2017

Permanent URI for this collectionhttps://hdl.handle.net/1807/75484

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Magnetization Age from Paleomagnetism of the Copper Harbor Red Beds, Northern Michigan, USA, and its Keweenawan Geologic Consequences.
(Canadian Science Publishing, 2017-10-05) Symons, Dave T.A.; Kawasaki, Kazuo; Diehl, J.
The Copper Harbor Formation on Lake Superior’s Keweenaw Peninsula records the transition from volcanic to sedimentary infilling of North America’s 1.1 Ga Keweenawan rift. Radiometric dating shows that the formation’s primary mafic sediments and interbedded “Lake Shore” flows were deposited between ∼1092 and ∼1082 Ma. Our regional paleomagnetic results for the Copper Harbor’s red beds yield a dominantly prefolding normal-polarity secondary chemical characteristic remanent magnetization in hematite at 18 of 21 sites with a mean direction of declination = 274.9°, inclination = +10.9° (k = 69.5, α95 = 4.2°), and a paleopole at 7.4°N, 181.7°E (A95 = 3.3°). Using paleopoles from Keweenawan volcanic rocks with U–Pb zircon age dates, an apparent polar wander path is constructed from 1106 ± 2 Ma to 1087 ± 2 Ma. Extrapolation of this path dates oxidation of the Copper Harbor’s primary gray beds to red beds at 1060 ± 5 Ma. The path implies an apparent polar wander rate of ∼18 cm per year from ∼1108 Ma to 1096 Ma and of 6.8 cm per year from 1096 Ma to 1087 Ma, along with a consistent clockwise rotation of 0.30 ± 0.05°per million years for the Laurentian Shield from ∼1108 to ∼1160 Ma. Further, most Keweenawan volcanic rocks around the Lake Superior region carry an endemic ∼1060 Ma normal-polarity hematite remanence overprint, acquired during the initial stages of Grenvillian tectonic uplift, that has caused asymmetry in a unit’s normal and reverse paleopoles. Also, the Copper Harbor paleopole dates emplacement of the White Pine stratiform sedimentary copper mineralization more precisely at 1060 ± 5 Ma.
In situ geochemical characterization of pyrite crystals in burial dolomites of St. George Group carbonates
(Canadian Science Publishing, 2017-11-02) Olanipekun, Babatunde John; Azmy, Karem
SIMS was used to measure the δ34S of pyrite disseminated in burial dolomite matrix of St. George Group at three localities in western Newfoundland. At Main Brook, δ34S values for the pyrite grains show wide variation (-15 to +20 ‰ (n = 20), but are mostly negative. Combined with a paucity of two-phase fluid inclusions in the host burial dolomite, the depleted δ34S values suggest that the pyrite is a by-product of BSR. Predominantly negative δ34S values was also obtained for sampled pyrite at Daniel’s Harbour and Port au Choix, however relatively high homogenization temperatures (>100oC) of two-phase fluid inclusions in the host dolomites is incompatible with a BSR process for pyrite formation. More so, Daniel’s Harbour is a site for main stage sulfide mineralization (MVT system), hosted in similarly burial dolomite and that has been previously constrained to be associated with TSR. A relative proximity of the currently studied pyrite samples to this MVT system deposit is thus inconsistent with an in-situ BSR for these pyrites. The analyzed pyrite grains are encased in bitumen, post-date burial dolomite and pre-date late stage saddle dolomite. Thus, the depleted δ34S signature was likely inherited from migrated hydrocarbons in the reservoir. Incursion of an initial pulse of hot sulfate-rich brine into the formation can cause thermal cracking of hydrocarbons, thereby releasing its low δ34S. Subsequently, the main stage sulfide mineralization (Mississippi Valley Type deposit) occurred via in-situ TSR. These findings have implication for the paragenetic history of sulfide minerals precipitated during MVT-type mineralization.
