Search

The Cretaceous High Arctic Large Igneous Province (HALIP) in Canada, although dominated by tholeiites (135–90 Ma), contains two main groups of alkaline igneous rocks. The older alkaline rocks (∼96 Ma) scatter around major fault and basement structures. They are represented by the newly defined Fulmar Suite alkaline basalt dykes and sills, and include Hassel Formation volcanic rocks. The younger alkaline group is represented by the Wootton Intrusive Complex (92·2–92·7 Ma), and the Audhild Bay Suite (83–73 Ma), both emplaced near the northern coast of Ellesmere Island. Fulmar Suite rocks resemble EM-type ocean island basalts (OIB) and most show limited crustal contamination. The Fulmar Suite shows increases of P2O5 at near-constant Ba–K–Zr–Ti that are nearly orthogonal to predicted fractionation- or melting-related variations, which we interpret as the result of melting composite mantle sources containing a regionally widespread apatite-bearing enriched component (P1). Low-P2O5 Fulmar Suite variants overlap compositionally with enriched HALIP tholeiites, and fall on common garnet lherzolite trace element melting trajectories, suggesting variable degrees of melting of a geochemically similar source. High-P2O5 Hassel Formation basalts are unusual among Fulmar rocks, because they are strongly contaminated with depleted lower crust; and because they involve a high-P2O5–Ba–Eu mantle component (P2), similar to that seen in alkali basalt dykes from Greenland. The P2 component may have contained Ba–Eu-rich hawthorneite and/or carbonate minerals as well as apatite, and may typify parts of the Greenlandic sub-continental lithospheric mantle (SCLM). Mafic alkaline Audhild Bay Suite (ABS) rocks are volcanic and hypabyssal basanites, alkaline basalts and trachy-andesites, and resemble HIMU ocean island basalts in having high Nb, low Zr/Nb and low 87Sr/86Sri. These mafic alkaline rocks are associated with felsic alkaline lavas and syenitic intrusions, but crustally derived rhyodacites and rhyolites also exist. The Wootton Intrusive Complex (WIC) contains geochemically similar plutonic rocks (alkali gabbros, diorites and anatectic granites), and may represent a more deeply eroded, slightly older equivalent of the ABS. Low-P2O5 ABS and WIC alkaline mafic rocks have flat heavy rare earth element (HREE) profiles suggesting shallow mantle melting; whereas High-P2O5 variants have steep HREE profiles indicating deeper separation from garnet-bearing residues. Some High-P2O5 mafic ABS rocks seem to contain the P1 and P2 components identified in Fulmar–Hassel rocks, whereas other samples trend towards possible High-P2O5 + Zr (PZr) and High-P2O5 + K2O (PK) components. We argue that the strongly alkaline northern Ellesmere Island magmas sampled mineralogically heterogeneous veins or metasomes in Greenlandic-type SCLM, which contained trace phases such as apatite, carbonates, hawthorneite, zircon, mica or richterite. The geographically more widespread apatite-bearing component (P1) could have formed part of a heterogeneous plume or upwelling mantle current that also generated HALIP tholeiites when melted more extensively, but may also have resided in the SCLM as relics of older events. Rare HALIP alkaline rocks with high K–Rb–U–Th fall on mixing paths implying strong local contamination from either Sverdrup Basin sedimentary rocks or granitic upper crust. However, the scarcity of potassic alkaline HALIP facies, together with the other trace element and isotopic signatures, provides little support for a ubiquitous fossil sedimentary subduction-zone component in the HALIP mantle source. [ABSTRACT FROM AUTHOR]

New occurrences of Psammichnites gigas are reported from the Mackenzie Mountains, northwest Canada. A locality in the hanging wall of the Plateau Fault, just below the top of the upper member of the Backbone Ranges Formation, demonstrates that the uppermost part of the unit is Tommotian (latter part of Cambrian Age 2) or possibly earliest Atabanian (earliest Cambrian Age 3) in its previously undated proximal manifestation. Localities in the trilobite-bearing Sekwi Formation confirm that Psammichnites gigas can be at least as young as Atdabanian (early to middle parts of Cambrian Age 3) in Laurentia. A review of reported occurrences suggests Psammichnites gigas, and the related ichnotaxa Plagiogmus arcuatus and Taphrelminthopsis circularis, may be valuable for correlations in western Laurentia if their ichnotaxonomic relationships are clarified. [ABSTRACT FROM AUTHOR]

Studies the distribution and characteristics of Taconian and Acadian deformation in the southern Quebec Appalachians. Subdivision of Taconian orogen; Structural relationships of Cambro-Ordovician rocks; Structural synthesis and interpretation; Tectonic zonation of the Quebec Appalachians.

