The Labrador water is a northwestward expansion for the North Atlantic Ocean, through the Charlie-Gibbs break area into the south to Davis Strait into the north (Figure 2), which separates southern Greenland from Labrador. Rifting and breakup of those margins started through the Early Cretaceous (
85 Ma) predicated on borehole information (Balkwill 1990). Volcanics of Cretaceous and early Tertiary age onlap the rift structures and synrift sediments. In the near order of Davis Strait, your final amount of intense volcanism within the Paleocene (
60 Ma) is associated with 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 belated Proterozoic Grenville Province into the Early Proterozoic Makkovik Province, last but not least the Archean Nain Province (Figure 9). A review that is recent of properties among these crustal devices, centered on outcomes through the Lithoprobe ECSOOT system, is written 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 terranes that are continental
Following rifting, subsequent seafloor distributing within the Labrador water is documented by magnetic lineations (Roest and Srivastava, 1989), beginning first when you look at the south throughout the belated Cretaceous (
70-80 Ma), then propagating into the north and closing in the eocene that is late
40 Ma) whenever seafloor spreading ceased. A change that is major distributing taken place at
55 Ma when rifting began breaking up 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 for the Labrador rack (Figure 9). After the initial syn-rift that is coarse-grained, there was clearly a brief period of sediment starvation followed closely by a great deal of clastic sediment influx through the belated Cretaceous and Tertiary. This resulted in a seaward that is major of sediment within the rift-age grabens and ridges. While the 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 little if any subsidence south of 63°N (Rolle, 1985). Thermal types of borehole information through the Labrador margin were the first ever to add a better level of lithospheric versus crustal stretching (Royden and Keen, 1980) so that you can explain its larger post-rift versus syn-rift subsidence history.
During subsidence for the Labrador margin, terrigenous supply rocks inside the Upper Cretaceous Bjarni development and Upper Cretaceous to Paleocene Markland development matured mainly to make gas. Regarding the 31 wells drilled from the Labrador margin through the 1970’s and very early 1980’s, there have been six hydrocarbon discoveries of that the biggest was the Bjarni fuel pool (Bell and Campbell, 1990). Hydrocarbon reservoirs for these discoveries are created in structural traps of Lower and Upper Cretaceous sandstone that is fluvial basement horst obstructs.
Figure 10. Level area for seismic profile TLS90-1 over the Labrador margin with seismic velocities (in colour) from refraction pages. Wells and basement crustal kinds and boundaries as
Demonstrably, there clearly was a lot less recent seismic coverage of this Labrador margin compared to the Newfoundland and Nova Scotian margins.
Nevertheless, due to the restricted width associated with the Labrador Sea and simple and easy seafloor distributing history, an individual local profile had been shot that spans the whole width associated with the basin and its own conjugate margins (Keen et al., 1994). In addition, a few split but coordinated refraction pages had been shot along and over the transect that is same. Mixture of these information 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 part throughout the Labrador margin is shown in Figure 10. Of particular note may be the interpretation of an extensive zone of thinned continental crust beneath 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 reasonably flat, on the other hand because of the basement that is faulted either part. A prominent sub-basement reflector marks the top the bigger velocities associated with the serpentinized mantle. This horizon that is sub-horizontal to your dipping crustal reflectivity to either part. Predicated on this profile and seniorpeoplemeet an identical one throughout the Southwest Greenland margin, a well-balanced crustal reconstruction regarding the two conjugate margins during the point of breakup is shown in Figure 11 (Chian et al., 1995). This suggests that a very asymmetric pattern and lack of quite a lot of mantle melt should have resulted later through the rifting process, as opposed to predictions from pure-shear models (Louden and Chian, 1999). It can undoubtedly be interesting to know if this asymmetry is a typical function of those margins. A refraction that is subsequent 92-5 (Hall et al., 2002) suggests a far more abrupt initial thinning regarding the continental crust further into the north (Figure 9), however it will not sample the entire change in to the oceanic basin.
Figure 11. Feasible situation for asymmetric crustal breakup of Labrador-Greenland block that is continental on balanced crustal cross-sections from velocity models. Crustal sections eliminated during reconstruction (yellow and red) are thought to own created after breakup by serpentinization of mantle (from Chian et al., 1995).