Tectonostratigraphic and petrogenetic setting of late Mississippian volcanism in eastern Canada
(Canadian Science Publishing, 2017-12-06) Jutras, Pierre; Dostal, Jaroslav; Kamo, Sandra; Matheson, Zachary
In the aftermath of the Middle Devonian Acadian Orogeny, a thick mafic body is inferred to have been emplaced at the base of the crust during development of the Maritimes Basin complex in eastern Canada and is believed to have sourced regional Late Devonian to Mississippian volcanism. By late Mississippian times, volcanism was limited to central New Brunswick and the Magdalen Islands of eastern Quebec. Whereas Late Devonian to early Mississippian mafic volcanism was mainly characterized by subalkaline lavas produced by the high-degree partial melting of a subduction-enriched lithospheric mantle source, late Mississippian volcanism was dominated by alkali mafic lavas produced by the low-degree partial melting of a sublithospheric mantle source that shows no evidence of subduction imprint. Two distinct upper Mississippian volcanic successions were identified in central New Brunswick and are estimated to be separated by ∼7 million years based on U–Pb dates on felsic intervals. They respectively belong to the Cumberland Hill Formation and a new volcanic member of the Hopewell Cape Formation. As they share close geochemical affinities, we interpret both volcanic units as having been derived from the same primary source but from distinct magmatic pulses. Based on the sedimentology of interbedded clastic units as well as available mapping and geophysical data in New Brunswick, we interpret that the upper Mississippian mafic lavas were issued from large NW–SE striking dykes responding to NW–SE compression in a pull-apart basin, whereas less voluminous and more localised felsic rocks were possibly issued from discrete volcanic pipes.
Understanding fluid behavior through ion and isotope data from the Yitong Basin, Northeast China
(Canadian Science Publishing, 2017-12-22) Zhao, Rongsheng; Shan, Xuanlong; Yi, Jian; Liang, Ye; Li, Chunlong; Qiu, Cuiying
To evaluate ion origins and fluid behavior, the chemical properties of thermal water sampled from the Eocene reservoir in the Yitong Basin (YB), Northeast China, were investigated. The thermal water samples are classified as Na–HCO3-type water and were fully equilibrated, except for Sijixiangkang (SJXK) and Yitong (YT). The cations originate mainly from water–rock interactions (e.g., albitization and weathering of plagioclase), while the anions originate from magmatic volatiles and leaching of limestone and granite, which were heated by hot magmatic volatiles and exhibited an evaporation-like pattern in the Gibbs diagrams. The existence of magmatic volatiles was verified by the high ion ratio, the minor-element origins, δ13C values of HCO3, and δ34S values of SO4, which flowed upward along lithospheric faults, with higher fluxes in the northeast than in the southwest (the δ13C value of the Chaluhe depression (CD) is 0.93‰ lower than that of the Moliqing depression (MD, 1.63‰)). Furthermore, according to the Br/Cl and HCO3−/Cl ratios and the δ13C values, we speculate that a deep Permian limestone reservoir exists below the granitic unit. Based on the ion origins and fluid potentials, we conclude that the CD and MD are open systems rather than closed systems. The recharged water migrates from the margin to the center in the plane, and in the vertical direction, it migrates from the Yongji (E2y) and Sheling (E2sh) strata to the overlying strata and underlying Shuangyang (E2s) strata along faults. By summarizing all of the available data, we proposed a conceptual model of fluid migration.
Late Cretaceous radiolarians from a bentonitic-rich interval at the base of the Niobrara Formation, southwestern Saskatchewan, Canada: biostratigraphic and paleoenvironmental implications
(Canadian Science Publishing, 2017-11-03) Diaz, Juan F.; Velez, Maria I.
A radiolarian assemblage containing 11 species of both nasellarians and spumellarians was recovered from the Upper Cretaceous Niobrara Formation in southwestern Saskatchewan, Canada. This assemblage represents the first report of Coniacian radiolarians in the entire Western Interior Basin and one of the few reports for the Upper Cretaceous in North America. The presence of radiolarians and the partial disappearance of foraminifera in the only bentonitic interval in this formation suggest that high silica concentrations supplied by volcanic events favored ecological conditions for radiolarians to thrive and or enhanced their preservation before and after deposition. Correlation of this assemblage with other Upper Cretaceous radiolarian assemblages in North America shows a close affinity with the microfauna recovered in the Sverdrup Basin (Canadian Arctic).
