Hope Bay Research Articles

Diet of the Brown Skua (Stercorarius antarcticus lonnbergi) at Hope Bay, Antarctic Peninsula: differences between breeders and non-breeders

Fil: Borghello, Paloma. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Division Zoologia de Vertebrados. Seccion Ornitologia; Argentina

Sex-specific foraging strategies of Adélie penguins (Pygoscelis adeliae): Females forage further and on more krill than males in the Antarctic Peninsula

Sexual segregation characterises many animal communities, and in seabirds (including penguins), foraging strategies are known to vary with sex. The forging strategies of Adelie penguins (Pygoscelis adeliae) have been studied to some extent in some Antarctic locations; however, sex-based differences in foraging in this species have only been studied in depth in East Antarctica. Therefore, in this study, we aim to determine whether sexual segregation drives the foraging ecology [in terms of foraging habitat and diet based on analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes, respectively] of Adelie penguins in the Antarctic Peninsula (Hope Bay) during the breeding season. Our results showed strong sexual isotopic spatial segregation. Females forage for more krill than fish in more offshore, pelagic waters in contrast to males which feed equally on both items in more inshore, benthic waters. These results suggest a link between foraging habitat and diet that differs according to sex, similar to that found in East Antarctica. Given these similarities, we hypothesise that the foraging ecology of Adelie penguins varies with sex throughout the Antarctic continent. Nevertheless, further research in other locations such as in western Antarctica is needed to confirm this hypothesis.

Evidence of upgrading of gold tenor in an orogenic quartz-carbonate vein system by late magmatic-hydrothermal fluids at the Madrid Deposit, Hope Bay Greenstone Belt, Nunavut, Canada

Evidence of secondary gold enrichment due to the addition of new gold into an earlier orogenic quartz-carbonate vein deposit by magmatic-hydrothermal fluids is strongly suggested for the Madrid Deposit, hosted in the Hope Bay Greenstone Belt in Nunavut, Canada. The conclusion is based on an extensive in situ microanalytical protocol (SEM, confocal Raman microspectroscopy, microthermometry, decrepitate mound analysis, LA-ICP-MS, cathodoluminescence, SIMS) not previously applied to gold systems. This approach was used to characterize the mineralogy and fluid inclusion systematics associated with the upgrading event.Mineralization comprised of only Ag-bearing gold (“electrum”; 89.8 at. % Au avg.; n = 8) is present throughout all investigated laminated and brecciated orogenic quartz veins. However, in high-grade vein intersections where gold grades are locally elevated (up to 122 g/t), assemblages containing tennantite-tetrahedrite + chalcopyrite + electrum (80.7 at. % Au avg.; n = 15) ± AgPbAu tellurides occur that are texturally late-stage relative to electrum-only mineralization. Subdomains of quartz coeval with this later assemblage are optically- and texturally-distinct from earlier orogenic quartz. This late mineral assemblage is absent in all low-grade vein intersections (∼1 g/t Au avg.) examined where only electrum is identified. Quartz-hosted fluid inclusions (H2ONaCl ± CO2) of intermediate salinity (16.7 ± 1.2 wt.% NaCl equiv.; n = 93) were identified only in the high-grade vein samples and are present along healed planes associated with tennantite-tetrahedrite + chalcopyrite + electrum ± AgPbAu telluride assemblages. In situ SIMS δ18O analyses of quartz, combined with temperature constraints from mineral equilibria, show that early orogenic vein quartz and late quartz subdomains associated with gold upgrading precipitated from fluids with similar δ18OH2O values of 4.5–12.4‰ (n = 10) and −5.5 to 11.8‰ (n = 13), respectively. Isotopic data suggests that meteoric water was a negligible component in fluids responsible for gold precipitation. Microthermometry and Raman spectroscopy show that upgrading fluids were distinct in composition compared to the earlier metamorphic fluids (H2ONaClCO2 ± CH4 ± N2; 4.6 ± 1.6 wt.% NaCl equiv., n = 33) and later Canadian Shield basement brines (H2ONaCl; 22.4 ± 1.2 wt.% NaCl equiv., n = 12) which have also been identified in the fluid inclusion record at Madrid. Laser ablation ICP-MS analyses indicate the gold upgrading fluids are enriched in AsSbZnPb and LILE (CsBaRbSr); these data are consistent with late fluids derived from an evolved magmatic-hydrothermal system. Trace element mapping of pyrite, coupled with principle component analysis of the data, confirms a strong correlation between Au and AgTeSbBiW(As) in upgraded veins, whereas only Au and As strongly correlate in low-grade veins.The study suggests that gold upgrading, either involving newly introduced gold or remobilization of existing gold, can be linked to the incursion of a late magmatic-hydrothermal fluid that post-dated formation of the main orogenic-type auriferous quartz vein system. The geological setting and mineral-chemical features suggest an intrusion-related (i.e., porphyry), or intermediate-sulfidation epithermal mineralization style for the later event. This work provides another example of the importance of compositionally distinct cumulative hydrothermal events in the development of high-grade gold deposits in orogenic settings.

