Eastern Newfoundland Research Articles

Population Dynamics of Greenland Halibut in the Gulf of St. Lawrence

Greenland halibut, Reinhardtius hippoglossoides, in the Gulf of 81. Lawrence are generally concentrated during the winter in deep water of the Laurentian Channel off Southwest Newfoundland. They are dispersed during the summer, but small concentrations are found in the mouth of the S1. Lawrence River west of Anticosti Island. The fishery for this species in the Gulf increased rapidly from 1,500 tons in 1975 to nearly 9,000 tons in 1979 and declined to 3,000 tons in 1981, the catches being comprised of age-groups corresponding to those of very successful year-classes off Labrador and eastern Newfoundland. The drastic reduction in abundance since 1978, the lack of observable recruitment, the recent decline in catches, and peculiarities in certain biological characteristics indicate that substantial recruitment to the fishery in the Gulf of 81. Lawrence may come from areas outside the Gulf, possibly through the Strait of Belle Isle.

Paleomagnetic evidence for Post‐Devonian displacement of the Avalon Platform (Newfoundland)

The possibility that the Avalon Platform, where the Avalonian lithotectonic belt is best developed, was involved in late Paleozoic displacement was tested by paleomagnetic study of red sandstones of the Upper Devonian Terrenceville Formation of eastern Newfoundland. Two magnetization directions were identified by thermal demagnetization analysis of 60 oriented samples from 10 sites: a high blocking temperature, thermally discrete A component of normal and reversed polarity, and an intermediate blocking temperature, thermally distributed B component of reversed polarity. The B component (D = 185.9°, I = −3.3°, a95 = 7.2° for N = 8 sites) is interpreted as a postfolding secondary magnetization and gives a paleomagnetic pole position (latitude = 43.6°N, longitude = 117.1°E) near Early to Late Permian paleopoles for North America. The A component (D = 181.6°,I = 28.0°, a95 = 10.1° for N = 9 sites) is interpreted as the characteristic magnetization possibly dating from near the time of deposition of the Terrence ville Formation. The corresponding paleomagnetic pole position (latitude = 27.4°N, longitude = 123.5°E) falls within a group of Late Devonian‐early Carboniferous paleopoles obtained from the Acadia displaced terrain, encompassing the coastal areas of New England and the Canadian maritimes which form another part of the Avalonian belt. These paleopoles are systematically offset by 15° to 20° in latitude from coeval pole positions obtained from cratonic North America. Thus the Avalonian belt of the northern Appalachians, which is thought to represent a remnant of a Precambrian and early Paleozoic microcontinent on tectonostratigraphic considerations, appears to correspond to a late Paleozoic displaced terrain on the basis of paleomagnetic evidence.

Tidal deposits of the Lower Cambrian Random Formation, eastern Newfoundland: facies and paleoenvironments

The Avalon tectonostratigraphic zone occupies about 25% of the area of insular Newfoundland. Late Precambrian development of the Avalon terrane is distinctly different than that of other parts of the Appalachian orogen and cratonic North America. Late Precambrian volcanism and tectonic instability gave way to deposition of about 2 km of Cambrian and Lower Ordovician dominantly epiclastic sediments on a slowly subsiding, relatively stable shelf platform.The Lower Cambrian Random Formation is part of the platformal sequence and is bounded by regional disconformities over much of the Newfoundland Avalon Zone, except around Fortune Bay where it is underlain by older terrestrial and shallow-marine sediments. The Random Formation was deposited during a time of global sea-level rise, and consists of up to 250 m of shoreline, nearshore, and open-shelf deposits that record macrotidal conditions and periodic storm activity. Cross-bedded quartzarenites occur in units to about 50 m thick (one exceptional unit is 110 m thick) that tend to have gradational bases and abrupt tops. Bimodal–bipolar paleocurrent data are best explained by reversing tidal currents. These sandstone units show no evidence of intertidal (beach) processes and are therefore interpreted as subtidal ridges or shoals. The intertidal environment is represented by a shaly unit, with thin sandstone beds, that is characterized by flaser and lenticular bedding, oscillation (wave) ripples, some flat-topped ripples, and abundant synaeresis (dehydration) cracks. A muddy shoreline and subtidal sands suggest a macrotidal setting.Storm deposits range from: (1) fine, micaceous, red sandstones with fiat, gently dipping lamination, low-angle truncation surfaces, rare hummocks, shale-clast horizons, granule lags, and steep-sided erosional gulleys believed to represent lower shoreface rip-current channels; to (2) mudstones with graded, sole-marked, glauconitic sandstone beds deposited on an open shelf by storm-generated density currents.

