Labrador Margin 125 Ma) and finished through the belated Cretaceous (


Labrador Margin 125 Ma) and finished through the belated Cretaceous (

The Labrador water is a northwestward expansion associated with North Atlantic Ocean, through the Charlie-Gibbs break area into the south to Davis Strait when you look at the north (Figure 2), which separates southern Greenland from Labrador. Rifting and breakup of these margins started through the Early Cretaceous (

85 Ma) centered on borehole information (Balkwill 1990). Volcanics of Cretaceous and early Tertiary age onlap the rift structures and synrift sediments. Around Davis Strait, one last period of intense volcanism when you look at the Paleocene (

60 Ma) is linked to the North Atlantic Magmatic Province (Gill et al., 1999). Unlike the Newfoundland and Nova Scotia margins towards the south, the pre-existing continental crust varies substantially with its many years and crustal properties: through the Paleozoic Appalachian Province when you look at the south, through the belated Proterozoic Grenville Province to your Early Proterozoic Makkovik Province, last but not least the Archean Nain Province (Figure 9). A present overview of geophysical properties of the 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 continental terranes are

Following rifting, subsequent seafloor distributing in the Labrador water is documented by magnetic lineations (Roest and Srivastava, 1989), beginning first within the south throughout the belated Cretaceous (

70-80 Ma), then propagating towards the north and closing into the eocene that is late

40 Ma) whenever seafloor spreading ceased. A change that is major distributing happened at

55 Ma when rifting began Greenland that is separating from. During its syn-rift and post-rift period, a tremendous group 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 clearly was a short span of sediment starvation followed closely by a great deal of clastic sediment influx through the belated Cretaceous and Tertiary. This generated a major seaward progradation of sediment throughout the rift-age grabens and ridges. Because the cellar proceeded to diminish, successive Tertiary sediment perspectives downlap and thicken seaward as the rack attained its current place. In contrast, the Southwest Greenland rack is slim and contains experienced 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 higher 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 of this Labrador margin, terrigenous supply stones inside the Upper Cretaceous Bjarni development and Upper Cretaceous to Paleocene Markland development matured primarily to form fuel. For the 31 wells drilled regarding the Labrador margin during the 1970’s and very early 1980’s, there have been six hydrocarbon discoveries of that the biggest had been the Bjarni fuel pool (Bell and Campbell, 1990). Hydrocarbon reservoirs for those discoveries are created in structural traps of Lower and Upper Cretaceous sandstone that is fluvial cellar horst blocks.

Figure 10. Depth 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

Demonstrably, there clearly was significantly less recent coverage that is seismic of Labrador margin compared to the Newfoundland and Nova Scotian margins.

But, due to the restricted width associated with Labrador water and easy seafloor distributing history, an individual local profile had been shot that spans the whole width regarding the basin and its particular conjugate margins (Keen et al., 1994). In addition, a few split but coordinated refraction pages were shot along and over the transect that is same. Mix of these data has permitted a depth that is complete to be produced from seafloor to mantle over 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 may be the interpretation of an extensive zone of thinned crust that is continental the exterior rack and slope, which contrasts with past interpretations of oceanic crust ( e.g. Balkwill et al., 1990). Further seaward, an area of high velocity reduced 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 using the faulted cellar to either part. A prominent sub-basement reflector marks the top the bigger velocities associated with the serpentinized mantle. This horizon that is sub-horizontal towards the dipping crustal reflectivity to either side. Centered on this profile and an identical one over the Southwest Greenland margin, a balanced reconstruction that is crustal of two conjugate margins during the point of breakup is shown in Figure 11 (Chian et al., 1995). This suggests that an extremely asymmetric pattern and lack of quite 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 can undoubtedly be interesting to know if this asymmetry is really a common function of those 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 to your north (Figure 9), nonetheless it will not sample the whole change to the oceanic basin.

Figure 11. Viable 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 thought to possess created after breakup by serpentinization of mantle (from Chian et al., 1995).