Northern Baffin Island Research Articles

The Steensby Inlet Ice Stream in the context of the deglaciation of Northern Baffin Island, Eastern Arctic Canada

AbstractDeglaciation of northern Baffin Island involved several large ice streams with contrasting histories. Three north‐flowing, marine‐based ice streams were in place during the Last Glacial Maximum, but they retreated at widely varying rates during the early and middle Holocene. The Steensby Inlet Ice Stream formed in response to over‐steepening of the ice front during deglaciation of Foxe Basin. It caused an abrupt change, in places a general reversal, of flow about 6 ka BP and operated across its full width for only about 500 years. Nevertheless, it left a distinct subglacial footprint, including an hourglass shaped bedform set. A dense network of till samples from the region of the ice stream reveals a sharp‐sided, pluglike dispersal of carbonate debris that was sustained by erosion in the source area of about 5 mm a−1. The ice stream devolved into valley‐controlled ice streams separated by cold‐based ice over interfluves. The former evacuated debris along valleys and left erosional till scarps along the sides of sliding ice. Post‐ice‐stream end moraines, including the large Gifford Moraine, require later cold‐based flow across the drumlins formed by the ice stream. Copyright © 2008 John Wiley & Sons, Ltd.

A millennial perspective on Arctic warming from 14C in quartz and plants emerging from beneath ice caps

Observational records show that the area of ice caps on northern Baffin Island, Arctic Canada has diminished by more than 50% since 1958. Fifty 14C dates on dead vegetation emerging beneath receding ice margins document the persistence of some of these ice caps since at least 350 AD. In situ cosmogenic 14C in rock surfaces, and 14C in plant macrofossils from lake‐sediment cores demonstrate that the plateau remained ice‐free through the middle Holocene, but has supported ice caps for more than 2000 of the past 2800 years. The rapid disappearance of these ice caps over the past century, despite decreasing summer insolation, further demonstrates the unusual character of 20th Century warmth. Widespread ice‐cap expansion ∼1280 AD early in the Little Ice Age, and intensified expansion ∼1450 AD, coincide with peak stratospheric volcanic aerosol loading and reduced solar luminosity, suggesting that these mechanisms may have initiated ice‐cap growth, subsequently maintained by strong positive feedbacks.

Mineral-Potential Mapping for MVT Deposits with Limited Data Sets Using Landsat Data and Geological Evidence in the Borden Basin, Northern Baffin Island, Nunavut, Canada

Posterior probabilities of occurrence for Zn-Pb Mississippi Valley Type (MVT) mineralization were calculated based on evidence maps derived from regional geology, Landsat-TM, RADARSAT-1, a digital elevation model and aeromagnetic data sets in the Borden Basin of northern Baffin Island, Canada. The vector representation of geological contacts and fault traces were refined according to their characteristics identified in Landsat-TM, RADARSAT-1, DEM, slope, aspect, and shaded relief data layers. Within the study area, there is an association between the occurrence of MVT mineralization and proximity to the contact of platformal carbonates and shale units of the adjacent geological formation. A spatial association also tends to exist between mineralization and proximity to E-W and NW-SE trending faults. The relationships of known MVT occurrences with the geological features were investigated by spatial statistical techniques to generate evidence maps. Supervised classification and filtering were applied to Landsat-TM data to divide the Society Cliffs Formation into major stratigraphic subunits. Because iron oxides have been observed at some of the MVT occurrences within the Borden Basin, Landsat-TM data band ratio (3/1) was calculated to highlight the potential presence of iron-oxides as another evidence map. Processed Landsat-TM data and other derived geological evidence maps provided useful indicators for identifying areas of potential MVT mineralization. Weights of evidence and logistic regression were used independently to integrate and generate posterior probability maps showing areas of potential mineralization based on all derived evidence maps. Results indicate that in spite of the lack of important data sets such as stream or lake sediment geochemistry, Landsat-TM data and regional geological data can be useful for MVT mineral-potential mapping.