Proposes the possibility of a collision between Laurentia and Gondwana throughout the Paleozoic Era. Neoproterozoic rifting; Reconstructions of major continents from the Cambrian to early Ordovician and Devonian periods; Origin of the Appalachian and Andean mountain system; Implications of a complex Wilson cycle.

Colonial Rugosa and Tabulata from the lower and middle Viséan Flett Formation of the Liard Basin (Canada) are described. Michelinia expansa is the first tabulate coral described from the Flett Formation. The new generic name Cordilleria is introduced for the North American Lithostrotionidae and its differences from the European Siphonodendron are documented. Extremely wide variability in all characters and the small size of the studied collection allowed description of numerous Liard Basin specimens in open nomenclature only. Discussion of the most important characteristics of Cordilleria gen. nov. forms an introduction to the comprehensive revision of the North American Lithostrotionidae. The state of preservation of a colony identified as Stelechophyllum cf. banffense emphasizes the necessity of recognizing the diagenetic alterations of specimens prior to their taxonomic identification. [ABSTRACT FROM AUTHOR]

Cyclic‐step bedforms typifying a Froude‐supercritical flow regime are a recurrent component of depositional/erosional turbiditic systems. Over modern delta slopes, cyclic steps have been inferred from observations of upslope‐migrating crescent‐shaped bedforms. However, the recognition in the sedimentary record of the resulting stratal pattern and depositional facies remains challenging. In this study, the depositional facies observed in exposed late Quaternary glaciofluvial upper delta‐slope sands (Portneuf‐Forestville, Québec) are compared to those cored from a modern analogue consisting of sediment waves interpreted as cyclic steps (Southwind Fjord, Baffin Island). The fossil and modern delta slopes share similar context, morphology and stratigraphic record. The clinoform foresets dip 2 to 6° and consist of prevailing sand‐sized material including subhorizontal to upslope‐dipping top‐cut‐out turbidites. Individually, the latter are 5 to 20 cm thick and massive to planar laminated (prevailing TA and TB subdivisions). In the fossil delta slope, related successions form relatively thick, well‐bedded suites, which are truncated downcurrent by, and onlap upstreamward on, inclined composite erosion surfaces here referred to as pseudo‐foresets. Pseudo‐foresets are regularly spaced (10 to 30 m) and have dips greater than the clinoform foresets (ca 20°). Large composite scours form pseudo‐channel structures filled in by structureless pebbly sand deformed by sheared flame structures, in association with coarse sand showing undulating lamination and rip‐up clasts. Similar depositional facies are observed on the modern delta slope. The stratal pattern is best compatible with upslope‐migrating bedforms and structureless sand indicates hydraulic jump deposits typical of cyclic steps. Cyclic‐step flow events, encompassing a succession of genetically linked erosional cyclic steps, depositional cyclic steps and subsequent waning‐flow conditions, were associated with the dense basal layer of high‐density (stratified) turbidity currents. They are specifically associated with pseudo‐channel incision and infill. The deposition of well‐bedded suites on the stoss side, occasionally also on the lee side, is interpreted to result from a different type of turbidity current, which decelerated over the bedform stoss and accelerated over the lee sides of pre‐existing cyclic‐step morphologies. Antidunal flow conditions in expanded (non‐stratified) turbidity currents are tentatively suggested, deposition being linked, in this case, to interactions between inherited bedform morphologies and a near‐bed tractive layer. In the resulting dual flow model, the bulk of delta‐slope sands was mainly deposited from turbidity currents not developing a cyclic‐step instability, yet cyclic steps were instrumental in shaping and/or re‐organizing the delta‐slope morphology, bedforms and resulting stratal patterns. In some delta systems, the upslope migration of supercritical crescentic bedforms may not only be due to repetitive cyclic steps but could also result from antidunal turbidity current conditions remobilizing an inherited cyclically‐stepped morphology. [ABSTRACT FROM AUTHOR]