Age, Growth, and Sexual Maturity of the Channeled WhelkBusycotypus canaliculatus(Linnaeus, 1758) and Knobbed WhelkBusycon carica(Gmelin, 1791) in Narragansett Bay, Rhode Island

A total of 840 channeled (female, n = 388; male, n = 452) and 405 knobbed (female, n = 239; male, n = 166) whelks were measured for shell length (SL) and shell width (SW), with age estimates made from corresponding operculum annual growth striae readings. Gonads (ovary and testis) and reproductive structures [nidamental gland (females) and vas deferens (males)] were assessed macroscopically for maturity stage. All whelks used in this study were collected from Rhode Island state waters within Narragansett Bay, Mount Hope Bay, and Little Narragansett Bay (Pawcatuck River). Data were aggregated by species and sex, with each species treated as a single population within the study area. Age at size (growth rates) and age and size at 50% and 95% maturity were estimated for both species by sex. Female channeled whelk had the highest mean annual growth rates and reached minimum legal size quickest [minimum shell length (MSL) = 136.53 mm, minimum shell width (MSW) = 76.20 mm] and at the youngest age. Male channeled and female knobbed had similar growth rates and were the next quickest to reach MSL and MSW. Male knobbed grew slowest and were the last to enter the fishery and at the oldest age. Estimated age at 50% maturity (A50) for female channeled and female knobbed was nearly the same at 8.46 and 8.35 y, respectively. Male channeled had an estimated A50 of 7.35 y and that of male knobbed was 5.65 y. Estimated size at 50% maturity (SL50 and SW50) for female channeled was 136.8 mm SL and 77.5 mm SW; female knobbed was 124.0 mm SL and 68.4 mm SW; male channeled was 116.0 mm SL and 64.9 mm SW; and male knobbed was 89.4 mm SL and 47.7 mm SW. No instances of protandrous hermaphroditism, pseudohermaphroditism, or imposex were observed. A total of 231 newly hatched (age 0) knobbed whelks were measured for SL and SW, with mean SL and SW at age 0 included in age-at-size (growth rate) analyses.

Fish prey of Weddell seals, Leptonychotes weddellii, at Hope Bay, Antarctic Peninsula, during the late summer