Temporal Trends of Perfluoroalkyl Contaminants in Polar Bears (Ursus maritimus) from Two Locations in the North American Arctic, 1972−2002

Perfluoroalkyl substances are globally distributed anthropogenic contaminants. Their production and use have increased dramatically from the early 1980s. While many recent publications have reported concentrations of perfluorooctane sulfonate (PFOS) and other perfluoroalkyl acids (PFAs) in biotic and abiotic samples, only limited work has addressed temporal trends. In this study we analyzed archived polar bear(Ursus maritimus) livertissue samples from two geographic locations in the North American Arctic, collected from 1972 to 2002. The eastern group, taken from the vicinity of northern Baffin Island, Canada, comprised 31 samples, and the western group, from the vicinity of Barrow, Alaska, comprised 27 samples. Samples were analyzed for perfluorocarboxylic acids (PFCAs) from carbon chain length C8 to C15, perfluorohexane sulfonate, PFOS, the neutral precursor perfluorooctane sulfonamide (PFOSA), as well as 8:2 and 10:2 fluorotelomer acids and their alpha,beta unsaturated acid counterparts. Concentrations of PFOS and PFCAs with carbon chain lengths from C9 to C11 showed an exponential increase between 1972 and 2002 at both locations. Doubling times ranged from 3.6 +/- 0.9 years for perfluorononanoic acid in the eastern group to 13.1 +/- 4.0 years for PFOS in the western group. PFOSA showed decreasing concentrations over time at both locations, while the remaining PFAs showed no significant trends or were not detected in any sample. The doubling time for PFOS was similar to the doubling time of production of perfluoroctylsulfonyl-fluoride-based products during the 1990s.

Ultrasonic tracking of Greenland sharks, Somniosus microcephalus, under Arctic ice

Six Greenland sharks, Somniosus microcephalus (Bloch and Schneider, 1801), 190–355 cm fork length, were tracked under land-fast sea ice off northern Baffin Island (73.2°N; 85.3°W) between 16 and 28 May 1999, using ultrasonic telemetry. The sharks were tracked continuously for periods of 5.5–13.0 h, with the tracks of two individuals lasting 31.4 and 42.8 h, respectively, each with an interval when the track was lost. Several sharks dove after release and moved along the ocean bottom for the duration of the tracking period, while others varied their movements regarding course and depth. Two sharks made repeated visits to within 11 m of the ice–water interface from deeper water. The tracked sharks exhibited no apparent depth or temperature preferences, and pooled data indicated that sharks remained deep during the morning and gradually moved into shallower depths through the afternoon and night. Rates of descent (average=0.099 m s−1) were significantly greater than rates of ascent (average=0.058 m s−1) for all sharks, and the average rate of horizontal movement over ground was estimated as 0.215 m s−1. Based on the movements of tracked sharks and information contained in the literature, S. microcephalus may prey on seals in areas covered by land-fast sea ice.

Geologic and Geochronologic Constraints on the Timing of Mineralization at the Nanisivik Zinc-Lead Mississippi Valley-Type Deposit, Northern Baffin Island, Nunavut, Canada

The Nanisivik mine is located on Borden Peninsula, northern Baffin Island, about 750 km north of the Arctic Circle. The deposit is hosted by Mesoproterozoic sedimentary rocks of the Bylot Supergroup that rest unconformably on the Mary River Group, an Archean to Proterozoic basement complex of granites and gneisses. The Mesoproterozoic strata have been folded into broad, open folds with north-south–trending axes. The sulfides at Nanisivik are hosted in petroliferous dolostones of the Society Cliffs Formation. A series of long-lived, east-west–trending, normal faults divide the Nanisivik area into a series of horst and grabens. All known sulfide bodies are associated with normal faults, particularly where they cut the fold axes of antiforms. The geometry of the main sulfide body indicates that sulfides were emplaced after tilting and folding of the host strata and that a horizontal feature such as a gas-water interface controlled the precipitation of the sulfides. The sulfides show no displacement across the Keystone fault, although the fault has displaced the host stratigraphy by about 150 m and has displaced the Mine dike, a Franklin-aged intrusion (~723 Ma), by about 40 m with steep oblique-slip movement. A progressive potassium feldspar alteration selvage, about 3 m wide, on the margin of the Mine dike has been recognized. Textural evidence and immobile element ratios indicate that this is an alteration product of the dike, interpreted to have formed by the hydrothermal event that emplaced the sulfides. Similar alteration assemblages are present throughout the mine and are interpreted to be altered siliciclastic sedimentary rocks. The 40 Ar- 39 Ar ages of orthoclase from these alteration assemblages indicate a Middle Ordovician (461 Ma) age of mineralization. Although the regional process that resulted in the formation of the Nanisivik deposit remains unclear, it is possible that topographically driven fluid may have resulted from localized Middle Ordovician uplift in the region, as seen at the Navy Board High. Basinal brines may have migrated along the basement contact within the overlying Mesoproterozoic siliciclastic sedimentary rocks, and local basement topography, such as the horst and graben structures, may have focused fluid flow into the Society Cliffs Formation at Nanisivik. Local structural and stratigraphic traps would ultimately have localized and controlled the precipitation of the sulfides.