Microsporogenesis in Larix laricina

Microsporogenesis was studied in Larix laricina in eastern Newfoundland at weekly intervals from October to April in four successive seasons. Male strobili were fixed in a 3:1 ethanol – propionic acid mixture, stained in alcoholic carmine, and squashed in 45% acetic acid.Pollen mother cells began development from interphase in early October and passed through leptotene, zygotene, and pachytene by mid-November. They remained in diplotene until mid-March to early April when meiosis was completed over a 2-to 4-week period. Microspores were produced by early May. The pattern of meiotic divisions, their duration, and variability within and between trees in L. laricina was similar to those reported for L. decidua, L. kaempferi, L. sibirica, and L. eurolepis.Deviation from the normal pattern occurred infrequently. In six trees the "resting diplotene" of winter was interrupted on one occasion and some male strobili had a "delayed meiosis" which occurred several days after meiosis in all other sampled strobili. Abnormal chromosome separations were observed on a few occasions; these consisted mostly of lagging chromosomes, a common abnormality in Larix meiosis. The implications for pollen development and seed yield are discussed.La microsporogénèse chez Larix laricina dans l'est de Terre-Neuve a été étudiée à intervalles hebdomadaires d'octobre à avril, pendant quatre années successives. Les strobiles mâles étaient fixés dans un mélange 3 : 1 d'éthanol – acide propionique, colorés au carmin alcoolique et écrasés dans l'acide acétique 45%.

Timing of arrival of the Avalon Zone in the northeastern Appalachians: a new look at the Straddling Granite

The "Straddling Granite" was previously thought to straddle the Hermitage Bay – Dover fault system, which marks the boundary between the Avalon and Gander Zones of eastern Newfoundland, and hence to fix the earliest juxtaposition of these two zones before 504 ± 12 Ma. More detailed investigation shows that these rocks are divisible into two distinct geochemical suites, the Indian Point Granite to the west and the Hardy's Cove intrusive suite to the east. Of the samples that provided the 504 Ma isochron, five were obtained from the Hardy's Cove suite and one from within the fault zone; hence the isochron must be taken as representing only a typical date for plutonic rocks within the Avalon Zone. The Indian Point Granite intrudes the Gaultois Granite, dated at 350 ± 18 Ma, and is thus considerably younger than the Hardy's Cove suite. These observations now allow for juxtaposition of the Avalon and Gander Zones to have been as late as Early Carboniferous.

Prediction of Egg Development and Mortality Rates in Capelin (Mallotus viliosus) from Meteorological, Hydrographic, and Biological Factors

We studied the factors governing in situ egg development and mortality rates in beach spawning capelin (Mallotus villosus). Time to hatching was strongly influenced by the average incubation temperature which varied between years and between cohorts in a single year, and between positions on the beach (high, mid, low tide zone). Average incubation temperatures were determined by a complex of variables which included water temperature, maximum and minimum air temperature, and hours of sunlight. Mortality rates were both spatially and temporally variable. Over 70% of the temporal and spatial variance in egg mortality was attributed to the interacting effects of egg density, water temperature, maximum and minimum air temperature, hours of sunlight, rainfall, and tidal amplitude. Multivariate equations for predicting egg mortality as a function of these variables are given. The principal climatic and hydrographic variables influencing egg mortality vary only slightly over a 7° range of latitude encompassing the main spawning sites of the eastern Newfoundland and southern Labrador coasts. The potential thus exists for synchronous year to year changes in egg mortality over this spawning range as a result of annual variations in climate and hydrographic conditions. Such synchronous changes may contribute to the substantial year to year fluctuations in capelin year-class strength.Key words: capelin, Mallotus viliosus; development, mortality, meteorology, hydrology, temperature, intertidal zone, year-class, egg, beach spawning

Peatlands of eastern Newfoundland: distribution, morphology, vegetation, and nutrient status

The peatlands of eastern Newfoundland are classified into six morphological types: domed bog, blanket bog, slope bog, basins bog, ribbed fen, and slope fen. The separation of types is based on peat depth, surface physiognomy and slope, underlying basin or slope morphology, botanical constituents, and degree of humification of the peat strata. Low elevation aerial oblique photographs and stratigraphical profiles of the six representative morphological peatland types are presented.The peatland vegetation is classified into eight associations and four pool communities; three alliances are also proposed and comparisons with syntaxonomical classifications of European peatlands are discussed. Phytosociological tables are presented for the dry bog vegetation, wet bog vegetation, and fen vegetation; a summary table showing differential species groups of each syntaxon is also presented. pH and total contents of nitrogen, calcium, and iron are determined for the major vegetation types.