The study of the feeding habits of Weddell seals, Leptonychotes weddellii, in the area of west Antarctic Peninsula is essential to understand the role they play in the marine food webs, especially considering that this is one of the regions most affected by climate change. With the aim of detecting temporal changes in the fish predation pattern of seals, a total of 217 scats were collected at Hope Bay, during three consecutive summers (2003, 2004 and 2005). The family Nototheniidae comprised over 80% in numbers of fish preyed by seals. The Antarctic silverfish, Pleuragramma antarctica, was, by far, the most frequent and abundant prey species with a mean percentage frequency of occurrence of 48.7% and representing in average 52.1% in numbers of the fish consumed by seals. Other fish species of lesser importance were the nototheniids Trematomus newnesi, Lepidonotothen larseni, Gobionotothen gibberifrons and the channichthyid Chionodraco rastrospinosus. Temporal variation was observed not only in the relative proportions of the different fish prey taxa but also in the sizes of the dominant prey, P. antarctica. Given the high trophic vulnerability of this species to changes in abiotic factors and food web structure and dynamics, a possible influence of El Nino Southern Oscillation events of 2002–2003 and 2004–2005 should not be discarded. Moreover, special attention should be addressed to its population status, distribution and spatial/temporal availability as prey resource of upper trophic level consumers such as L. weddellii which largely depend on P. antarctica.

Crustal shortening and thickening in Neoarchean granite-greenstone belts: A case study from the link between the ∼2.7 Ga Elu and Hope Bay belts, northeast Slave craton, Canada

The Elu Link between the ∼2.7 Ga Hope Bay and Elu belts in the northeast Bathurst Block of the Slave craton comprises supracrustal and intrusive rocks variably deformed by three tectono-metamorphic events (D1–D3). The geometry of D1 structures formed during prograde metamorphism is uncertain, because of subsequent overprint. D2 occurred in two stages predating (D2a) and postdating (D2b) peak metamorphism. D1 and D2a were thrusting events inferred from peak metamorphic pressures of ∼6.7 kbar (670 MPa) retained by a garnet orthogneiss. The latter is diagnostic of thrust tectonism in Archean granite-greenstone belts with no characteristic thrust faults. Unlike D2a, D2b was a vertical general flattening event prevailing during the formation of magmatic domes and interdomal folds that form the main strain patterns of the belts. This was followed by the formation of buckled F3 folds associated with D3 vertical constriction. The switch from thrust to vertical tectonics during peak metamorphism and subsequent deformation resulted in intense recrystallization that explains the poor preservation and scarcity of early-formed shears, including thrust zones. A tectonic process, combining D1+D2a thrust stacking, sagduction, and vertical stretching during D2b and D3, is suggested to explain crustal thickening in the Elu Link and terrains of similar ages.

Recent occupation by Adélie Penguins (Pygoscelis adeliae) at Hope Bay and Seymour Island and the ‘northern enigma’ in the Antarctic Peninsula

We excavated active and abandoned Adelie Penguin (Pygoscelis adeliae) colonies at Seymour Island and Hope Bay, Antarctic Peninsula, to determine an occupation history for this species at these sites. Previous research at Hope Bay has indicated an occupation there since the middle Holocene, based on a sediment record from Lake Boeckella. Excavations revealed only shallow and relatively fresh ornithogenic soils in the active colonies at the two localities. At least 53 abandoned pebble mounds were located at Hope Bay of which nine were excavated and four were sampled by probing to recover organic remains to determine their age. Radiocarbon dating of egg membrane, feather, and bone from both sites revealed a young occupation dating to less than ~600 years after correcting for the marine carbon reservoir effect. The mismatch in the geologic record of Adelie Penguin occupation in the northern Antarctic Peninsula, including Lake Boeckella sediments and geologic deposits and lake sediments on King George Island, with more direct evidence of breeding colonies from ornithogenic soils from active and abandoned colonies is hereby referred to as the ‘northern enigma’ as it does not occur in other regions of Antarctica including the southern Antarctic Peninsula, East Antarctica, or the Ross Sea, where the penguin record extends to the early to middle Holocene and matches well with the geologic record of deglaciation and penguin occupation. As yet, there is no convincing explanation for the ‘northern enigma’.