Bimodal volcanism occurs in a range of extensional environments that are characterized by distinctive but overlapping, lithogeochemical and isotopic signatures and lithological assemblages. Where basaltic magmatism is associated with ferroan (A‐type) rhyolites, it is typically the lithogeochemistry and isotopic systematics of the basaltic rocks that are the most beneficial in constraining the tectonic evolution. This study presents geochemical and isotopic data from mafic volcanic rocks of the bimodal Aillik Group, that formed during the assembly of the Paleoproterozoic supercontinent Nuna. Lithogeochemical signatures define two suites. Suite 1 samples have N‐MORB (Normal‐Mid‐Ocean Ridge Basalt) chemical affinities such as flat HREE, and smooth but flat LREE and have εNd(t = 1860 Ma) values between +2.8 and +4.8. Suite 2 samples typically have compositions between N‐MORB and IAT (Island Arc Tholeiites) basalts, with variable REE patterns ranging from IAT to OIB (Ocean Island Basalt). The basalts display moderately developed subduction zone signatures, such as negative Nb and Ti, and have εNd(t = 1860 Ma) ranging from −3.4 to +2.2. Geochemical variability within the Aillik Group mafic rocks is explained by processes active in arc settings and involves mixing between depleted mantle components with variable contributions from crustal and subducted‐slab sources. Coupled with field evidence, the geochemical and isotopic data support emplacement of the basalt in an extensional, backarc basin setting. This backarc basin formed due to localized extension during Nuna assembly. The Makkovik Province preserves a complex orogen characterized by multiple diachronous, compressional, and extensional events along a long‐lived active margin of the Archean North Atlantic Craton. Key Points: Protracted assembly of the Paleoproterozoic supercontinent Nuna resulted in a localized extension in an overall compressional settingBackarc settings produce geochemical and isotopic variability in mafic volcanic rocks that obscure understanding of their tectonic settingPaleoproterozoic accretionary orogens comprise multiple diachronous, compressional, and extensional events along a long‐lived active margin [ABSTRACT FROM AUTHOR]

The Great Unconformity is a widely distributed surface separating Precambrian rocks from overlying Phanerozoic sedimentary sequences. The causes and implications of this feature, and whether it represents a singular global event, are much debated. Here, we present new apatite (U-Th)/He (AHe) thermochronologic data from the central Canadian Shield that constrain when the Precambrian basement last cooled to near-surface temperatures, likely via exhumation, before deposition of overlying early Paleozoic sedimentary sequences that mark the Great Unconformity. AHe data from 11 samples (n = 57) across a broad region define a similar date-eU pattern, implying a common thermal history. Higher eU (>25 ppm) apatite form distinct flat profiles of reproducible dates at ∼510 ± 49 Ma (mean and 1σ standard deviation), while lower eU (<25 ppm) apatite define a positive date-eU trend with younger dates. The data patterns, geologic context, and thermal history modeling point toward >3 km of erosion across the entire ∼450,000 km2 study area between 650 and 440 Ma, followed by modest reheating during later burial. Plume activity associated with intracratonic basin formation or continental rifting/breakup may have caused this erosion event. The post-650 Ma timing of the last major sub-Great Unconformity exhumation phase in this region implies a late Great Unconformity that is younger than inferred elsewhere in North America. This suggests that this feature is likely the result of multiple temporally distinct erosion events with differing footprints and mechanisms. [ABSTRACT FROM AUTHOR]

The presence of lamination on sedimentary rocks is a distinct characteristic, particularly in shales. They are distinct due to the contrast between successive layers with regard to grain size, composition, color, and sedimentary structures, such as graded beds. Typically, the degree of lamination is controlled by the sedimentation rate and flow regime. Herein, we developed a mudstone classification scheme in terms of lamination because lamination-based shale facies are related to differing features in mineral composition, porosity, and Young's modulus. This study also attempts to verify whether wireline log patterns are relevant to shale lithofacies. The relationship between the porosity and lamination of the Montney Formation can be used to estimate reservoir properties. Our results show that an increased silt lamina in mudstone leads to an increase in the quartz and calcite contents and a decrease in the clay content, which increases the porosity, permeability, and Young's modulus. However, reservoir quality is not solely dependent on lamination because of the complex interaction between components. The degree of lamination affected the neutron, density, and sonic log responses. Furthermore, the presence of lamination tends to decrease the neutron percentage, with similar trends in density and sonic log box plots in the study area. When the percentage of clay or cement material decreases, the neutron and density log responses diminish. Meanwhile, when the rock texture variation increases with an increase in the degree of lamination, the sonic log response decreases. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