THE FOODS OF GREAT AND SOOTY SHEARWATERSPUFFINUS GRAVISANDP. GRISEUSIN EASTERN CANADIAN WATERS

SummaryThe foods of Great and Sooty ShearwatersPuffinus gravisandP. griseusare described from birds collected off eastern Canada. There was a broad overlap in diet, but Great Shearwaters tended to take more squid and tough‐bodied fish such as mackerelScomber scombruswhile Sooties took more euphausiidsMeganyctiphanes norvegicaand soft‐bodied fish such as HerringClupea harengus. These differences are apparently related to differences in bill structure and in the degree of adaptation to underwater swimming.The birds appeared to feed opportunistically on whatever prey was locally available in the size‐range between euphausiids and small fish and squid:Meganyctiphanesoff southwest Nova Scotia, spawning and post‐spawning capelinMallotus villosusoff eastern Newfoundland, and migrating squidIllex illecebrosuson the Grand Bank. Possible factors influencing prey selection are discussed. It is suggested that the timing and routes of the birds' migrations in the North Atlantic are related to the exploitation of such local concentrations.Despite the overlap in diets, differences in the distributions of the two species rule out the possibility of significant competition for common food resources.

Dynamic melting of proterozoic upper mantle: Evidence from rare earth elements in oceanic crust of Eastern Newfoundland

Rare Earth Element (REE) data confirm earlier suggestions from major and trace elements that the Proterozoic Burin Group in the southwestern Avalon Zone is similar to modern oceanic tholeiites, and also exhibit a systematic evolution through the sequence. The Group forms a 60-km long belt consisting of four formations of pillowed basalt, two of subaqueous volcaniclastic and minor stromatolitic sediments and pyroclastics, and a thick gabbro-quartz diorite sill, with a total thickness of about 5000 m. Basalts of the oldest formation are enriched in light (LREE) with a chondrite-normalized pattern similar to alkali basalts. REE patterns through the rest of the sequence can be matched by those of modern ocean basins, with a steady decrease in total REE and a distinct depletion in LREE at the top of the sequence. REE patterns of the gabbroic sill are similar to those of oceanic gabbros, with LREE depletion and a small positive Eu anomaly. This evolutionary pattern can be interpreted as the result of progressive ‘dynamic’ partial melting and depletion of a single mantle source region.

Distribution of winter-developing Simuliidae (Diptera), in Eastern Newfoundland

The distribution of larval Prosimulium mixtum, Stegopterna mutata, Cnephia ornithophilia, and Simulium vittatum are discussed in relation to temperature, pH, stream order, stream origin, current velocity, and time. The influence of microcurrents and larval density on P. mixtum and St. mutata are discussed. The distribution along the stream bed changed with time. The data suggested that with these two species the spacing of the larvae and changes in microcurrent preferences displaced the population downstream as development proceeded, although other factors may play a role in the displacement. The distribution of the other two species was closely tied to the oviposition sites at lake outlets and showed little displacement with time. It is also suggested that competition between simuliids occurs although further research will be required.

A new species of Psammonyx (Crustacea, Amphipoda, Lysianassidae) from the Northwestern Atlantic

Psammonyx terranovae n.sp., distinguished from P. nobilis in the lack of ventral setae on the anterior coxal plates, is described and figured in detail. A diagnosis of the genus Psammonyx is presented. Psammonyx terranovae has been found in the intertidal in eastern Newfoundland and in the subtidal, south to the Nova Scotia banks. Its distribution is discussed in relation to its temperature tolerances and its possible past history.

Proterozoic tectonics of northwestern gondwanaland: New evidence from eastern newfoundland

Recent studies have shown that the southern Burin Peninsula, in the Avalon Zone of eastern Newfoundland, is underlain by the following stratigraphie sequences: clastic sediments derived from subaerial acidic volcanic and high-level plutonic rocks; a conformably overlying submarine basaltic assemblage with alkalic affinities at the base but dominated by tholeiite low in K, Ti, and P, with intermittent occurrences of stromatolitic limestone; unconformably overlying bimodal (tholeiite to alkalic) basalt—rhyolite erupted in a subaerial environment; conformably overlying shallow water clastic sediments ranging from Infracambrian to Middle Cambrian in age. This succession indicates a Proterozoic tectonic history of prolonged continental extension and local rupturing, with eventual stabilization during the Paleozoic. Such a tectonic model applies equally well to the late Precambrian—Lower Paleozoic rocks of Gondwanaland throughout the North Atlantic region, and may account for the sporadic occurrences of ophiolitic rocks such as those of Anglesey, southern Brittany, and northwest Africa, and other possible correlatives of the Iberian Peninsula and the Lizard Peninsula of southwest England.

Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities

The Colliers Peninsula, a typical area in the western part of the Harbour Main Group in eastern Newfoundland, is underlain by three steeply-dipping sequences of ash-flow tuffs 250–500 m thick, separated by clastic sediments, conformably overlain by subaerial mafic flows and cut by small bodies of high-level intrusive rocks rich in plagioclase phenocrysts. All rocks are of low metamorphic grade.The two lower pyroclastic sequences have a bulk composition of rhyolite and alkali rhyolite; they contain phenocrysts of albite, quartz, and biotite. Na/K ratios are highly variable; the albite crystals may be pseudomorphous after anorthociase. The upper sequence, rhyodacitic in bulk composition, has lower Si and higher Na; it lacks quartz and biotite phenocrysts but contains small amounts of calcic augite and altered olivine. The mafic flows (50% SiO2) show high Al and alkalies and low Ca and Ti. The porphyritic intrusives have 60–65% SiO2, but their bulk chemistry is otherwise similar to that of the ash-flow tuffs.The present composition of the rocks reflects complex chemical adjustments, both contemporaneous with and subsequent to the magmatic event. However, mineralogical and chemical data and trends considered to be a part of the original magmatic heritage are consistent with suggestions that the western (probably lower) part of the Harbour Main volcanic pile was formed in a continental, extensional tectonic environment.

A pattern of forest types on ribbed moraines in eastern Newfoundland

A distinctive pattern of forest types has been observed on ribbed moraines of the Avalon Peninsula, Newfoundland. This previously unreported pattern is interesting in that the best forests occur on the exposed tops and the theoretically less favourable north slopes. On each moraine, the south slopes characteristically had an uncommercial forest of balsam fir (Abiesbalsamea (L.) (Mill.)) and black spruce (Piceamariana (Mill.) BSP.), the top and upper north slopes had a forest of white birch (Betulapapyrifera Marsh.) and balsam fir, and the lower north slope had a pure balsam fir forest. Site descriptions are provided for each forest type and the vegetation succession following fire is proposed.

Significance of fossiliferous Middle Cambrian rocks of Rhode Island to the history of the Avalonian microcontinent

Middle Cambrian trilobites of Acado-Baltic affinities have been found in southern Narragansett Bay, Rhode Island, in phyllites previously mapped as part of the Pennsylvanian stratigraphy of the Narragansett Basin. The trilobite-bearing phyllites form the basal unit of an approximately 1-km-thick sequence that has undergone four episodes of folding and cleavage formation. Three different trilobites are represented. Badulesia tenera (Hartt), which gives a diagnostic medial Middle Cambrian age, is also known from New Brunswick, eastern Newfoundland, southern Germany, northern Spain, and eastern Turkey. This species in northern Spain characterizes a subzone within the Middle Cambrian Badulesia zone correlating approximately with the lower part of the Paradoxides paradoxissimus zone of northern Europe. Nearby in Newport, Rhode Island, a sequence of maroon and green clastic sediments rests unconformably on Precambrian igneous rocks and sediments. If these should be proven to be Lower Cambrian, this succession in southern Narragansett Bay would be the most complete Cambrian succession yet recognized in southern New England and possibly a nearly complete record of sedimentation for this area for the entire Cambrian Period. These well-exposed rocks are part of a distinctive succession of upper Precambrian and lower Paleozoic rocks and are interpreted as a fragment of the Avalonian platform or microcontinent, closely related to rocks of the eastern margin of the northern Appalachians and the western margin of western Europe.