Real-time monitoring for structural health, public safety, and risk management of mine tailings dams
(Canadian Science Publishing, 2017-11-26) Hui, Shiqiang (Rob); Charlebois, Lawrence; Sun, Colin
Public awareness of tailings dam failures is increasing in the wake of incidents in Canada and abroad. The present work establishes the current state of practice in mine tailings dam monitoring and provides a summary of the current technical and operational gaps identified through industry and stakeholder engagement. These gaps may be addressed with currently available technologies supplied by commercial instrumentation manufacturers; however, the assumed costs and lack of regulatory demand may serve as barriers to adoption. An integrated approach and diverse suite of technologies is needed to address issues of dam stability, worker and public safety, and environmental protection. Technological applications and limitations are described and design requirements are proposed for an integrated, real-time monitoring system. Socio-economic impacts and loss reduction benefits are considered and the need for industry and regulator participation is emphasized.
Geoelectric structure of the Great Slave Lake shear zone in northwest Alberta: implications for structure and tectonic history
(Canadian Science Publishing, 2017-10-05) Wang, Enci; Unsworth, Martyn J.; Chacko, Thomas
The study of ancient plate boundaries can provide insights into the past and present-day tectonic processes. Here, we describe a magnetotelluric (MT) study of the Precambrian basement of the Hay River Fault (HRF) in northwest Alberta, which is the southwest segment of the Great Slave Lake shear zone. New broadband MT data were collected to give a clearer image of the crustal structure. The Western Canada Sedimentary Basin was imaged as a low resistivity layer above the resistive crystalline basement. Four basement conductors were defined, and correlate with the terrane boundaries delineated with aeromagnetic data. These are (1) a major conductor in the Kiskatinaw domain, (2) a conductor on the boundary of the Ksituan and Chinchaga domains, (3) a conductor on the boundary of the Chinchaga and Buffalo Head domains and (4) a conductor near the Hay River Fault. Both (1) and (2) correspond to areas of high seismic reflectivity. The low resistivity can be explained by interconnected grain boundary graphite or sulfide phases deposited by metamorphic fluid migration. The HRF was not definitively located in previous studies. The new data show that the HRF could be thin (1 km) or wide (10 km) and located at the boundary of the contrasting aeromagnetic anomalies or further to the north. Various tectonic processes are proposed to interpret the possible locations of the HRF. No electrical anisotropy structure is required to interpret the MT data in this study.
Underwater faunal assemblages: radiocarbon dates and late Quaternary vertebrates from Cold Lake, Alberta and Saskatchewan, Canada
(Canadian Science Publishing, 2017-11-26) Jass, Christopher N.; Caldwell, Devyn; Barron-Ortiz, Christina Isabelle; Beaudoin, Alwynne B.; Brink, Jack; Sawchuk, Matthew
Late Quaternary faunal remains from three underwater settings in Cold Lake, Alberta and Saskatchewan, Canada, include at least 13 vertebrate taxa consistent with assemblages that post-date the Last Glacial Maximum (LGM). Seven new radiocarbon dates range from 10350Âą40 yr BP to 161Âą23 yr BP and provide insight into the post-LGM biotic history of east-central Alberta and west-central Saskatchewan. The presence of an essentially modern large mammal biota is suggested for the mid-Holocene, and possibly earlier, if the absence of extinct or extirpated taxa in association with Late Pleistocene Bison at the AB-SK site is meaningful. Taphonomically, some of the remains suggest deposition in open environments during the Holocene, possibly when lake levels were lower. The recovery of late Quaternary faunal remains from a present-day lacustrine setting is novel, and suggests that similar records may occur in other lakes in western Canada, including those in areas with scarce Quaternary vertebrate records.
