Northern Labrador Research Articles

Salinity tolerance of freshwater acclimated, small‐sized Arctic charr, Salvelinus alpinus from northern Labrador

Arctic charr, Salvelinus alpinus, less than 150 mm in size were frequently captured at sea in northern Labrador in areas where salinities of 30‰ or higher had been recorded. These captures were inconsistent with many earlier reports for other areas that indicated Arctic charr less than 150 mm in size were not found at sea. A series of salinity challenge tests was carried out in the field, using wild Ikarut River charr, and in the laboratory, using cultured Fraser River charr, to understand more about the potential fate of these small fish. The results of challenge tests with small Arctic charr (< 120 mm) indicated that at intermediate salinities (10–20‰), these fish can readily survive. In laboratory tests with salinities at 30‰, survival was size dependent and would suggest that in natural situations, small charr would require periodic access to fresh or brackish water to stay alive. The influence of water temperature on salinity tolerance may be important when fish are exposed to temperatures that are below 0° C.

Salinity tolerance of freshwater acclimated, small-sized Arctic charr, Salvelinus alpinus from northern Labrador

Salinity tolerance of freshwater acclimated, small-sized Arctic charr, Salvelinus alpinus from northern Labrador

Structure of Archean crust and passive margin of southwest Greenland from seismic wide‐angle data

To investigate the structure and composition of the Archean crust beneath the shelf of southwest Greenland parallel to the passive margin, we conducted an onshore/offshore seismic wide‐angle experiment in 1989. One of our goals was to obtain a velocity/depth profile along the thinned continental or transitional crust to place constraints on the magmatic rifting history in the northern Labrador Sea. Seismic recording instruments at four locations along the coast recorded energy from an air gun array up to 400 km distance. Due to the dense shot spacing of 100 to 150 m we were able to identify continuous reflected and refracted phases from the upper to lower crust. Results from a one‐dimensional extremal inversion indicated a high‐velocity zone (HVZ) with P wave velocities of more than 7.2 km/s at the bottom of the transitional crust. Combined two‐dimensional travel time forward modeling and inversion produced a velocity/depth model that contains midcrustal and lower crustal discontinuities between 12 and 25 km depth and a Moho dipping northward at 30 to 42 km depth. An average crustal velocity of about 6.6 km/s indicates a high portion of mafic components in the crust. The lowermost crust consists of a HVZ with a maximum thickness of 8 km and temperature‐corrected velocities of 7.5 to 7.85 km/s. The HVZ may be explained by an underplated igneous complex often observed under passive margins worldwide. Metamorphism to garnet‐pyroxene‐granulite during postrift isobaric cooling of the 30‐ to 40‐km‐deep, thinned continental crust could explain the velocities that are higher than on other margins. A large volume of magmatic material must have been added to the crust but did not produce extrusions. Magmatic underplating of the thinned continental or transitional crust of SW Greenland is likely associated with a possible hot spot magmatism in the Davis Strait and Baffin Bay region. Magmatism associated with continental rifting was found to reach farther south along the northern and central part of the Archean block than previously thought.

Observations of an interaction between a barren-ground Black Bear, Ursus americanus, and a Wolf, Canis lupus, at a Wolf den in northern Labrador

Observations of an interaction between a barren-ground Black Bear, Ursus americanus, and a Wolf, Canis lupus, at a Wolf den in northern Labrador

Psychiatry in Northern Newfoundland and Labrador

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Fluorite-bearing early and middle proterozoic granites, Okak Bay area, labrador: Geochronology, geochemistry and petrogenesis