Laser Ablation ICP-MS U-Pb and 40Ar-39Ar age constraints on Neoarchean to Paleoproterozoic magmatic and tectono-metamorphic evolution of the link between Hope Bay and Elu greenstone belts, northeast Slave craton, NWT, Canada

The Elu Link connecting the Neoarchean Hope Bay and Elu granite-greenstone belts in the Bathurst block of the northeast Slave craton consists of volcano-sedimentary and gabbro–granite rocks. Laser ablation ICP-MS zircon and titanite U-Pb dating was combined with mineral 40Ar-39Ar age data to date the Elu Link rocks and D1–D3 tectono-metamorphic events, as well as characterize the response to the Thelon Orogeny in the area. The volcanic rocks are correlated with the ca. 2716Ma Flake Lake suite in the adjacent Hope Bay belt, whereas the sedimentary units have a minimum depositional age of 2684±11Ma nearly coinciding with the onset of D1 deformation. Most gabbro–granite bodies were emplaced between 2651±14Ma and 2577±13Ma coeval with the D2 deformation whose accompanying metamorphism culminated at 2632±7Ma. Older ages (up to 3042±22Ma) retained by either the gabbro–granite or their hosts are indicative of crustal contamination. A few gabbro–granites were also emplaced during the 2577±13Ma to 2494±21Ma D3 deformation event. However, the 2494±21Ma intrusions are unusual and mark the Archean–Paleoproterozoic transition. The D3 deformation was followed by erosional exhumation and localized thermal pulses associated with the emplacement of diabase dikes at 2228±8Ma, 2128±11Ma, and 802±75Ma. The Thelon Orogeny imprint, inferred from the 2054±11Ma to 1919±5Ma biotite ages, corresponds to nearly isobaric, low-temperature (<350°C) metamorphic re-equilibration.

Reproductive effort affects oxidative status and stress in an Antarctic penguin species: An experimental study

The oxidative cost of reproduction has been a matter of debate in recent years presumably because of the lack of proper experimental studies. Based on the hypothesis that different brood sizes produce differential reproductive costs, an experimental manipulation during breeding of Adélie penguins was conducted at Hope Bay, Antarctica, to study oxidative status and stress. We predict that a lower reproductive effort should be positively related to low oxidative and physiological stress. We randomly assigned nests with two chicks to a control reproductive effort group (CRE), and by removing one chick from some nests with two chicks, formed a second, low reproductive effort group (LRE). We examined how oxidative status in blood plasma (reactive oxygen metabolites, ROMs, and total antioxidant capacity, OXY) and stress (heterophil/lymphocyte ratio, H/L) responded to a lower production of offspring total biomass. Our nest manipulation showed significant differences in offspring total biomass, which was lower in the LRE group. As predicted, the LRE group had higher antioxidant capacity than individuals in the CRE group. We have also found, although marginally significant, interactions between sex and treatment in the three variables analysed. Females had higher OXY, lower ROMs and lower H/L ratio when rearing one chick, whereas males did so when rearing two except for OXY which was high regardless of treatment. Moreover, there was a significant negative correlation between the H/L ratio and OXY in females. Finally, we have found a negative and significant relationship between the duration of the experiment and OXY and ROMs and positive with H/L ratio which suggests that indeed breeding penguins are paying an effort in physiological terms in relation to the duration of the chick rearing. In conclusion, a reduction of the reproductive effort decreased oxidative stress in this long-lived bird meaning that a link exists between breeding effort and oxidative stress. However, our findings suggest different sex strategies which results in opposite physiological responses presumably depending on different life-history strategies in males and females.