Geologic and Geochronologic Constraints on the Timing of Mineralization at the Nanisivik Zinc-Lead Mississippi Valley-Type Deposit, Northern Baffin Island, Nunavut, Canada

Geologic and Geochronologic Constraints on the Timing of Mineralization at the Nanisivik Zinc-Lead Mississippi Valley-Type Deposit, Northern Baffin Island, Nunavut, Canada

Graham Westbrook Rowley (1912-2003)

Most readers of Arctic will have heard with sadness the news of Graham Rowley's death in Ottawa on December 31, 2003. And many will have read with gratitude the heartfelt tributes his passing occasioned in the press on both sides of the Atlantic, which variously detailed Graham's lifelong, wonderfully eclectic engagement with the Canadian Arctic through exploration, administration, scholarship, and scientific enterprise. Graham's introduction to the Arctic came in 1936. ... he seized the chance to join Tom Manning's British Canadian Arctic Expedition (1936-39), which was headed for northern Baffin Island and the largely unexplored east coast of Foxe Basin. ... As the expedition's archaeologist, Graham had one main quest, set for him by Diamond Jenness at the National Museum in Ottawa: to unearth conclusive evidence of an ancient Arctic culture quite distinct from the so-called Thule culture described by Danish archaeologist Therkel Mathiassen. ... At Avvajja, [near Igloolik Island] he was able to excavate a uniquely site, confirming Jenness's hunch, and establishing the Dorset culture as archaeological fact. He published the results of his archaeological investigations in an article entitled Dorset Culture of the Eastern Arctic, which appeared in the American Anthropologist (New Series 42, 1940). ... The British Canadian Arctic Expedition left its mark on Igloolik's recorded oral history. Graham and Reynold Bray (who tragically drowned in September 1938) are especially remembered. They both had Inuktitut names, Graham being Makkuktu'naaq ('the little, or likeable, young man'), and Reynold, Umiligaarjuk ('the little bearded one'). A mixture of surprise, amusement, and admiration had greeted their arrival in Igloolik by dog team in February 1937. Here were two young white men, remarkably ill-dressed, lice-infested, walking on the shanks of their skin boots, and almost out of supplies, who had journeyed more or less alone from Repulse Bay, some 200 miles away, in the middle of winter. Even more remarkably, they knew how to manage a dog team, build snow houses, and (especially Graham) communicate in basic Inuktitut. Inuit elders interviewed in Igloolik during the 1990s still remembered Graham's departure for the war and the doubts they had entertained at the time about his chances of survival. But survive he did. Graham returned to Ottawa after the war. Still serving in the Canadian Army, he commanded the advance party of Exercise Musk-Ox, an operation designed to test the effectiveness of motorized vehicles in the Arctic and Subarctic regions of Canada. The assignment took him from Churchill, Manitoba, across the barrens by tractor-train to Baker Lake. Retiring from the Army in 1946, he joined the Defence Research Board, where he was responsible for Arctic research. He oversaw the Board's sponsorship and support of Operation Lyon, which brought a medical research team, including Graham, to Igloolik by R.C.A.F Canso aircraft in the late summer of 1949. Needless to say, he took the opportunity to engage again in archaeological excavation, picking up where he had left off ten years previously, and uncovered some interesting Dorset and Thule material. In 1947, ... Graham and ... like-minded friends, founded the Arctic Circle Club, an Ottawa-based association that quickly became the focus for all those with northern interests. ... In 1951, Graham began his 23-year career with the Department of Northern Affairs and National Resources ..., serving first as Secretary of the Advisory Committee on Northern Development, responsible for the coordination of government activities in the North, then as Scientific Adviser. ... he was closely involved with the planning and establishment for the Eastern Arctic Scientific Resource Centre, now the Igloolik Research Centre, which opened in 1975 and, through federal and now territorial administration, has supported scientific research in northern Foxe Basin ever since. ... Graham re tired from the Public Service in 1974, .... The archaeological work of Graham's daughter Susan on Igloolik Island, which spanned a decade beginning in the mid-1980s, happily gave Graham the opportunity to return frequently to his old haunts. ... Graham's professional achievements were widely acknowledged: investiture in the Order of Canada, honorary doctorates from Carleton Univesity and the University of Saskatchewan, the Massey Medal of the Royal Canadian Geographical Society, and the Northern Science Award, to name a few. He was also a past Chairman of the Arctic Institute of North America. ...