Mineralogy and genesis of the Ni–Co lateritic regolith deposit of the Çaldağ area (Manisa, western Anatolia), Turkey
(Canadian Science Publishing, 2017-11-14) Helvacı, Cahit; Oyman, Tolga; Gündoğan, İbrahim; Sözbilir , Hasan; Parlak , Osman; Kadir, Selahattin; Güven, Necip
The Çaldağ Ni–Co deposit is characterized by a reddish brown oxide lateritic regolith, containing residual Ni deposit formed by the intense tropical weathering of peridotites. Nickel–Co ore is associated with transported ferricrete during the late Paleocene – middle Eocene, represented by colloform Fe oxides and residual lateritization during the Oligocene. The lateritic regoliths are developed over dunitic ultramafic rocks and consist mainly of smectite, berthierine, kaolinite, gypsum, pyrite, takovite, and pecoraite. These units were examined using polarized-light microscopy, X-ray diffraction, scanning and transmission electron microscopy, and geochemical methods. Mineralogical zonation from the base of the profile upwards has the following zones: ultramafic bedrocks, serpentinized ultramafic rocks (saprock), saprolite, carbonate- and sulfide-bearing zone, ferruginous saprolite zone, and silcrete. In addition, Fe oxides, smectite and opal-CT, and quartz increase towards the surface, whereas olivine, pyroxene, and serpentine decrease upwards in response to chemical weathering. Nickel–Co mineralization associated with Fe oxides and smectitic clays formed under wet and dry conditions, respectively, as a result of an increased Fe2O3 + Al2O3 + Ni + Co/MgO ratio. Field observations and mineralogical and geochemical analyses reveal that the smectite formed under basic conditions was controlled by multistage chemical weathering of ultramafic and volcanic rocks and by the concentrations of Si, Al, Fe, and Mg. Locally, concentrations of S in conjunction with Fe and Ca resulted in precipitation of goethite–hematite, gypsum, and pyrite in dissolution voids in association with smectite under acidic conditions that developed in a well-drained system.
Dinosaur eggshells from the lower Maastrichtian St. Mary River Formation of southern Alberta, Canada
(Canadian Science Publishing, 2017-11-14) Voris, Jared T; Zelenitsky, Darla K.; Therrien, François; Tanaka, Kohei
North America is known for its rich uppermost Cretaceous record of dinosaur egg remains, although a notable fossil gap exists during the lower Maastrichtian. Here we describe a diverse dinosaur eggshell assemblage from the St. Mary River Formation of southern Alberta that, in conjunction with recently described eggs from the same formation in Montana, helps fill this gap and sheds light on the dinosaur diversity in this poorly fossiliferous formation. Three theropod eggshell types (Continuoolithus cf. C. canadensis, Montanoolithus cf. M. strongorum, and Prismatoolithus cf. P. levis) and one ornithopod (Spheroolithus cf. S. albertensis), are reported from Albertan exposures of the St. Mary River Formation, increasing the ootaxonomic diversity of the formation from two to five ootaxa. The taxonomic composition of the eggshell assemblage is consistent with the dinosaurian fauna known from the St. Mary River Formation based on skeletal remains. Spheroolithus eggshells constitute the majority of identifiable eggshells in our assemblage, a trend also observed in several other Upper Cretaceous formations from North America. Continuoolithus is shown to be synonymous with Spongioolithus, thus expanding the Maastrichtian geographic range of the ootaxon to include Utah. The St. Mary River eggshell assemblage supports a general trend of increase in eggshell thickness among theropod ootaxa from the uppermost Santonian through the Maastrichtian, which is inferred to reflect an increase in body size among some clades of small theropods through the Upper Cretaceous. Eggshell preservation in the St. Mary River Formation may be related to the semiarid climatic and environmental conditions that prevailed.