Metamorphism in Neoarchean Granite-Greenstone Belts: Insights from the Link between Elu and Hope Bay Belts (∼2.7 Ga), Northeastern Slave Craton

AbstractThe Elu Link in the northeast Bathurst Block of the Slave Craton, Canada, is composed of variably D1–D3-deformed, low- to medium-grade supracrustal and intrusive rocks connecting the Neoarchean Hope Bay and Elu granite-greenstone belts (∼2.7 Ga). Textural observations and pseudosection modeling show that the primary metamorphic reactions in the supracrustal rocks derived from D1-assisted hydrothermal alteration in albite-epidote hornfels-facies to greenschist-facies conditions. This was followed by one main cycle of prograde, peak, and retrograde metamorphism that variably accompanied D1 and D2 events along a clockwise pressure-temperature (PT) path. The pseudosection for a garnet-bearing orthogneiss whose protolith emplacement occurred before peak metamorphism indicates maximum upper-amphibolite conditions of 6.7 kbar and 710°C, reached during D2 deformation. Thereafter, the orthogneiss followed a counterclockwise PT path showing an increase in pressure (up to 8.7 kbar) during the late stages of ...

Penguin activity modify the thermal regime of active layer in Antarctica: A case study from Hope Bay

Monitoring permafrost and active layer is essential for prognostic research of future climate scenarios. Although biotic factors have a prominent role in active layer behavior, apart from vegetation effects, their influence remains little investigated. It is generally assumed that frozen ground exerts influence on nesting fauna, whereas, on the other hand, land colonization by birds, such as penguins can also interfere with the soil thermal regime. However, to our knowledge, no studies report on permafrost and active layer regime changes under penguin activity. We present a comparative study of two adjacent sites located in Hope Bay, one representing an active penguin rookery-S1, and another, an adjacent abandoned site currently vegetated-S2. Soil temperature and water content, and air temperature were monitored hourly from 2009 to 2011. Current penguin activity and the resulting deposition of guano during spring and summer in S1 is an important factor for explaining the higher number of thaw degree days due to direct physical impact and chemical reactions caused by rapid guano decomposition. In the vegetated S2 site, the snow pack lasted longer, showing the highest mean minimum temperature and larger thermal insulation, as well as larger FDD than those found in the bare soil of the active rookery (S1), and lower n-F, due to greater thermal insulation. Penguins played a significant role in changing the active layer depth and thermal regime, and represent a neglected actor on the ground thermal regime in Antarctic terrestrial environments.

Gastrointestinal helminths of Adélie penguins (Pygoscelis adeliae) from Antarctica

Knowledge about parasitic organisms in Antarctica is scarce and fragmentary. The study reported here adds to the knowledge of gastrointestinal parasites of the Adelie penguin ( Pygoscelis adeliae ) (Sphenisciformes), from 25 de Mayo/King George Island (South Shetlands), Bahia Esperanza (Hope Bay) and Avian Island (Antarctica). Thirty-five freshly dead specimens (20 chicks and 15 adults) were collected from December 2007 to December 2014 and examined for internal macroparasites. Three adult parasite species were found: one Cestoda, Parorchites zederi , and two Nematoda, Stegophorus macronectes and Tetrameres sp. Immature Tetrabothrius sp. were found in hosts from Avian Island. Helminth communities are known to be related to host feeding behaviours. Low parasite richness observed in Adelie penguins could be related to the stenophagic and pelagic diet of this host species, which feeds almost exclusively on krill. Keywords: Parorchites zederi ; Stegophorus macronectes ; Tetrameres sp.; parasites; ecosystem health. (Published: 16 June 2016) Citation: Polar Research 2016, 35 , 28516,http://dx.doi.org/10.3402/polar.v35.28516

The cephalopod prey of the Weddell seal, Leptonychotes weddellii, a biological sampler of the Antarctic marine ecosystem