Geochemistry of a 1.2 Ga carbonate-evaporite succession, northern Baffin and Bylot Islands: implications for Mesoproterozoic marine evolution

A 4‰ positive shift in the carbon isotopic composition of the oceans, recorded globally in marine carbonate rocks at ∼1.3 Ga, suggests a significant change in Mesoproterozoic carbon cycling. Enhanced burial fluxes of organic carbon, relative to inorganic carbon, implied by this isotopic shift may have resulted in increased oxygenation of the Earth's biosphere, as has been suggested for similar Paleoproterozoic and Neoproterozoic carbon isotope events. This hypothesized Mesoproterozoic oxygenation event may be recorded in the geologic record by the appearance of the oldest preserved, laterally extensive, bedded marine CaSO 4 evaporites in the ∼1.2 Ga Grenville and Bylot supergroups. Speculation that the appearance of extensively preserved marine gypsum and/or anhydrite reflects increased biospheric oxygenation has been challenged, however, by the hypothesis that CaSO 4 precipitation prior to the Mesoproterozoic may have been inhibited by significantly higher marine carbonate saturation, which would have facilitated carbonate precipitation and effectively limited Ca 2+ availability during seawater evaporation (Grotzinger, J.P., 1989. Controls on Carbonate Platform and Basin Development, vol. 44, SEPM, Tulsa, OK, pp. 79–106), regardless of O 2 levels. The 1.2 Ga Society Cliffs Formation (Bylot Supergroup, northern Baffin Island) consists of ∼720 m of peritidal carbonates, evaporites, and minor siliciclastic rocks. Evaporites occur predominantly in the lowermost 300 m of the Society Cliffs Formation, where gypsum beds (1–250 cm thick) constitute up to 15% of the exposed strata. Stratigraphic and sedimentologic constraints, as well as isotopic (C, O, Sr) and elemental (Ca, Sr, Na, K, Ba) compositions of evaporites and associated carbonates, indicate a marine origin for Society Cliffs gypsum. An upsection increase in δ 34S of Society Cliffs gypsum (from +22‰ to +32‰ VCDT) is therefore interpreted to reflect primary variation in Mesoproterozoic marine sulfate compositions, although the inferred rapidity of isotopic change requires a marine sulfate reservoir significantly smaller than that of the modern ocean. Examination of the maximum fractionation between coeval sulfide and sulfate reservoirs, however, indicates that Mesoproterozoic oceans were not sulfate-limited with respect to bacterial sulfate reduction either before or after the hypothesized 1.3 Ga oxygenation event. Although increased ocean-atmosphere oxygenation may have increased marine sulfate concentrations at this time, the exact role of a Mesoproterozoic oxygenation event cannot be ascertained. Furthermore, high Mg/Ca ratios measured in Society Cliffs gypsum suggest that elevated Mg 2+ concentrations in Proterozoic marine systems may have helped sustain carbonate hypersaturation, and that Ca 2+-limitation may have played a significant role in the Proterozoic record of evaporite deposition.