Dinosaur eggshells from the lower Maastrichtian St. Mary River Formation of southern Alberta, Canada
(Canadian Science Publishing, 2017-11-14) Voris, Jared T; Zelenitsky, Darla K.; Tanaka, Kohei; Therrien, François
North America is known for its rich uppermost Cretaceous record of dinosaur egg remains, although a notable fossil gap exists during the lower Maastrichtian. Here we describe a diverse dinosaur eggshell assemblage from the St. Mary River Formation of southern Alberta that, in conjunction with recently described eggs from the same formation in Montana, helps fill this gap and sheds light on the dinosaur diversity in this poorly-fossiliferous formation. Three theropod types (Continuoolithus cf. C. canadensis, Montanoolithus cf. M. strongorum, and Prismatoolithus cf. P. levis) and one ornithopod (Spheroolithus cf. S. albertensis), are reported from Albertan exposures of the St. Mary River Formation, increasing the ootaxonomic diversity of the formation from two to five ootaxa. The taxonomic composition of the eggshell assemblage is consistent with the dinosaurian fauna known from the St. Mary River Formation based on skeletal remains. Spheroolithus eggshells constitute the majority of identifiable eggshells in our assemblage, a trend also observed in several other Upper Cretaceous formations from North America. Continuoolithus, is shown to be synonymous with Spongioolithus, thus expanding the Maastrichtian geographic range of the ootaxon to include Utah. The St. Mary River eggshell assemblage supports a general trend of increase in eggshell thickness among theropod ootaxa from the uppermost Santonian through the Maastrichtian, which is inferred to reflect an increase in body size among some clades of small theropods through the Upper Cretaceous. Eggshell preservation in the St. Mary River Formation may be related to the semi-arid climatic and environmental conditions that prevailed.
Three-dimensional hydrostratigraphy of the Orangeville Moraine area, Southwestern Ontario, Canada
(Canadian Science Publishing, 2017-11-26) Burt, Abigail K.
Regional-scale three-dimensional modelling of Quaternary sediments in the Orangeville Moraine area of southwestern Ontario has been completed as part of the Ontario Geological Survey groundwater initiative and provides an improved understanding of the glacial history and conceptual hydrostratigraphic framework for that region. Older (Marine Isotope Stage (MIS) 3-5) diamicton, glaciolacustrine, glaciofluvial and rare non-glacial deposits forming regional aquitards and local aquifers are found in the northwestern part of the area. Catfish Creek Till, deposited during the late glacial maximum (LGM) (MIS 2), forms a key aquitard and stratigraphic marker at depth. Diamicton, fine-textured glaciolacustrine sediments, and the gravel, sand and silt conduit and subaqueous fan sediments that comprise the overlying Orangeville Moraine were deposited in an ice walled lake formed between ice lobes during retreat from the LGM. Diamicton deposited during late glacial ice margin fluctuations forms the upper aquitard unit and buries the edges of the moraine. The Orangeville Moraine is the largest aquifer in the area, and is partially confined by the upper tills. Thick fine-textured glaciolacustrine deposits, Catfish Creek Till and older aquitards separate the moraine from bedrock aquifers across most of the area. Depending on hydraulic gradients, buried bedrock valleys with gravel and sand fills have the potential to recharge the bedrock aquifer.
Using a Multiple Variogram Approach to Improve the Accuracy of Subsurface Geological Models
(Canadian Science Publishing, 2017-07-29) MacCormack, Kelsey; Arnaud, Emmanuelle; Parker, Beth L.