Weddell seals, Leptonychotes weddellii, are important apex predators in the food web of the Antarctic marine ecosystem. However, detailed information on their trophic relationships with cephalopods is scarce. Moreover, cephalopods play a key role in the marine environment, but knowledge of their feeding habits is limited by lack of data. Here, we have combined the use of this seal as a biological sampler together with measurements of the stable isotopic signature of the beaks of their cephalopod prey. Thus, the aims of the present study were: (1) to examine in detail the cephalopod portion of the diet of Weddell seals by means of scat analysis and (2) to assess the habitat use and trophic level of the different cephalopod prey taxa identified. From January to February 2009, a total of 48 faecal droppings were collected at Hope Bay, Antarctic Peninsula. Cephalopods were mainly represented by beaks (n = 83) which were identified to the lowest possible taxonomic level. Furthermore, subsamples of beaks were separated for further isotopic analysis. Relative abundance of stable isotopes of carbon (δ13C) and nitrogen (δ15N) was determined by continuous-flow isotope-ratio mass spectrometry. Cephalopods were represented uniquely by octopods of the subfamily Eledoninae. Pareledone turqueti was the dominant prey species followed by the papillated Pareledone species group and Adelieledone polymorpha. We conclude that Weddell seals preyed primarily on benthic prey resources. Furthermore, the relatively similar δ13C and δ15N values in beaks of the three octopod prey taxa suggest that these share the same type of habitat and occupy similar trophic level positions.

Comparative study of moss diversity in South Shetland Islands and in the Antarctic Peninsula

This paper presents a comparative study of moss diversity in three collection sites in the South Shetland Islands (King George, Elephant, and Nelson Islands) and one in the Antarctic Continent (Hope Bay, Antarctic Peninsula). In the King George, Elephant, and Nelson Islands, the collections were done in ice-free areas during the austral summers of years 1988, 1989, 1990, 1991, 1992, and 1994. In Hope Bay, the collections were done in the 2009 summer (February). All collections were deposited in the HCB (Chaves Batista Herbarium). The King George Area is the most diverse area and the Hope Bay has the lowest diversity stats. The diversity stats for each region and the similarities between both are presented. This results suggested that harder climatic conditions determine lower diversity for the bryoflora.

Soils and Landforms at Hope Bay, Antarctic Peninsula: Formation, Classification, Distribution, and Relationships

Antarctic soils occur in restricted areas, but few integrated studies on soils and landforms have focused in the Antarctic Peninsula. We studied the representative soils of Hope Bay, emphasizing the processes of quaternary sedimentation, landforms, soil classification, and distribution. Results show that landforms and soils are closely associated in Hope Bay. Ornithogenic soils are associated with Late Pleistocene to Holocene stable ground moraines; these are currently being destroyed by thermokarst erosion around Lake Boekella. Lithic Haploturbels occur chiefly on shallow rocky terrains whereas Typic Haploturbels are found on patterned ground. In Hope Bay, a much colder climate prevails compared with the South Shetlands, and the widespread permafrost close to the surface warrants strong cryoclastic weathering with active and general gelifraction across different lithologies. The shallow occurrence of permafrost in Hope Bay has a strong regulating effect on soils, retarding leaching and soil development processes. Local soils are, in general, shallow and cryoturbic, and the current pedoenvironment on lowland stable areas was subjected to varying phosphatization on previously weathered sedimentary material. The evidence of phosphatization of a formerly larger area appears to be the main driver of pedogenesis at Hope Bay, and nesting activity by penguins on stable surfaces is capable of enhancing weathering and soil formation.

Dimethylsulfide metabolism in marine isolates and their role in the biogeochemical cycling of sulfur (575.8)

Microbial degradation is a major sink for dimethylsulfide (DMS), a volatile organosulfur compound which has been implicated in climate control and the biogeochemical cycling of sulfur. While the majority of marine bacteria which are capable of growth on DMS are members of the Methylophaga genus and belong to the Gammaproteobacteria class, recent studies have demonstrated that bacteria belonging to the Alphaproteobacteria class are also able to metabolize DMS. For example, a DMS monooxygenase, which carries out the first step in the DMS degradation pathway, was recently isolated from Hyphomicrobium sulfonivorans, the first enzyme of its kind to be isolated and characterized.1 The enzyme is a member of the flavin‐linked monooxygenases of the luciferase family and is most closely related to nitrilotriacetate monooxygenases. This work reports on the DMS monooxygenase activity of several bacteria isolated from Mount Hope Bay, RI.Grant Funding Source: NSF