Hints of Frequent Pre-Columbian Contacts

ARCHAEOLOGYLast week's opening of the Smithsonian Institution's exhibition, Vikings: The North Atlantic Saga, served to popularize the scientific evidence that the first contact between Europeans and Americans was not Columbus's voyage but Viking landfall in Newfoundland, thought to have occurred about A.D. 1000. And at a 2-day symposium, a Canadian archaeologist presented stunning new traces of the Norse on northern Baffin Island in the Canadian Arctic, at least 200 years before Columbus. Although not all her colleagues are convinced, the researcher argues that the evidence shows that in the Arctic, unlike in Newfoundland, the Norse had frequent and prolonged contact with aboriginal peoples--the first sustained close encounter of the Old World with the New.

PRECAMBRIAN METAMORPHIC AND TECTONIC EVOLUTION OF NORTHERN BAFFIN ISLAND, NUNAVUT, CANADA

The northern part of Baffin Island, in Nunavut, lies within the ca. 3.0–2.5 Ga Committee belt, characterized by episodic granitic plutonism and greenschist- to upper-amphibolite-facies belts of supracrustal rocks. Whereas the entire belt on Baffin Island was likely affected by ca. 2.7 Ga plutonism and associated metamorphism, there is also evidence of a high-grade event at ca. 2.55–2.5 Ga. Evolution of the Baffin orogen in south-central Baffin Island led to generation of the ca. 1.86 Ga Cumberland Batholith, ca. 1.85–1.83 Ga northwest-directed thrusting of the Foxe fold-and-thrust belt over the Dexterity granulite belt (DGB), and variable structural and metamorphic reworking of the Committee belt on northern Baffin Island. Thermobarometric data for granulite-facies rocks in the western DGB indicate ~8.7 kbar paleopressure, interpreted to have been achieved in continental crust thickened by thrust imbrication. Paleopressure decreases gradually northward from the western DGB to <4 kbar, but decreases sharply south of the Isortoq fault zone (IF), which approximates the southern boundary of the DGB. Combined thermobarometric and structural constraints suggest that the IF represents an important crustal-scale structure involved in both NW-directed thrusting and tectonic loading of the DGB, as well as subsequent extensional unroofing of the DGB. Southwest-directed thrusting in the ca. 1.825–1.81 Ga Northeast Baffin thrust belt (NBTB) is interpreted to have produced similar tectonic thickening and ~10.5 kbar pressures along most of the length of this belt on northern Baffin Island, including the eastern part of the DGB. The ~6–8 kbar Archean Bylot Batholith represents a higher structural level that may have contributed to tectonic loading of adjacent high-pressure rocks in the NBTB.

δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations

The Bylot Supergroup, northern Baffin Island, contains &gt;1500 m of platform, shelf, and slope carbonates deposited between ~ 1270 and ~ 723 Ma. Limited chronostratigraphic data have led to the broad correlation of the Bylot Supergroup with predominantly Neoproterozoic successions in northern and western Laurentia; yet, detailed correlation has been impossible given biostratigraphic and lithostratigraphic limitations. Carbon-isotope chemostratigraphy represents a potential dataset to constrain such interregional correlations. Carbon isotopic data from the Bylot Supergroup and broadly coeval successions from Somerset Island and northwest Greenland reveal distinct stratigraphic trends in δ13C, with intervals of moderate 13C enrichment (+3.5 ± 1‰) punctuated by excursions to slightly negative values (-1.0 ± 1‰). Although the scale of the observed variation is muted relative to Neoproterozoic standards, the dissimilarity of values to those recorded in northwestern Laurentia suggests that these strata delineate a discrete depositional interval. Comparison of isotopic values with published data indicates that δ13C values between approximately -1.0 and +4.0‰ are characteristic of the interval between ~ 1300 and ~ 800 Ma. This pattern is distinct from that of younger Neoproterozoic successions, which typically record values &gt;+5‰, and older Mesoproterozoic successions, which record values near 0‰, and suggests that these moderately positive values may be useful for broad time correlation. Compilation of new and published data permits the tentative reconstruction of a global Mesoproterozoic carbon isotopic curve.