Subsurface geological models are often used to visualize and analyze the nature, geometry, and variability of geologic and hydrogeologic units in the context of groundwater resource studies. The development of three-dimensional (3D) subsurface geological models covering increasingly larger model domains has steadily increased in recent years, in step with the rapid development of computing technology and software and the increasing need to understand and manage groundwater resources at the regional scale. These models are then used by decision makers to guide activities and policies related to source water protection, well field development, and industrial or agricultural water use. It is important to ensure that the modelling techniques and procedures are able to accurately delineate and characterize the heterogeneity of the various geological environments included within the regional model domain. The purpose of this study is to examine if 3D stratigraphic models covering complex Quaternary deposits can be improved by splitting the regional model into multiple sub-models based on the degree of variability observed between surrounding data points and informed by expert geological knowledge of the geological/depositional framework. This is demonstrated using subsurface data from the Paris Moraine area near Guelph in southern Ontario. The variogram models produced for each sub-model region were able to better characterize the data variability resulting in a more geologically realistic interpolation of the entire model domain as demonstrated by the comparison of the model output with pre-existing maps of surficial geology and bedrock topography as well as depositional models for these complex glacial environments. Importantly, comparison between model outputs show significant differences in the resulting subsurface stratigraphy, complexity and variability, which would in turn impact groundwater flow model predictions.
Tectonic and chemical implications of cathodoluminescent microstructures in quartz, Parry Sound domain, Ontario, Canada
(Canadian Science Publishing, 2017-03-01) Mills, Stephanie Gayle; Gerbi, Christopher; Marsh, Jeffrey H.; Yates, Martin G.; Seaman, Sheila J.; White, Joseph C.
Cathodoluminescence (CL) imaging of quartz in orthogneiss of the Parry Sound domain, Grenville Province, Ontario, Canada reveals four dark microstructures - medium-dark grains, mantles, sinuous lines, and straight lines. The Parry Sound domain experienced granulite-facies deformation and metamorphism followed by variable degrees of amphibolite-facies retrogression associated with the development of retrograde shear zones. We integrate our observations of CL-visible quartz microstructures with structures observable with optical and scanning transmission electron microscopy, analyses of water species concentration and trace element distribution in quartz, as well as with microstructures in plagioclase, to determine their characteristics and elucidate their timing and mechanisms of formation relative to the deformational history. Medium-dark grains are primarily located in and near kilometer-scale shear zones at the margins of the Parry Sound domain, have notably darker cores than most samples in the interior, and may have higher water contents than other samples in the interior. These grains formed during late shearing, at a lower temperature than CL-bright grains; they thus provide evidence that the large shear system narrowed with time. Dark mantles occur at grain boundaries and correlate with higher concentrations of Fe. They formed after the first shearing event, but while still at amphibolite facies, and they provide evidence for post-kinematic alteration at grain boundaries. Dark sinuous lines correspond to subgrain boundaries that formed after retrograde shearing, but while still at amphibolite facies. Dark straight lines correspond to fluid inclusion trails and most likely formed at low temperatures and pressures during exhumation.
The Pele Offset Dykes, Sudbury impact structure, Canada
(Canadian Science Publishing, 2017-11-08) Pilles, Eric A.; Osinski, Gordon R.; Grieve, Richard A.F.; Coulter, Adam B.; Smith, David; Bailey, Joshua
The Offset Dykes are impact-melt bearing dykes related to the 1.85 Ga Sudbury impact structure. Currently, the dykes extend radially outward from – or occur concentrically around – the Sudbury Igneous Complex, which is the remnant of a differentiated impact melt sheet and the source of the dykes. The recently identified three Pele Offset Dykes intrude into the Archean rocks north of the Sudbury Igneous Complex. In this study, the Pele dykes are characterized for the first time by a combination of fieldwork, optical microscopy, electron microprobe analyses, and bulk geochemical analyses. The Pele Offset Dykes stand out from the other Offset Dykes at Sudbury in two significant ways: (1) All other known Offset Dykes consist of an inclusion-rich lithology in the centre of the dyke and an inclusion-poor lithology along the margins. The Pele dykes, however, are only composed of the inclusion-poor phase. (2) The Pele dykes – particularly the Central and Eastern dykes – have a more evolved chemical composition relative to the other Offset Dykes. These observations suggest that the Pele dykes were emplaced after the other known Offset Dykes during two injection events: the Western followed by the Central and Eastern Pele dykes.