Genesis, mineralogy and ecological significance of ornithogenic soils from a semi-desert polar landscape at Hope Bay, Antarctic Peninsula

Large amounts of organic matter of marine origin are seasonally deposited on ice-free soils by birds and mammals, especially penguins, in some restricted Antarctic terrestrial ecosystems. The incorporation of this material into the mineral soil matrix becomes the main pathway for the widespread formation of phosphate minerals and ornithogenic soils, enhancing local biodiversity and complexity. These soils have been well-studied in Maritime Antarctica, and comparatively neglected in the cold, dry polar Antarctica. Hence, we studied the influence of penguins on soil and landscape formation at Hope Bay, a transition climatic zone in Antarctic Peninsula, where no previous pedological study has been undertaken with regards to soil phosphatization. Ten pedons, nine of which are ornithogenic, were described, sampled, and analyzed for physical, chemical and mineralogical properties. Results indicate that the slow mineralization of bird guano, coupled with high levels of organic matter and reduced leaching, notably Ca, contribute to reduced soil acidification and low exchangeable Al3+ content, unlike ornithogenic soils from Maritime Antarctica. Phosphate minerals typical of the phosphatization process, such as taranakite, minyulite, leucophosphite, struvite, and fluorapatite, were detected. In Hope Bay, they are subjected to very slow rates of dissolution, neoformation of secondary phosphatic minerals, and mineralogical transformation and leaching processes. Ornithogenesis is viewed as a mechanism of sea-land nutrient transfer, enriching the latter, since the parent rocks are chemically poor sedimentary materials. On the other hand, the presence of kaolinite indicates wetter climate conditions in the past, with periods with greater moisture and weathering, compared with the current semi-polar desert environment. We conclude that the phosphatization process overprints previously weathered sedimentary materials.

Postglacial lake shoreline surveys and lacustrine paleobiotic records in northern Bruce and Grey counties, Ontario, Canada

Northern Grey and Bruce counties are situated centrally in the Lake Huron basin of the Great Lakes area of North America and are similarly central to the area of glacial Lake Algonquin, the largest glacial lake of the Great Lakes area. Ten survey traverses at sites in northern Grey and Bruce counties have documented the continuation of Lake Algonquin and Nipissing phase shorelines onto the Bruce Peninsula from previous work to the east. The Algonquin shoreline near 240m ASL (above sea level) rises northward above land high enough to record it near Lion's Head. The Nipissing shoreline at 191m ASL defines a shallow strait across the Bruce Peninsula near Ferndale, which was flooded temporarily at the maximum of the Nipissing transgression, separating northern Bruce Peninsula from the mainland. Uplift and Port Huron outlet downcutting later rejoined the island to the mainland as it is today. Raised beaches define Algonquin and Nipissing regressions by uplift using the Port Huron outlet. Paleobiotic records in a sand dune at Oliphant (molluscs), a Nipissing shorebluff along Sucker Creek (molluscs) and several sites in the former Nipissing shallow water strait near Ferndale (molluscs, ostracodes, plant macrofossils), provide paleoenvironmental data and supplement prior pollen studies at Lake Charles, Slough of Despond, and Hope Bay. Lake Algonquin deep water rhythmite clays are barren of fossils, whereas Nipissing shallow water silts are fossiliferous.