River temperature exerts a critical control on habitat for aquatic biota. As the climate warms in eastern Canada, threats to habitats of cold‐water species will increase, underpinning the necessity to develop an understanding of landscape‐scale, thermal regimes of flowing waters. We assessed the performance of spatial statistical network (SSN) models of river temperature using high‐resolution thermal infrared imagery (0.6 m) and LiDAR (1 m) compared to NASA's Shuttle Radar Topography Mission (SRTM—30 m) topographic data and interrogate LiDAR derived fine‐scale models (3 ha) to describe groundwater connectivity to surface waters in catchments with shallow overburden and varied bedrock geology. LiDAR improved model performance in a catchment underlain by a homogeneous, high hydraulic conductance bedrock (Cains River) but did not improve model performance in a catchment with heterogeneous bedrock and variable hydraulic conductance (North Pole Stream). We hypothesize that differences in bedrock conductance modified topographic controls on subsurface flows and discharge patterns to the rivers and thus produced the mixed performance of the SSN models. At finer scales, river reaches in steep valleys incising high conductance bedrock produced groundwater discharge, which was absent in incised valleys with low conductance bedrock. These findings indicate that while topography exerts an important control on landscape‐scale hydrological processes, geologic setting is a similarly important influence on hydrological processes. We suggest the inclusion of a third dimension of spatial autocorrelation, representative of the vertical plane that captures the geologic setting, would broaden the geographic applicability of spatial statistical models for river temperature studies. Key Points: Spatial statistical river network models had mixed success in predicting river temperature in differing geologic and topographic settingsValley incision in shallow, high hydraulic conductance bedrock facilitated groundwater discharge associated with cool river temperaturesValley incision in shallow, low hydraulic conductance bedrock limited groundwater discharge and was associated with warm river temperatures [ABSTRACT FROM AUTHOR]

Colonies of the rugose corals Nemistium liardense sp. nov. and Heritschioides simplex sp. nov. were collected from limestone in the upper member of the Mattson Formation in the Liard Range in the Northwest Territories and are the only known identifiable coral species from the Mattson Fm. The Mattson Fm., deposited in the Liard Basin west of the syndepositional Bovie reverse fault, comprises sandstone with subordinate shale and carbonates deposited during several delta cycles. The close morphological similarity and identical mode of offsetting in N. liardense colonies from the Mattson Fm. and the allochthonous Stikine Terrane of British Columbia indicate they belong in the same species. This and the morphological similarity between H. simplex and the late Serpukhovian to early Bashkirian H. columbicum allow assignment of the coral-bearing part of the upper Mattson Fm. to Bashkirian Foraminiferal Biozone 20. Widespread occurrence of the genus Nemistium confirms open communication between the Liard Basin region and the western European and northern African seas. [ABSTRACT FROM AUTHOR]

Large Igneous Provinces (LIPs) are emerging as a significant driver of short duration climatic change including mass extinctions. Here we compare the record of LIPs against the timing of Devonian biotic crises that are well recorded in the numerous anoxia events throughout this period. The largest LIPs are two-pulse events at ca. 370 and ca. 360 Ma that are present in both Siberia (Yakutsk-Vilyui LIP) and Baltica (Kola-Dnieper LIP) and correlate with the Kellwasser anoxia events (late Frasnian) and Annulata or Dasberg and Hangenberg anoxia events in the late/latest Famennian. The regionally significant Altai Sayan LIP is only approximately dated at c.400 Ma and within uncertainties could be linked to either (or both?) the c. 405 Ma Chebbi or Atopus anoxia events near the basal Emsian (associated with graptolite extinction) or the c. 385–390 Ma group of anoxia events in the Eifelian or Givetian. Additional magmatic events that are less precisely dated are: 1) the c. 400–345 Ma Kedon magmatism of the Omolon craton, possibly linked with the Yakutsk-Vilyui event, 2) 380–330 Ma Maritimes (Magdalen) basin event of the Appalachian region of eastern Canada and adjacent US, 3) middle-late Devonian Selwyn basin alkaline magmatism of northwestern Canada, and 4) the Ordovician - late Silurian- possibly Devonian Soltan Maidan event Iran. However, more precise dating is required for each of these magmatic events before they can be properly compared with the Devonian biotic crisis record. • Pulses of 380–360 Ma Yakutsk-Vilyui & Kola-Dnieper LIPs linked with late Frasnian and middle/late Famennian anoxia events • Ca. 400 Ma Altay-Sayan LIP correlated withearly Devonian biotic crises. • Other magmatic events (Soltan Maidan, Magdalen, Selwyn basin) need precise dating to evaluate any anoxia links [ABSTRACT FROM AUTHOR]

Colonies of the rugose corals Nemistium liardense sp. nov. and Heritschioides simplex sp. nov. were collected from limestone in the upper member of the Mattson Formation in the Liard Range in the Northwest Territories and are the only known identifiable coral species from the Mattson Fm. The Mattson Fm., deposited in the Liard Basin west of the syndepositional Bovie reverse fault, comprises sandstone with subordinate shale and carbonates deposited during several delta cycles. The close morphological similarity and identical mode of offsetting in N. liardense colonies from the Mattson Fm. and the allochthonous Stikine Terrane of British Columbia indicate they belong in the same species. This and the morphological similarity between H. simplex and the late Serpukhovian to early Bashkirian H. columbicum allow assignment of the coral-bearing part of the upper Mattson Fm. to Bashkirian Foraminiferal Biozone 20. Widespread occurrence of the genus Nemistium confirms open communication between the Liard Basin region and the western European and northern African seas. [ABSTRACT FROM AUTHOR]

