the fact cellar proceeded to diminish, successive Tertiary sediment perspectives downlap and seaward that is thicken the rack attained its current place. In contrast, the Southwest Greenland shelf is slim and has now skilled minimal subsidence south of 63°N (Rolle, 1985). Thermal types of borehole information through the Labrador margin had been the first to ever add a larger level of lithospheric versus crustal stretching (Royden and Keen, 1980) to be able to explain its bigger post-rift versus syn-rift subsidence history.
During subsidence associated with the Labrador margin, terrigenous supply stones inside the Upper Cretaceous Bjarni development and Upper Cretaceous to Paleocene Markland development matured mainly to form gasoline. Regarding the 31 wells drilled from the Labrador margin through the 1970’s and very very early 1980’s, there have been six hydrocarbon discoveries of that the biggest ended up being the Bjarni gasoline pool (Bell and Campbell, 1990). Hydrocarbon reservoirs of these discoveries are created in structural traps of Lower and Upper Cretaceous fluvial sandstone overlying cellar horst obstructs.
Figure 10. Level area for seismic profile TLS90-1 throughout the Labrador margin with seismic velocities (in color) from refraction pages. Wells and basement crustal kinds and boundaries as
Clearly, there clearly was significantly less recent coverage that is seismic of Labrador margin compared to the Newfoundland and Nova Scotian margins.
But, because of the restricted width for the Labrador water and seafloor that is relatively simple history, just one local profile had been shot that spans the entire width regarding the basin as well as its conjugate margins (Keen et al., 1994). In addition, a few separate but coordinated refraction pages had been shot along and over the same transect. Mixture of these data has allowed a total level part to be manufactured from seafloor to mantle throughout the whole basin (Chian et al., 1995; Louden et al., 1996). The area over the Labrador margin is shown in Figure 10. Of specific note could be the interpretation of an extensive zone of thinned crust that is continental the external rack and slope, which contrasts with past interpretations of oceanic crust ( e.g. Balkwill et al., 1990). Further seaward, an area of high velocity lower crust, interpreted as partially serpentinized mantle, separates the zones of thinned continental crust (landward) and oceanic crust (seaward). Cellar over the area of serpentinized mantle is relatively flat, in comparison because of the basement that is faulted either part. A prominent sub-basement reflector marks the top the greater velocities of this serpentinized mantle. This sub-horizontal horizon contrasts to your dipping crustal reflectivity to either part. According to this profile and an equivalent one throughout the Southwest Greenland margin, a well-balanced crustal reconstruction for the two conjugate margins during the point of breakup is shown in Figure 11 (Chian et al., 1995). This means that that a highly asymmetric pattern and lack of a lot of mantle melt should have resulted later through the rifting process, contrary to predictions from pure-shear models (Louden and Chian, 1999). It could undoubtedly be interesting to know if this asymmetry is really a feature that is common of margins. A refraction that is subsequent 92-5 (Hall et al., 2002) shows an even more abrupt initial thinning regarding the continental crust further to your north (Figure 9), however it doesn’t sample the whole change in to the oceanic basin.
Figure 11. Feasible scenario for asymmetric crustal breakup of Labrador-Greenland continental block based on balanced crustal cross-sections from velocity models. Crustal sections eliminated during reconstruction (yellow and red) are thought to have created following breakup by serpentinization of mantle (from Chian et al., 1995).