Three discrete age groups of relatively fractionated, fluorite-bearing, post-tectonic Proterozoic granitoid rocks have been identified in the Okak Bay area of Labrador on the basis of U-Pb zircon geochronology. Two of the groups occur entirely within the Archean Nain Province; the third occurs largely within the Early Proterozoic Churchill Province (Torngat Orogen). None of the three episodes of granitoid magmatism can be directly linked to orogenic activity in its immediate surroundings. Although all three granite groups are broadly similar, petrologically and chemically, to the felsic rocks of the anorogenic Elsonian (≈1450−1290 Ma) Nain Plutonic Suite (NPS), only one of the dated units can be correlated confidently with Elsonian magmatism. The other two groups represent significantly older anorogenic or postorogenic magmatism. The oldest unit, the Wheeler Mountain granites of the Nain Province has yielded a U-Pb age of about 2135 (2134± 3 1, 2137±2) Ma. A major tectonothermal event of this age has not been previously identified in northern Labrador, and the origin of the granites is uncertain. Three small intrusions on offshore islands (White Bear, Saddle, Opingiviksuak) in the Nain Province were intruded about 1775 (1774± 2 1,1776± 4 2, 1774± 2 1) Ma. These granites may have been intruded post-kinematically into a stable Archean foreland representing a delayed effect of a preceding collisional event (Torngat Orogeny) between Nain and Churchill Province to the west. The youngest unit dated, at about 1318 (1319±2, 1316± 2 3) Ma, is Umiakovik Lake batholith which crops out largely within the eastern Churchill Province, and is one of the largest granitoid intrusions of the NPS. The age confirms that it formed an integral part of the Elsonian magmatic event, but both Umiakovik Lake batholith and nearby 1320 Ma Makhavinekh Lake pluton are significantly older than some basic members of the NPS in the coastal area to the southeast. Nd and Sr isotopic data demonsrate that Archean protoliths formed significant components of the source materials for all three of these Proterozoic granitoid magmas. This source was supplemented by one or more Proterozoic episodes of lower crustal intrusion and underplating by juvenile mantle-derived magmas that occurred in the region.

Sea‐ice properties off Labrador and Newfoundland during LIMEX ‘89

Abstract During the cold winter of 1988/89, ice coverage was abnormally high over the Newfoundland Shelf, but was low over the northern Labrador Shelf. The pack‐ice aligned in bands parallel to the coast and bathymetry, with thin ice and open water occurring inshore of the thick pack‐ice, a result of ice divergence along the coast and the large ice‐melt rates at the shelf break. Freezing degree‐day models predicted higher than normal ice thicknesses at land‐fast ice stations when climatic mean snow‐layer depths were used. However, observed ice thicknesses were below normal, which could only be predicted when observed snow conditions were used. Offshore winds generated ice divergence, which stimulated increased ice growth in the nearshore region, which in turn caused the large surface mixed layer depths and high salinity values. Ice drift rates obtained from satellite‐tracked ice beacons had two‐week averaged speeds of 18 km d−1 equal to the large horizontal melt rates of the ice edge over the shelf break bordering the Labrador Sea. Ice drift rates of up to 75 km d−1 were observed during strong northwesterly winds over the continental slope where the Labrador Current is located.

Encalypta affinis subsp. macounii and E. brevipes New to Eastern North America from the Torngat, Northern Labrador, Canada

Encalypta affinis subsp. macounii (Aust.) Hort. and E. brevipes Schljak. are newly recorded for eastern North America on specimens from the Torngat Mountains, northern Labrador. Both taxa appear to be glacial relicts, and their Torngat populations are considerably disjunct from other known localities in Greenland and western North America. They thus provide additional evidencefor the existence of biological refugia in the Torngat through at least part of the Pleistocene glacial period. In her recent monograph of the genus, Horton (1983) attributed 15 species and two additional subspecies of Encalypta to North America. Only seven of these 17 taxa (E. affinis Hedw. subsp. affinis, E. alpina Sm., E. brevicolla (B.S.G.) Bruch ex Aongstr., E. ciliata Hedw., E. longicolla Bruch, E. procera Bruch, E. rhaptocarpa Schwaegr.) are recognized from eastern North America, excluding Greenland (Crum & Anderson 1981; Horton 1983; Ireland et al. 1987). On the basis of collections from the Torngat Mountains, northernmost Labrador, E. affinis subsp. macounii and E. brevipes may be added to the eastern North American moss flora. All specimens cited are deposited at NFLD. Encalypta affinis subsp. macounii (Aust.) Horton.-According to Horton (1983), this taxon is known elsewhere in North America from the Western Cordillera, ranging from Alaska-Yukon south to northern Washington and Montana. Otherwise it is restricted to a very few localities in Fennoscandia and a single site in the Swiss Alps. The Torngat populations are disjunct by ca. 3,200 km from the nearest known localities in western North Amer-