Borden dykes of Baffin Island, Northwest Territories: a Franklin U-Pb baddeleyite age and a paleomagnetic reinterpretation

U-Pb baddeleyite geochronology for two Borden diabase dykes of northern Baffin Island gives an intrusion age of ca. 720 Ma, coeval with the age established elsewhere for the Franklin igneous event. Thus, the Borden dykes belong to the Franklin dyke swarm, rather than forming a separate swarm that intruded at ca. 950-900 Ma, as has been suggested previously on the basis of paleomagnetism and K-Ar ages. As a result, the paleopole from the Borden dykes can no longer be utilized to help constrain the ca. 1050-850 Ma Grenville Loop of the North American polar wander path. Reevaluation of paleomagnetic data for the dykes of northern Baffin Island suggests that Borden dyke magnetizations resulted from superposition of a steeply directed component of chemical remanent magnetization on normal and reversed primary Franklin components. The overprint direction is consistent with a Cretaceous-Tertiary age and is likely related to normal faulting and graben development during the opening of Baffin Bay.

Borden dykes of Baffin Island, Northwest Territories: a Franklin U-Pb baddeleyite age and a paleomagnetic reinterpretation

U-Pb baddeleyite geochronology for two Borden diabase dykes of northern Baffin Island gives an intrusion age of ca. 720 Ma, coeval with the age established elsewhere for the Franklin igneous event. Thus, the Borden dykes belong to the Franklin dyke swarm, rather than forming a separate swarm that intruded at ca. 950-900 Ma, as has been suggested previously on the basis of paleomagnetism and K-Ar ages. As a result, the paleopole from the Borden dykes can no longer be utilized to help constrain the ca. 1050-850 Ma Grenville Loop of the North American polar wander path. Reevaluation of paleomagnetic data for the dykes of northern Baffin Island suggests that Borden dyke magnetizations resulted from superposition of a steeply directed component of chemical remanent magnetization on normal and reversed primary Franklin components. The overprint direction is consistent with a Cretaceous-Tertiary age and is likely related to normal faulting and graben development during the opening of Baffin Bay.

Mesoproterozoic deep‐water reefs from Borden Peninsula, Arctic Canada

ABSTRACTA superbly exposed stromatolite reef complex occurs in the Victor Bay Formation near Strathcona River on northern Baffin Island. Individual reefs are up to 130 m thick and nearly 1 km in length, and their development was clearly related to their position in the facies spectrum and to sea‐level dynamics. In the first sea‐level cycle, metre‐scale reefs grew amongst mid‐ramp calcarenites and outer‐ramp shales during slow sea‐level rise; a 25‐m‐thick oblate reef tract, separating mid‐ramp and outer‐ramp facies, formed during the highstand. The greatest period of reef growth was during the second sea‐level cycle. Pinnacle reefs nucleated on the karsted upper surface of the oblate reef tract and aggraded rapidly in response to rising sea‐level, producing structures with more than 75 m of depositional relief. A gradual symmetrical succession of stromatolite growth forms, from stratiform to cylindrical columns to conical columns and then back through cylindrical columns to stratiform, is mirrored by evidence in offreef deposits for deepening to a maximum flooding surface and then shallowing. The tops of these high‐standing reefs were karsted during the following regression, while dolomite ‘cryptodomes’ grew as sheets on their submerged flanks and as progradational tongues extending basinward of the reefs. Continued sea‐level fall resulted in subaerial exposure of the entire reef complex and the extensive formation of surface and subsurface karst.These Proterozoic slope buildups are similar to Phanerozoic deep‐water reefs in size, shape, prevalence of synsedimentary lithification, presence of Neptunian dykes and in their well‐developed vertical zonation of reefbuilders. However, they differ in being constructed exclusively by stromatolites rather than being mud mounds with small skeletal elements, and in lacking halos of perireefal sand‐ and gravel‐sized calcareous debris. Their responses to changes in sea‐level were strikingly similar to those shown by their younger counterparts, and suggest that sequence‐stratigraphic concepts derived from studies of Phanerozoic reefs can also be applied to the Proterozoic.