Water budget, performance of evapotranspiration formulations, and their impact on hydrological modeling of a small boreal peatland-dominated watershed
(Canadian Science Publishing, 2017-11-03) Isabelle, Pierre-Erik; Nadeau, Daniel F.; Rousseau, Alain; Anctil, Francois
Peatlands occupy around 13% of the land cover of Canada, and thus play a key role in the water balance at high latitudes. They are well known for having substantial water loss due to evapotranspiration. Since measurements of evapotranspiration are scarce over these environments, hydrologists generally rely on models of varying complexity to evaluate these water exchanges in the global watershed balance. This study quantifies the water budget of a small boreal peatland-dominated watershed. We assess the performance of three evapotranspiration models in comparison with in situ observations and the impact of using these models in the hydrological modeling of the watershed. The study site (~1-km2) is located in the Eastern James Bay lowlands, Québec, Canada. During summer 2012, an eddy flux tower measured evapotranspiration continuously, while a trapezoidal flume monitored streamflow at the watershed outlet. We estimated evapotranspiration with a combinational model (Penman), a radiation-based model (Priestley-Taylor), and a temperature-based model (Hydro-Québec), and performed the hydrological modeling of the watershed with HYDROTEL, a physically-based semi-distributed model. Our results show that the Penman and Priestley-Taylor models reproduce the observations with the highest precision, while a substantial drop in performance occurs with the Hydro-Québec model. However, these discrepancies did not appear to reduce the hydrological model efficiency, at least from what can be concluded from a 3-month modeling period. HYDROTEL appears sensitive to evapotranspiration inputs, but calibration of model parameters can compensate for the differences. These findings still need to be confirmed with longer modeling periods.
Criteria for the recognition of Archean calc-alkaline lamprophyres: examples from the Abitibi Subprovince
(Canadian Science Publishing, 2017-10-18) Mathieu, Lucie; Bouchard, Émile; Guay, Francis; Liénard, Alizée; Pilote, Pierre; Goutier, Jean
Lamprophyres are minor intrusions with atypical sources and crystallisation sequences. Among lamprophyres, the calc-alkaline type (CAL) on which this study focuses has the least distinctive chemistry and petrology. CAL correspond to small-volume mafic intrusions characterised by the early fractionation of amphibole and/or biotite. In the Archean Superior Province (Canada), CAL are temporally and spatially related to several gold deposits and may thus be relevant to mineral exploration. This study focuses on several altered and metamorphosed intrusions of the Abitibi and La Grande Subprovinces, which were designated lamprophyres based on field observations. Several criteria established from thin sections, whole-rock chemical analyses and SEM data are applied to the studied rocks in order to distinguish CAL from other types of magma. As a result, only one of the studied dykes has the morphology, chemistry, and petrology typical of CAL, while the other intrusions are either too altered to be classified or may correspond to metamorphosed and metasomatized gabbro and diorite. This study shows that thin sections and whole-rock chemical analyses are not always sufficient to unequivocally classify an altered and metamorphosed intrusion as a CAL. Also, intrusions as challenging to recognise as CAL should not be used by exploration geologists to prospect for orogenic gold deposits. Much remains to be done to document the distribution and volume represented by lamprophyres in Archean greenstone belts and to confirm their spatial dependence with gold deposits.