The intergeneric hybrid origin ofPoa labradorica (Poaceae)

Phytogeographic, ecological, morphological, anatomical, cytological, isozyme, and endonuclease restriction site evidence is presented demonstrating thatPoa labradorica is of intergeneric hybrid origin betweenDupontia fisheri subsp.psilosantha (pistillate parent) andPoa eminens (staminate parent).Poa labradorica is endemic to recently deglaciated areas of northern Quebec and Labrador which are within the overlapping range of the putative parents. Incapable of sexual reproduction,P. labradorica dominates large areas of coastal marsh through vigorous production of rhizomes. Most morphological, anatomical, cytological, isozyme, and DNA characters studied inP. labradorica showed states intermediate or additive to those of the putative parents.

The Archaean gneiss complex of northern Labrador A review of current results, ideas and problems

1. The early Archaean rocks in northern Labrador can be subdivided into the ea. 3.78 Ga Nulliak supracrus­tal association, the migmatitic Uivak I gneisses, the dominant phase of which was emplaced at ea. 3.73 Ga, and the Uivak II augen gneiss. Inherited low-U rounded inclusions within igneous zircons in the Uivak I gneisses have ages between 3.73 and 3.86 Ga and are more likely to have been derived from a pre-existing high-grade metamorphic gneiss complex than from the Nulliak association. In the early Archaean there were probably several rapid cycles of sedimentary deposition and volcanism followed by emplacement of major plutons. Mid Archaean gneisses are more abundant in northern Labrador than previously realised. The late Archaean metamorphic history of these gneisses is different from the history of the early Archaean gneisses. Whereas an important part of the mid Archaean suite was emplaced in granulite facies and retrogressed at the time of granitoid veining at ea. 2.99 Ga, the major part of the early Archaean rocks were reworked under granulite facies conditions in a sequence of closely spaced events between 2. 7 and 2.8 Ga. The two groups of gneisses had different metamorphic histories until ea. 2.7 Ga, but late and post-tectonic granites of 2.5- 2. 7 Ga age cut across both. It is suggested that the terrane model in southern West Greenland can be extended to Labrador and that tectonic intercalation of early and mid Archaean gneisses took place around 2.7 Ga. Correlation between the Maggo gneisses around Hopedale, mid Archaean gneisses in northernmost Labrador and gneisses from the Akia terrane in West Greenland is suggested. Like the Malene supracrustals in West Greenland the Upernavik supracrustals in Labrador are composite associations, the youngest of which are thought to have been deposited around 2. 7 Ga.

Lithotectonic elements and tectonic evolution of Torngat Orogen, Saglek Fiord, northern Labrador

A cross section of the eastern part of the Early Proterozoic Torngat Orogen is exposed along Saglek Fiord in northern Labrador. It shows the transition from a foreland, through a frontal zone to the internal zone of the orogen, the latter being composed of two lithologically distinct terranes that are part of Abloviak shear zone, a crustal-scale transcurrent shear zone with a sinistral sense of displacement. One of these terranes is parautochthonous with respect to the foreland, the other is allochthonous and interpreted as being separated from the parautochthon by a cryptic suture.Ramah Group, an Early Proterozoic supracrustal sequence that lies unconformably on Archean gneisses in the foreland, can be traced across the frontal zone, but does not occur in Abloviak shear zone in the Saglek area.Tectonic evolution of Torngat Orogen involved crustal thickening to approximately double normal thickness, with transcurrent shearing of the thickened crust taking place during peak metamorphic conditions. Synmetamorphic uplift occurred synchronously with transcurrent shearing, and was followed by imbrication of orogenic zones along late thrust–reverse faults. Available age determinations suggest that peak metamorphism predated uplift by about 50 Ma. 39Ar/40Ar dating of hornblende from Abloviak shear zone has yielded ages of 1790–1750 Ma, some 15–65 Ma younger than recent estimates of the age of late faults, thus indicating slow and irregular uplift throughout the orogen.The orogenic history of Torngat Orogen is compatible with evolution in an oblique collision zone between two Archean cratonic blocks, and their subsequent welding into a single continental fragment that itself became incorporated into proto-Laurentia.