Purpose: Sediment fingerprinting is increasingly being used to improve the understanding of sediment dynamics within the critical zone and provide information that can help guide management decisions at the watershed scale. The objectives of this study were to investigate both the implications of different sediment fingerprinting sampling designs and spatial scales on the characterization of sediment dynamics in a predominantly agricultural watershed in northwestern New Brunswick, Canada. Materials and methods: Color and radionuclide fingerprints were used to discriminate between three potential sediment sources: agricultural topsoil, agricultural streambanks, and forested areas (topsoil and streambanks). Suspended sediment was collected seasonally, between 2008 and 2014, at five sites with drainage areas ranging from 3.0 to 13.4 km2. Using the same source and sediment data set, multiple-, nested-, and local-location fingerprinting sampling designs were employed to investigate the influence of scale of observation, geomorphic connectivity, land use, and the heterogeneity of source fingerprints on apportionment results. Results and discussion: Sediment collected in the headwaters was primarily derived from forested areas while the sediment collected at the outlet of the watershed was primarily from agricultural topsoil. When comparing the multiple- and nested-location designs, it was found that accounting for the spatial variability in the fingerprint properties of each source had a small difference in the sediment apportionment results. Furthermore, the local-location design demonstrated that the sediment collected at each location was composed of predominately local sources as opposed to upstream sediment entering the local catchment. Conclusions: Assessment of the sources of sediment at a range of spatial scales better accounts for both geomorphic connectivity and differences in land use throughout the watershed. Overall, each of the three fingerprinting sampling designs provided different information that can be used to guide soil and water conservation management. [ABSTRACT FROM AUTHOR]

When glacial cycles occur above low‐permeability geologic formations, such as the shale and limestone units being considered for nuclear waste disposal in Canada, pressures may differ greatly from normal hydrostatic conditions. Although shale also often has the propensity to generate separate phase fluids like natural gas, it is largely uncertain how the processes that control this behavior might affect water pressure evolution during glacial loading cycles. Therefore, this study investigates the relationships among these system components via an example site that exhibits both a dramatic underpressure and potential evidence for gas phase methane in situ. A simple 1‐D representation of the site was constructed, and hydromechanical coupling during a glacial cycle was simulated with and without gas phase methane present. Results indicate that, while the presence of gas phase dampened the effects of the loading cycle due to its higher compressibility compared to water, it did not preclude underpressure development. Plain Language Summary: To protect water resources from contamination, many countries are planning to store nuclear waste underground within very tight layers of rock. To assess the safety of this strategy, we must understand how fluids might move through these rock layers over long periods of time. Anomalous pressures in low‐permeability rocks offer clues into long‐term flow processes, but natural gas complicates the pressure evolution. Therefore, in this study we performed mathematical simulations of water flow under the influence of glacial forces, with and without natural gas present. While gas phase somewhat counteracted the glacial effects due to its higher compressibility, underpressures similar to the measured values were still produced in both single‐phase and multiphase simulations. These results help to improve our understanding of the processes that might occur within the rocks at nuclear waste repository sites after they are built, thus protecting humans from potential contamination. Key Points: Vertical stresses from both ice weight and crustal flexure were incorporated in a 1‐D model of a proposed nuclear waste repository siteGas phase dampened the effects of glacial loading on simulated long‐term water pressure evolution at the proposed repository siteHydromechanical coupling could have led to underpressure in shale at the site, even if gas phase methane is assumed to be present in situ [ABSTRACT FROM AUTHOR]

Structural equation modeling (SEM) was applied here to modify the ordinary weights-of-evidence (WofE) method for calculating posterior probability to improve conditional independence (CI) in the application of this method mineral potential prediction. The new method attempts to reduce the effect of CI by defining new binary patterns with an optimum combination of cutoff values of patterns. The solution is calculated through SEM, and the goodness of fit between evidence and mineral deposit occurrences is evaluated by a specified target function. The main difference between the new WofE and ordinary WofE is that evidence in the new method maintains a balance between the significance for mineral potential prediction and CI, rather than the significance for mineral prediction only as in ordinary WofE. A case study of prediction of potential for hydrothermal Au mineral deposits in Nova Scotia, Canada, is discussed here. The results indicate that the new method performs better than the ordinary WofE. [ABSTRACT FROM AUTHOR]

The article focuses on the mineral poudretteite which was first collected from the Poudrette quarry on Mont Saint-Hilaire, Canada but superior quality was harvested from Myanmar. It talks about the geological description of the area in Myanmar being responsible for the quality of the mineral which was superior than the ones found in Canada.