Shale-Facies Microfossils from the Proterozoic Bylot Supergroup, Baffin Island, Canada

Organic-walled microfossils are reported from the Borden Rift Basin of northern Baffin Island and Bylot Island. The diverse assemblage, obtained by palynological acid maceration, comprises 39 taxa and occurs in fine-grained siliciclastic and carbonate units from all but the two lowermost formations of the Bylot Supergroup; their age is bracketed between 1,270 and 750 Ma. Of 307 samples analyzed from all parts of the basin, 133 yielded identifiable remains. The microbiota comprises the following taxa:Siphonophycus septatum, S. robustum, S. rugosumn. comb.,S. kestron, S. capitaneum, Pellicularia tenera, Polythrichoides lineatus, Obruchevella valdaica, Karamia? sp., opaque filaments,Oscillatoriopsisspp.,Palaeolyngbyasp.,Arctacellularia tetragonalan. comb.,A. ellipsoidea, Chlorogloeaopsis contextan. comb.,C. kanshiensisn. comb.,Navifusa bacillarisn. comb.,N. majensis, N. actinomorphan. comb.,Leiosphaeridia minutissima, L. tenuissima, L. crassa, L. jacutica, L. ternata, Lophosphaeridium granulatum, Valeria lophostriata, Pterospermopsimorpha insolita, Eomicrocystis elegans, E. malgica, Symplassosphaeridiumspp.,Synsphaeridiumspp.,Satka squamifera, Satkaspp.,Coneosphaera arctican. sp.,Coneosphaerasp.,Spumosina rubiginosa, andFabiformis baffinensisn. sp. The taxonPalaeocalothrix divaricatus, present in some macerates, is possibly a modern fungal contaminant. Abundance and taxonomic diversity varies considerably between formations and environments, with the Arctic Bay Formation exhibiting the greatest productivity and species diversity of the seven formations studied, and the transgressive muddy shelf deposits being the most productive of the 11 environments recognized. This microfossil assemblage of predominantly planktonic species has distinctive taxa in common with Middle to Late Riphean sequences in Siberia (Lakhanda and Miroedikha Groups, ca. 950 to 850 Ma), the lower part of the Thule Group (&lt; 1,270 Ma) in northwest Greenland, the Fury and Hecla Group in western Baffin Island, and taxa reported from the upper part of the Bushimay Supergroup in Zaire. On the other hand, some elements in the Bylot Supergroup are more characteristic of Vendian beds on the Russian Platform, indicating longer stratigraphic ranges for such taxa than previously thought. The compositional similarity between the Borden Basin and Siberian sequences supports palinspastic reconstructions juxtaposing Siberia and Laurentia during the middle to late Proterozoic, and the opening of the Poseidon Ocean.

Diving behaviour of narwhals (Monodon monoceros) on their summer grounds

Three adult female narwhals from the population that summers in the sheltered waters of northern Baffin Island, Canada, were fitted with satellite-linked UHF radio packages. The units logged and transmitted diving and swim-speed data and revealed the location of the study animals for periods of up to 19 days. Most diving activity was in the top 40 m and bottom 40 m of the water column. Shallow dives were characterized by low rates of descent and ascent (&lt;0.5 m∙s−1), short submersions, and frequent changes of vertical direction. Deep dives were normally to, or near to, the seabed in depths of up to 257 m, and involved both faster rates of vertical movement (1–2 m∙s−1) and longer periods underwater (up to 15.1 min). Midwater dives were intermediate in all respects. Deeper dives were of a characteristic "square" profile and provided an average of 7 min at the chosen depth, representing 57% of the time submerged. No dives were demonstrably longer than the estimated aerobic dive limit for this species. Activity at depth, including rapid swimming and many changes of vertical direction, was indicative of foraging and consistent with a diet of many small prey items. Overall, a relatively small proportion of time was devoted to presumed foraging activity, suggesting either that feeding is a low priority at this time of year or that the whales' nutritional needs could be easily met by the food stocks available.

Multistage dolomitization in the Society Cliffs Formation, northern Baffin Island, Northwest Territories, Canada