Micromorphological and microchemical indicators of pedogenesis in Ornithogenic Cryosols (Gelisols) of Hope Bay, Antarctic Peninsula

Micromorphological investigations of Antarctic soils are comparatively scarce, however, they could help understand the genesis of cryogenic soils under extreme polar conditions and different biotic factors. In most areas of Maritime Antarctica, the soil structure is apparently influenced by the local lithology, cryoturbation, guano deposition and reaction of guano solutions. The present study was carried out in Hope Bay, in the northern part of the Antarctic Peninsula, possibly one of the oldest sites of penguin occupation in the region. We describe and analyze the most important micro and sub-microscopic features of selected Ornithogenic Cryosols (Gelisols) from this part of Antarctic Peninsula, representing a transitional climatic zone between the wetter South Shetlands and the much drier Weddell Sea sector. Nine pedons representing the main ornithogenic soils found in ice-free areas of Hope Bay were selected for the micromorphological study. Undisturbed soil blocks were sampled at different depths, ranging between 0 and 30cm. The microstructure and sub-microstructure were further investigated using a JEOL 8200 and a Zeiss scanning electron microscopes, both coupled with an microprobe (SEM/WDS). These pedons have a very limited surface accumulation of organic matter formed by mosses and lichens, changing abruptly to a mineral phosphatic horizon of bleached colours, and usually hardcemented by ice. A small to medium-sized granular structure is generally observed, with ovoidal, subrounded forms, including several well-defined ornithogenic materials, such as P-rich organic remains, nodular phosphates forms and minute fragments of bone apatite. The chemical composition of ornithogenic materials and phosphatic coatings indicates the presence of discrete forms of taranakite, minyulite, leucophosphite, struvite and fluorapatite, typical of phosphatization process in these soils. Phosphatization and enhanced chemical alteration of the substrate and is one of the main soil-forming process in ornithogenic soils, resulting in P-rich ovoidal aggregates formation. P-rich solutions penetrate desiccation fractures and cleavage planes in large clasts and react preferably with plagioclases. P reacts with Al and Fe to form various amorphous and crystalline P phases. Present day permafrost cementation of deeper phosphate layers indicate that warmer/wetter conditions occurred in the past, during which P was leached downwards and reacted with the rock substrates, developing stable ovoidal aggregates, now incorporated in ice-cemented subsurface horizon.

Stratigraphy and geochemistry of the igneous rocks in the Elu Link between Hope Bay and Elu greenstone belts, northeast Slave craton: tectonic setting and implications for gold mineralization

Geological investigation of the rocks in the Elu Link has provided new information on the geodynamic origin of the Neoarchean (ca. 2716–2663 Ma) Hope Bay and Elu granite–greenstone belts. Stratigraphic and geochemical features of these rocks and those of the nearby Flake Lake area in the Hope Bay belt suggest that the two greenstone belts are contiguous, having similar mafic-dominated bimodal rocks comprising abundant basalts to andesites and less common dacites and rhyolites hosting gabbroic and trondhjemite–tonalite–granodiorite (TTG) intrusions. The corresponding parental magmas, whose evolution likely occurred via fractional crystallization and juvenile crustal contamination, formed from both deep and shallow mantle sources. The basalts, andesites, gabbros, and felsic volcanic rocks are variably tholeiitic to calc-alkaline. Chondrite- and primitive mantle-normalized profiles demonstrate (1) flat to slightly fractionated heavy rare-earth element (HREE) patterns with a weak negative Eu anomaly and (2) light rare-earth element (LREE) enriched and strongly fractionated HREE patterns with variable negative to positive Eu anomalies. In contrast, TTG rocks are calc-alkaline, with strong LREE enrichment, HREE depletion, and variable positive Eu anomalies. Altogether, the rocks exhibit Nb and Ti troughs, and variable Nb/Ta, La/Ta, and Zr/Hf ratios indicative of crustal contamination. Chalcophile elements and related ore deposits in the area are inferred to be formed from hydrothermal fluids mobilized during emplacement and after crystallization of their host rocks. An extensional, high-heat-flow back-arc tectonic environment is proposed to explain the stratigraphic and geochemical characteristics and the presence of large gold resources in these greenstone belts.