We present a multi‐chronometric approach for reconstructing deep‐time thermal histories using southern Baffin Island as a case study. This continuous thermal history begins with the Palaeoproterozoic Trans‐Hudson Orogeny and is derived from inverse and forward models that integrate thermochronometers spanning some 500°C: new apatite U–Pb ages and K‐feldspar 40Ar/39Ar multi‐diffusion domain data, published (U–Th)/He zircon ages and new multi‐kinetic fission‐track results. Integration of data from a wider temperature range reduces ambiguities in thermal‐history modelling and permits us to constrain the timing of geological processes including, extended post‐orogenic cooling, enhanced later Proterozoic cooling, and then episodic burial and exhumation in the Palaeozoic–Mesozoic. [ABSTRACT FROM AUTHOR]

Investigations of glacial sediment exposures in a former open pit in the Pine Point Mining District, Northwest Territories, reveal evidence of changes in stress magnitude as exhibited by the movement of deformation 'fronts' within subglacial tills, as evident through micromorphological analysis. Indications of deformation, driven by stress fluctuations, were observed throughout a set of vertical subglacial till samples associated with the Laurentide Ice Sheet. These tills exhibit multiple sub‐lithofacies variations in concert with marked changes in microshear orientation, which can be directly related to changing stress levels within a subglacial deforming bed. The evidence of changes in till stress conditions is typical of subglacial tills occurring beneath an active temperate ice mass within a soft deforming bed. As differing 'layers' of till that form a mosaic‐like pattern become immobilized and 'detached' subjacent to the deforming bed sediments, a signature of this action is recorded within the tills as sequences of specific microstructures. These microstructures are part of a spectrum of micro‐forms that develop as consequence of changes in stress, porewater content and clay content within the 'fault‐gouge'—like environment formed beneath an active temperate ice sheet. A model is developed that uses data from Pit O‐28 demonstrating where deformation 'boundary front' evidence in the form of deformation bands has developed as basal driven stress levels have penetrated active deforming sediments. The evidence from Pine Point indicates that till acts as an excellent palaeo‐strain record of past active glacial processes, subglacial basal thermal conditions and sediment mobility. [ABSTRACT FROM AUTHOR]

Subfamily Microcyclinae Plusquellec, 2006 is promoted to family rank. A new family, genus and species, Devonodiscidae, Devonodiscus and D. latisubex are named. Combophyllum multiradiatum Meek, 1868, which is based on a specimen from an unknown Mackenzie Valley location and formation, is assigned to Devonodiscus and redescribed using specimens from accurately known formations and locations. Glossophyllum discoideum Soshkina, 1936, from the Eifelian of the Ural Mountains, is also assigned to Devonodiscus. Six other species, previously placed in either Combophyllum, Palaeocyclus, Microcyclus, Hadrophyllum or Chonophyllum, may belong to Devonodiscus. New topotypic material of one of these, Hadrophyllum wellingtonense Packham, 1954 is illustrated. In late ontogeny Devonodiscus latisubex and D. discoideum (Soshkina) commonly modified their corallum to become cylindrical with a cystiphylloid-like interior. Glossophyllum discoideum may regain a discoid morphology, making the corallum pulley-shaped. Such changes were probably caused by disruptions to bedding surfaces on which the corals developed. An unrelated coral, originally named Actinocystis versiformis is discoid becoming cylindrical after disruptions caused by increased water-depth. New specimens from the type locality in the central Western Urals are described and illustrated as Digonophyllum versiforme (Markov, 1923). The species' complicated taxonomy and synonymy are attempted. High resolution stratigraphy indicates Devonodiscus multiradiatus to be confined to the middle Eifelian Eoschuchertella adoceta benthic assemblage and australis conodont zones, and D. latisubex to the late Eifelian upper Carinatrypa dysmorphostrota benthic assemblage and upper kockelianus conodont zones. Canadian discoid corals add further evidence that northwestern continental Canada and Northern Urals belonged to the same faunal province in late Eifelian time. [ABSTRACT FROM AUTHOR]