New evidence on the structure of the Labrador Sea/Greenland continental margin

A 275 km section of a regional seismic reflection profile from the Greenland side of the Labrador Sea has been reprocessed and interpreted. Three zones of different structural style have been identified, the innermost of which is block-faulted. Magnetic modelling based on the seismic line shows that sea-floor spreading anomalies are confined to the outermost zone and the oldest identified anomaly is 27N. All attempts to model the area landward of anomaly 27N as a series of remanent magnetizations of alternating polarity failed. However a model in which the innermost zone is interpreted as extended and block-faulted continental crust and the intermediate zone as continental crust intruded and overlain by reversely magnetized igneous material fits the magnetic and seismic data. It is concluded that, at least in the northern Labrador Sea, sea-floor spreading started in Palaeocene times (chron 27), and large areas formerly thought to be underlain by oceanic crust should now be considered to be continental. One plate kinematic consequence may be a reduced need to postulate large strike-slip movements along Nares Strait.

Adolescent and Pre-Adolescent Suicide in Newfoundland and Labrador

This study investigated suicides by people aged ten to 19 in Newfoundland and Labrador from 1977 to 1988. It is the first study of suicide in the province to use the records of death from all eight hospital pathology departments in the province and from the office of the Chief Forensic Pathologist. Cases were selected for the study using standardized criteria, independent of the manner of death recorded on the death certificate. A suicide rate of 4.37 per 100,000 was found. This rate and the age- and sex-specific suicide rates are lower than the official figures for Canada but higher than those reported in earlier Newfoundland studies. The rate for males was nearly five times the female rate, and the rate for people aged 15 to 19 was nearly six times that of people aged ten to 14. Suicide rates for Labrador were higher than for the island portion of the province for both Native and for non Native adolescents. Extremely high rates of suicide were found only among the Native population living in Northern Labrador, while none were recorded for Native people elsewhere. Firearms accounted for 54% and hanging for 33% of all suicides. Thirty percent of suicides occurred on a Saturday. Only 36 of the 63 deaths included in this study were designated as suicide on death certificates. The higher rate of under-reporting of suicide than in other jurisdictions suggests that official rates may not be useful for comparisons. The reasons for the high rate of under-reporting are discussed.

Predicting Fish Mercury Levels from Physical Characteristics of Boreal Reservoirs

Reservoir formation has often resulted in increased fish mercury levels. Predicting the potential for increase prior to impoundment would be useful in future environmental impact assessment.. We developed several linear models relating mercury burdens of northern pike (Esox lucius), walleye (Stizostedion vitreum), and lake whitefish (Coregonus clupeaformis) to physical characteristics of 21 lakes and reservoirs in the Churchill River diversion region of northern Manitoba. Ratios of flooded terrestrial area to water volume of the reservoir itself (within-lake effects) and of inflowing waters (upstream effects) were able to explain 76–84% of the variation in mean mercury burden. Upstream effects consistently accounted for more variation than within-lake effects. We tested these models using data from 18 Canadian lakes and reservoirs. Manitoba reservoirs generally fit the models well. The largest deviations of observed mercury levels from predicted mercury levels were for reservoirs of northern Quebec and Labrador We attribute this to differences in the relative contributions of within-lake effects and upstream effects between reservoirs of this region and those used to build the models. Future models should refine the relative contributions of these two components for individual reservoirs.