Eemian estuarine record forced by glacio-isostasy (S Iceland) - link with Greenland and deep sea records
(Canadian Science Publishing, 2017-10-24) Van Vliet-Lanoë, Brigitte; Schneider, Jean-Luc; Gudmundsson, Agust; Guillou, Hervé; Nomade, Sébastien; Chazot, Gilles; Liorzou, Céline; Guegan, Solène
Central southern Iceland is one of the main outlets of the Icelandic Ice Sheet where a MIS 5e sedimentary complex, the Rangá Formation, is extensively observed below the last deglaciation terminal moraines. Sedimentary facies demonstrate that the Rangá Formation is mostly tidal, up to 215 m (transgression I) and 168 m (transgression II) in altitude. The first highstand reworks a thick tephra from the Grimsvötn volcano, known in marine cores as 5e low/Bas-IV and positioned at ca. 127 Ka BP, the Eemian thermal optimum. This formation is related to a rapid deglaciation followed by two marine transgressions marked by the development of extended mud flats, which were separated by a complex regression phase, associated with loess deposition, ca. 9 Ka in duration. Palaeo jökulhlaups, basaltic flows, and tephra fallouts from the Hekla and Grimsvötn volcanoes affected the sedimentation. The Rangá Formation yields one of the first continuous and complete estuarine records of the Eemian interglacial in Iceland and probably for most of the northern terrestrial Atlantic. This estuarine infill records the distal signature of a complex glacial advance within the last interglacial, already well identified in northern and central Iceland. The glacial advance is attributed to the intra-Eemian cooling events (Greenland GS 26 or marine cold events M-C25-C26). It is followed by a warming and a glacial retreat corresponding to the Greenland GI 25 event. This formation allows, in connection with the timing of recognized volcanic periods, a better insight of the interconnections between sea-level, regional glacial extent, and Northern Hemisphere marine and ice core climatic records.
Recent sedimentation in three adjacent fjord-lakes on the Québec North Shore (Eastern Canada): facies analysis, laminae preservation and potential for varve formation
(Canadian Science Publishing, 2017-10-11) Nzekwe, Obinna Peter; Francus, Pierre; St-Onge, Guillaume; Lajeunesse, Patrick; Fortin, David; Poiré, Antoine G.; Philippe, Edouard G. H.; Normandeau, Alexandre
This paper analyzes short gravity cores sampled along transects in three adjacent deep fjord-lakes (lakes Pentecôte, Walker, and Pasteur) on the Québec North Shore, eastern Canada, to evaluate the distribution of laminated sediments and potential for varve formation. Facies analysis based on lithological description, digital photos, CT-scan images, and bathymetric data allowed for the identification of four main sediment facies, namely laminated sediments, partially laminated sediments, bioturbated sediments, and massive sediments. Direct evidence that Lake Walker undergoes thermal stratification was monitored from 2014 to 2016. Mean sedimentation rates and sedimentation fluxes of postglacial sediments in the distal basin of the three studied lakes are ≤0.12 cm a−1 and 0.03–0.16 g cm−2 a−1, respectively, based on 210Pb, 137Cs, and AMS radiocarbon dating. On the basis of thin section image analysis and 210Pb (CIC) chronology model, Lake Pentecôte contains mainly massive, partially laminated sediments, while Lake Pasteur contains partially laminated sediments and non-annual varve-like sediments. However, Lake Walker contains laminated sediments that are likely varves. The increased potential for laminae preservation observed in Lake Walker compared to lakes Pentecôte and Pasteur is associated with more favourable morphological characteristics including higher relative depth, mean depth, maximum depth, and topographic exposure.
Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns
(Canadian Science Publishing, 2017-11-08) Sheffield, Sarah L; Ausich, William I.; Sumrall, Colin D.
Hirnantian (latest Ordovician) localities containing echinoderm fossils are rare; the few that have been discovered primarily contain disarticulated crinoid ossicles. Therefore, relatively little is known about echinoderm evolutionary dynamics across the Late Ordovician – early Silurian boundary, especially noncrinoid echinoderms. New diploporitan echinoderms, Holocystites salmoensis and an unidentified holocystitid, from reefal facies of the Upper Ordovician Ellis Bay Formation of Anticosti Island provide a critical data point concerning diploporitan biogeography and evolutionary pathways undertaken during the Ordovician and Silurian. These fossils also provide a crucial link in understanding the ancestry of the Silurian Holocystites Fauna, an unusual diploporitan fauna from the middle Silurian of North America, whose origination dates back at least 15 million years earlier than previously thought with the discovery of taxa described here. New fossil data such as these stress the importance of uncovering new localities from underrepresented times and places in Earth’s history, so that these evolutionary transitions can be better understood.

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