Labrador Margin 125 Ma) and finished through the belated Cretaceous (
The Labrador water is just a northwestward expansion for the North Atlantic Ocean, through the Charlie-Gibbs break area within the south to Davis Strait within 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 data (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 into the south, through the belated Proterozoic Grenville Province into the Early Proterozoic Makkovik Province, and lastly the Archean Nain Province (Figure 9). A current summary of geophysical properties among these crustal units, centered on outcomes from 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 terranes that are continental
Following rifting, subsequent seafloor distributing within the Labrador water is documented by magnetic lineations (Roest and Srivastava, 1989), beginning first into the south throughout the belated Cretaceous (
70-80 Ma), then propagating towards the north and closing in the eocene that is late
40 Ma) when seafloor spreading ceased. A significant improvement in distributing happened at
55 Ma when rifting began Greenland that is separating from. During its syn-rift and post-rift period, an immense collection of oval-shaped sedimentary basins divided by crustal arches formed along the profoundly subsided crust for the Labrador shelf (Figure 9). Following a initial coarse-grained syn-rift deposits, there clearly was a little while of sediment starvation followed closely by a massive amount 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 position. In contrast, the Southwest Greenland rack is slim and contains skilled little if any subsidence south of 63°N (Rolle, 1985). Thermal types of borehole information through the Labrador margin had been the first to ever consist of a greater level of lithospheric versus crustal stretching (Royden and Keen, 1980) so that you can explain its bigger post-rift versus syn-rift subsidence history.
During subsidence associated with the Labrador margin, terrigenous supply stones in the Upper Cretaceous Bjarni Formation and Upper Cretaceous to Paleocene Markland development matured mainly to create gasoline. For the 31 wells drilled regarding the Labrador margin through the 1970’s and very early 1980’s, there have been six hydrocarbon discoveries of that your largest 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 sandstone that is fluvial cellar horst obstructs.
Figure 10. Level section for seismic profile TLS90-1 over the Labrador margin with seismic velocities (in color) from refraction pages. Wells and basement crustal kinds and boundaries as
Clearly, there is certainly notably less recent coverage that is seismic of Labrador margin compared to the Newfoundland and Nova Scotian margins.
Nonetheless, due to the restricted width for the Labrador water and easy seafloor distributing history, an individual local profile had been shot that spans the entire width associated with basin and its particular conjugate margins (Keen et al., 1994). In addition, a few separate but coordinated refraction pages had been shot along and over the exact same transect. Mixture of these information has permitted an entire level area to be manufactured from seafloor to mantle over the whole basin (Chian et al., 1995; Louden et al., 1996). The part over the Labrador margin is shown in Figure 10. Of particular note could be the interpretation of a broad 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, a area of high velocity reduced crust, interpreted as partially serpentinized mantle, separates the zones of thinned crust that is continentallandward) and oceanic crust (seaward). Cellar over the area of serpentinized mantle is relatively flat, in comparison utilizing the faulted basement to either part. A prominent sub-basement reflector marks the top the greater velocities associated with serpentinized mantle. This horizon that is sub-horizontal towards the dipping crustal reflectivity to either part. Predicated on this profile and an identical one over the Southwest Greenland margin, a balanced crustal reconstruction associated with two conjugate margins in the point of breakup is shown in Figure 11 (Chian et al., 1995). This suggests that a extremely asymmetric pattern and lack of a lot of mantle melt will need to have resulted later through the rifting process, as opposed to predictions from pure-shear models (Louden and Chian, 1999). It could definitely be interesting to know if this asymmetry is really a typical function of the margins. A refraction that is subsequent 92-5 (Hall et al., 2002) shows a far more abrupt initial thinning associated with the continental crust further into the north (Figure 9), nonetheless it will not sample the whole change to the oceanic basin.
Figure 11. Available situation 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 assumed to own created breakup that is following serpentinization of mantle (from Chian et al., 1995).