Natural Hybridization between Arctic Char (Salvelinus alpinus) and Brook Trout (S. fontinalis): Evidence from Northern Labrador

Electrophoretic analysis of successive samples of Salvelinus collected in the Fraser River watershed of northern Labrador in 1984 and 1986 revealed the existence of natural hybrids between Arctic char (Salvelinus alpinus) and brook trout (S. fontinalis). We examined 11 electrophoretic loci in liver tissue; 10 loci were informative and six were diagnostic of the two species and their hybrids. The electrophoretic phenotypes of some hybrid specimens sugested that they were second-generation hybrids and/or backcrosses to the parental species. Hybrids were represented by six different year classes, indicating that crossing between the species in the system is a regular occurrence. The hybrids, although visually difficult to distinguish from brook trout, were meristicaîly intermediate or more closely resembled Arctic char. The observations raise a number of questions regarding the ecological circumstances promoting hybridization in the evolution of Arctic char and brook trout populations. The results stress the need for restrictions on introducing brook trout into systems with original populations of Arctic char. Further, Arctic char from the Fraser River are commonly used for aquaculture research and development; therefore, there is a clear need to screen fish carefully to determine whether or not they represent introgressed gene pools.

Late quaternary organic carbon cycles and paleoproductivity in the Labrador Sea

Accumulation rates of (marine) organic carbon and estimates of paleoproductivity from organic carbon data indicate distinct late Quaternary glacial/interglacial cycles at Ocean Drilling Program (ODP) Site 646. During the last 240,000 years, surface-water productivity was significantly higher in the northern Labrador Sea during interglacial than during glacial times (70 to 170 gC/m2/yr vs. 30 to 70 gC/m2/yr). The reduced glacial productivity is probably caused by a closed sea-ice cover dominating the northern Labrador Sea during glacial intervals.

A Newfoundland floating factory whaling expedition

AbstractModern shore station whaling spread from Norway to Newfoundland in 1896 with development of the Cabot Steam Whaling Co Ltd. Their success stimulated formation of a second company, the Newfoundland Steam Whaling Co Ltd, which in 1908 mounted a pelagic expedition to hunt in both hemispheres, particularly from the South Orkney and South Shetland Islands and off northern Labrador. The expedition was a failure, and Newfoundland whaling remained a totally shore-based industry until cessation in 1972.

Decompression Reactions and P--T Conditions in High-grade Rocks, Northern Labrador: P--T--t Paths from Individual Samples and Implications for Early Proterozoic Tectonic Evolution

Decompression Reactions and P--T Conditions in High-grade Rocks, Northern Labrador: P--T--t Paths from Individual Samples and Implications for Early Proterozoic Tectonic Evolution

Evidence for extreme mantle fractionation in early Archaean ultramafic rocks from northern Labrador

Samarium–neodymium isotope data for tectonically interleaved fragments of lithospheric mantle and meta-komatiite from the North Atlantic craton provide the first direct record of mantle differentiation before 3r800 Myr ago. The results confirm the magnitude of light-rare-earth-element depletion in the early mantle, and also its depleted neodymium isotope composition. The mantle fragments were able to retain these ancient geochemical signatures by virtue of having been technically incorporated in buoyant felsic crust, thus escaping recycling and homogenization by mantle convection.

Project SYD VEST SEIS - 3285 km of multichannel seismic data acquired on the southern West Greenland shelf

During the three years since 1988, there has been renewed activity within the Geological Survey of Greenland (GGU) to reassess the geology and petroleum prospectivity of the southern West Greenland offshore area (Chalmers, 1989; Chalmers, 1990; Chalmers & Pulvertaft, in press; Ottesen, 1991). Pulvertaft (1991) gives a summary of the present state of the re-evaluation. This work has shown that the geology of the northern Labrador Sea and offshore southern West Greenland is poorly understood. A number of questions about the area's petroleum prospectivity remain unanswered despite re-interpretation and in some cases reprocessing of the existing seismic data. These problems derive from limitations in both the quality and extent of the existing seismic coverage.