Aborted Proterozoic rifting in eastern Newfoundland

Recent geological mapping and geochemical studies of the late Proterozoic rocks of the Burin Peninsula in the southwestern part of the Avalon Zone of Newfoundland show the following sequence: (1) The basal Rock Harbour Group, a sedimentary assemblage ranging from conglomerates to turbidites, was derived from a subaerial volcanic–plutonic source region. (2) The overlying Burin Group, a belt of mafic volcanic and intrusive rocks that have alkalic affinities at the base but are dominated by oceanic tholeiite. (3) The Marystown Group, a bimodal sequence of alkalic basalts and rhyolites deposited in a subaerial environment unconformably above the Burin Group, and apparently conformably overlain by Infracambrian to Cambrian sedimentary rocks. Stromatolites occur within resedimented limestone breccias and conglomerates at the top of the Rock Harbour Group and throughout the Burin Group.These assemblages are interpreted to indicate that after a period of continental type bimodal volcanism, the Avalon terrain was rifted in Burin Group times to form some kind of small ocean basin, which was abruptly closed with a reversion to continental type bimodal volcanism of the Marystown Group.

Geomagnetic sounding near the northern termination of the Appalachian System

A general survey of geomagnetic induction phenomena in Newfoundland is undertaken. The northeastward extension of the 'Atlantic' conductivity anomaly can be traced into southwestern Newfoundland where it is lost in intense conduction–induction effects due to the channeling of shallow water electric currents about the projecting corner of southeastern Newfoundland. Shallow water induction processes in the Gulf of St. Lawrence are better clarified. Evidence is presented for a tentative inland conductivity anomaly in eastern Newfoundland where geological evidence points to an ancient zone of subduction.

Palaeomagnetism of middle Ordovician volcanic rocks from Quebec

This palaeomagnetic study is centered on agglomerates and volcanic rocks from the western margin of the Appalachian belt in the Drummondville-Actonvale-Granby area, Quebec (long.: 72°30′W, lat.: 46°00′N). It involves a total of 36 oriented samples (111 speciments) distributed over eleven sites. Both thermal and AF cleaning techniques were used to isolate residual remanent components. The dispersion of the directions is slightly reduced after AF cleaning and thermal treatment. The palaeopole position obtained is 191°E, 6°N ( d m = 14°, d p = 7°) after thermal treatment and 164°E, 19°N ( d m = 11°, d p = 6°) after AF cleaning. The polarity of most of the sites (two exceptions) are reversed. The thermal-treated data appear to be relatively stable and an approximate value of the primary magnetization is extracted from them. The palaeopole obtained does not lie close to the tentatively defined position of the Cambrian and Ordovician poles from rocks of the North American plate; it is located near the Upper Cambrian and Lower Ordovician poles from eastern Newfoundland and the Lower Ordovician pole from the Caledonides in Europe.

Early Cambrian algae croppers

Conical, calcareous tubes and worm burrows in Lower Cambrian stromatolites in eastern Newfoundland are found associated with indications of grazing activity. Cropping by early herbivores may have reduced the degree of dominance of the existing stromatolite-constructing algae, allowing diversification of new groups. Stromatolites, so plentiful in Precambrian and early Cambrian time, slowly perished and at present are limited only to specific environments. The cause of this drastic reduction was probably the activity of cropping, grazing, and burrowing animals.

The geochronology of some granitic bodies from eastern Newfoundland and its bearing on Appalachian evolution

Whole-rock Rb–Sr isochron ages from nine granitic plutons that intrude the Central Mobile Belt and the Avalon Zone of Newfoundland are consistent with the view that most of the magmatic activity for this segment of the Appalachian Orogen is related to the Acadian Orogeny. Most of the granites are between 400 Ma and 340 Ma old, although two from the Avalon Zone are significantly different. One, the foliated Swift Current granite, is late Cambrian – early Ordovician (500 ± 30 Ma), whereas the other, the peralkaline St. Lawrence granite, is Carboniferous (315 ± 5 Ma).Several foliated granites from the Gander Zone of the Central Mobile Belt, formerly considered to be older than Mid-Ordovician, are Silurian or Devonian in age. Five megacrystic biotite granites have ages ranging between 420 ± 20 Ma and 340 ± 10 Ma, and a leucocratic granite, the Middle Ridge Pluton, gives an age of 370 ± 15 Ma. None of the granites from the Gander Zone is older than 420 ± 20 Ma, and geochronological evidence for a Precambrian basement in the Central Mobile Belt has still to be found.The initial 87Sr/86Sr ratios show no correlation with age, although the initial ratio of 0.722 for the St. Lawrence granite is much higher than the ratios of between 0.704 and 0.709 for the other granites; this high ratio is consistent with derivation of the granite by partial melting of the continental crust.The isotopic data impose certain constraints on models proposed for the evolution of Newfoundland, the most important being: (i) extensive Devonian magmatism; (ii) intense post-400 Ma cataclasis; (iii) generation of petrographically similar granites at different times; and (iv) Carboniferous magmatism.