In Eastern Canada, groundwater is the main water supply for most of the rural regions and in many large urban communities. An understanding of the impacts of climate change on this resource is crucial for sustainable water management in this region. The objectives of this paper was to summarize the state of knowledge about possible climate change impacts on groundwater dynamics in Eastern Canada, thus providing a clearer understanding of future conditions. Twenty-two studies are reviewed including Ontario, Québec, New Brunswick, Nova Scotia, and Prince Edward Island, to identify the impacts on groundwater recharge and river baseflows. The studies disagree in their estimates of changes in future recharge conditions, and no trend from West to East was revealed. This could be due to the use of different modelling approaches (model type, climate change scenario, future horizon). Nonetheless, more inter-annual variability during the summer and earlier snowmelt periods causing seasonal shifts in the recharge cycle are expected. The studies show that base flows could decrease, which could induce critical conditions for water supplies and for ecosystems. This review provided new insights that lead to the following recommendations for future studies: 1) use a variety of climate models and emission scenarios; 2) promote the use of integrated models when possible; 3) study long-term climate change impacts on groundwater resources at different scales; 4) simulate the combined effects of climate change and other pressures; and 5) develop models that cover other regions of Eastern Canada as dictated by stakeholders and water managers. [ABSTRACT FROM AUTHOR]

Focuses on the early history of vertebrate paleontology in Canada. Recognition of the potential of fossil resources in the area; Contribution of geologist Loris Russel to paleontological record; Study of the Cenozoic mammal faunas.

Defining temperature at depth to identify geothermal resources relies on the evaluation of the Earth heat flow based on equilibrium temperature measurements as well as thermal conductivity and heat generation rate assessment. Such high-quality geothermal data can be sparse over the region of interest. This is the case of the St. Lawrence Lowlands sedimentary basin covering 20,000 km2 to the south of Québec, Canada, and enclosing only three wells up to a depth of 500 m with equilibrium heat flow measurements. However, more than 250 oil and gas exploration wells have been drilled in this area, providing for this study (parce que c'est 93 sinon) 81 locations with bottom-hole temperature up to a depth of 4300 m, however, not at equilibrium. Analyzing these data with respect to the deep geothermal resource potential of this sedimentary basin requires evaluating the thermal conductivity and heat generation rate of its geological units to properly extrapolate temperature downward. This was done by compiling literature and recent thermal conductivity measurements in outcrop and core samples as well as new heat generation rate estimates from spectral gamma ray logs to establish a first thermal assessment of geological units deep down into the basin. The mean thermal conductivity of the thermal units varies from 2.5 to 6.3 W/m·K, with peak values in the basal sandstones, while the heat generation rate varies from 1.6 to 0.3 µW/m3, decreasing from the upper caprocks toward the base of the sequence. After correcting the bottom-hole temperatures for drilling disturbance with the Harrison correction and subsequently for paleoclimate variations, results indicate a mean geothermal gradient of 23.1 °C/km, varying from 14 to 40 °C/km. Evaluating the basin thermal state from oil and gas data is a significant challenge facilitated by an understanding of its thermal properties. [ABSTRACT FROM AUTHOR]

The 28-km diameter Tunnunik impact structure in northern Victoria Island, Arctic Canada, was mapped using ASTER, Landsat 8, RADARSAT-2 polarimetric synthetic aperture radar (SAR), and Quickbird data. Multispectral analysis was accomplished through band ratios, MNF transform, and spectral matching algorithms, from which 4 distinct spectral units were defined. Polarimetric SAR decompositions also showed different scattering mechanisms for these 4 units indicating different surface roughness properties. These multispectral and polarimetric SAR observations were combined with detailed surface textures and morphological features as visible in very high-resolution Quickbird imagery (61 cm/pixel). Remote sensing parameters and their thresholds for characterizing each unit were implemented into a decision-tree algorithm and a remote predictive geological map was produced. Subsequent field and follow-up laboratory investigations enabled the ground-truthing of these predictions. The geological units were defined as follows: (i) (smooth) fluvioglacial deposits, (ii) (moderately rough) chert-bearing dolostone, (iii) (rough) dolostone, and (iv) (rough) dolostone covered by silicified surfaces. The rough surfaces characterized by multiple scattering in the polarimetric SAR decomposition correspond to the occurrences of weathered carbonate rocks, which are relatively resistant to weathering and form blocky surfaces. This shows that SAR-derived surface roughness properties can greatly contribute to defining geological units by combining with lithological mapping. [ABSTRACT FROM AUTHOR]