Dolostones of the Upper Proterozoic Society Cliffs Formation on northern Baffin Island are host to the Nanisivik lead–zinc sulfide deposits. Two distinct stages of dolomitization have occurred, distinguished by their petrographic, cathodoluminescence, and isotopic characteristics: (1) massive dolomitization of precursor carbonates, and (2) late-stage cementation. Sabkha facies of the lower member of the formation and laminated algal stromatolitic to massive dolostones of the upper member are isotopically similar: δ18O ranges from −1.5 to −6.5‰; δ13C from +1.7 to +3.1‰ PDB; and 87Sr/86Sr averages 0.70761. Petrographic and geochemical evidence indicates that these dolostones formed chiefly by seawater thermal convection beneath shale of the overlying Victor Bay Formation, although mixing of meteoric and marine water also could have occurred. Later fracture-filling dolomitic cements have consistently lower δ18O, but δ13C is similar to that in the host dolostones. Microtraverses of single fractures filled with dolomitic cements show progressive δ18O depletion through time; the last (innermost) generation is correlated with sparry gangue in the ore deposits and also has lower δ13C with respect to the Society Cliffs dolostones, due to mixing of bicarbonate produced from sulfate reduction. The cement was precipitated from warmer fluids, with partial replacement of earlier dolomite. Dolomitizing fluids responsible for later fracture and vug-filling cements may have been released by compaction of the underlying Arctic Bay shales, which also appears to have been the source of the base metals.

The Numbers and Distribution of Greater Snow Geese on Bylot Island and near Jungersen Bay, Baffin Island, in 1988 And 1983

We conducted aerial photographic surveys of greater snow geese on portions of Bylot Island and northern Baffin Island during August 1988 to determine whether changes had occurred since a similar survey in 1983. On the 1600 sq/km south plain of Bylot Island, using a quadrat system and stratified random sampling, we estimated a population of 26,300 breeding adults, 5,400 failed- and non-breeding adults, and 41,400 goslings; the breeding component had increased by 58% from the 1983 survey. In a 274 sq/km study area in Jungersen Bay on northern Baffin Island, we conducted total counts and recorded 2,555 adult breeders, 546 failed- and non-breeders, and 4,127 goslings; the breeding segment had declined by 15% since 1983. The later date of the survey in 1988, relative to that of 1983, is believed to have been the main cause of a more even distribution of broods among strata on Bylot Island and may have contributed to an underestimation of breeding geese at Jungersen Bay. Both survey areas supported high densities of breeding greater snow geese in both years. Bylot Island supported a similar proportion of the entire greater snow goose breeding population in 1988 (13%) and 1983 (15%).Key words: Anser caerulescens atlanticus, Baffin Island, breeding distribution, Bylot Island, Canada, goose surveys, greater snow goose

Organochlorine contaminants in narwhal ( Monodon monoceros) from the Canadian Arctic

Organochlorine pesticides (DDT, chlordane, polychlorinated camphenes (PCCs), dieldrin, hexachloroheclohexanes (ΣHCH), mirex), polychlorinated biphenyl congeners (PCBs) and chlorobenzenes (ΣCBz) were determined in blubber and liver of narwhal ( Monodon monoceros) collected during 1982–1983 from Pond Inlet on northern Baffin Island in the Canadian Arctic. PCCs were the predominate organochlorines in narwhal blubber, ranging in concentration from 2990 to 13 200 ng g −1 (wet wt) in males and from 1910 to 8390 ng g −1 in females. PCCs consisted of two major components, an octachlorobornane and a nonachlorobornane with gas chromatographic retention times of 1·05 and 1·22, relative to 4,4′-DDE. ΣPCB concentrations in blubber ranged from 2250 to 7290 ng g −1 in males and from 894 to 5710 ng g −1 in females. Seven PCB congeners (tetra-, penta- and hexachlorobiphenyls) accounted for 45% of total PCB (ΣPCB) in narwhal blubber. Narwhal had 1·4- to 8·6-fold higher ratios of tetra- and pentachlorobiphenyls to PCB-153 (2,2′,4,4′,5,5′-hexachlorobiphenyl), lower 4,4′-DDE/ΣDDT ratios and lower proportions of trans-nonachlor to total chlordane components than reported for odontocetes living in more contaminated environments. Mean ΣPCB concentrations in narwhal were 6- to 15-fold lower than in dolphins from the Canadian east coast and belugas from the St Lawrence River estuary, respectively, while PCC levels were from 4- to about 2-fold lower, and ΣHCH, dieldrin and ΣCBz differed by <2-fold. The pattern of organochlorines in narwhal tissues suggests they are exposed to proportionally more volatile compounds, and may have less capacity to metabolize some of these compounds, relative to odontocetes living nearer sources of these contaminants.