Alvars are rare in Canada and uncommon globally. This study represents the first formal attempt to describe and delineate the extent of alvars in Manitoba. A systematic examination of the Interlake region's edaphic and biological characteristics, using a geographic information system, resulted in the identification of 67 sites warranting further field study. Of these sites, 61 were surveyed and information was collected on vegetation composition and structure, soil characteristics, land ownership, and land use. Alvar was confirmed at 28 sites, extending over approximately 3930 ha in five geographically distinct clusters. Four putative types of alvar communities are described: grassland, shrubland, savannah, and wetland. Livestock grazing is the dominant land use and occurs across more than three-quarters of Manitoba alvar. Approximately 12% coincide with mining claims or quarry leases. Two-thirds occur on publicly owned land. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In mature field appraisal and development, discretized geomechanical property models play a vital role in providing information on in situ stress regime as a guide for placement of directional wells. Laboratory methods of measuring these properties, in most cases, take only small samples from consolidated rocks. These isolated samples may not be representative of the entire elastic regime existing in the reservoir owing to sample size. In general, geomechanical studies are performed on a well-by-well basis and then these measurements are used as calibration points to convert 3D seismic data (if available) to geomechanical models. However, elastic properties measured this way are restricted to the well location and interpolation across the reservoir may not be always appropriate. To overcome these challenges, this paper describes an integrated approach for deriving 3D geomechanical models of the reservoir by combining results of 3D geocellular models and basin models. The basin model reconstructs the geologic history (i.e., burial history) of the reservoir by back-stripping it to the original depositional thickness. Through this reconstruction, the mechanical compaction, pore pressures, effective stress, and porosity versus depth relationships are established. Next, these mechanical properties are discretized into 3D geocellular grid using empirical formulas via lithofacies model even if no 3D seismic data are available for the reservoir. The discretization of elastic properties into 3D grids results in a better understanding of the prevailing stress regimes and helping in design of hydraulic fracturing operations with minimal risks and costs. This approach provides an innovative way of determining effective horizontal stress for the entire reservoir through 3D distribution of elastic properties. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The spatial distribution of soil shear-wave velocity and the fundamental period of vibration were selected as input parameters for the determination of potential seismic site effects in the Saguenay region, Canada. The methodology used in this study involved three clear steps. First, a 3D geological model of the surficial deposits was built taking into consideration the type, spatial distribution and thickness of the deposits. Second, representative averageVsvalues were determined for each of the major soil units. Finally, the average shear-wave velocity from the ground surface to bedrock (Vsav), the shear-wave velocity of the upper 30 m (Vs30) and the fundamental site resonance period (T0) were calculated over a regular grid for the study area. The results include the spatial distribution of the fundamental site resonance period, the average shear-wave velocity in the first 30 m of the ground and the spatial distribution of National Building Code of Canada seismic soil classes for the Saguenay region. [ABSTRACT FROM PUBLISHER]

The article features the Redpath Museum at the McGill University in Montreal, Quebec, and the minerals it preserved and showcased. It describes the function of the oldest purpose-built natural history museum in Canada. It discusses the history of the said museum which was built by industrialist Peter Redpath as a tribute to John William Dawson. It chronicles the museum's mineral collection dating back to the 1820s.

The Ottawa Embayment is an intracratonic rift basin in eastern North America that preserves a unique and eventful history through deep time. We report single-grain zircon and apatite (U-Th)/He and biotite 40Ar/39Ar data fromsamples collected along a 250-km transect across the crystalline rift flank and through the sedimentary sequences of the embayment. The data sets show significant intrasample age dispersions, and we investigate the influence of zircon crystallinity and nonideal crystal shapes on He diffusion through the application of Raman spectroscopy and X-ray microcomputed tomography. Ultimately, we utilize the relationship between radiation damage and heliumdiffusion to quantify observed age dispersion. We integrate our age data from the basement and overlying sedimentary unit of the embayment with regional geology to utilize multisample inverse modeling to reveal viable thermal histories that we then further evaluate by using the forwardmodelingmethod to improve our understanding of the thermal history of the rift system. Modeling of the thermochronometric data shows evidence of previously unrecognized reheating events in the embayment, including (1) during rifting and breakup of Rodinia in the late Neoproterozoic (ca. 750-590 Ma); (2) in the late Paleozoic, due to a combination of burial, an elevated geothermal gradient, and hydrothermal fluids, as associated with orogenic activity; and (3) maximum Mesozoic reheating to 150°C at 100 Ma, possibly related to passage of the Great Meteor hotspot or a major plate reorganization event. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The upper lower Cambrian Gog Group in the southern Rocky Mountains of Canada displays a high diversity and abundance of arthropod traces. Four ichnogenera,Cruziana, Diplichnites, Monomorphichnus, Rusophycus, and “Indeterminate Arthropod Scratches” are discussed, with a total of 17 different ichnospecies, as follows:Cruziana billingsiFillion and Pickerill, 1990,Cruziana irregularisFenton and Fenton, 1937,Cruziana jenningsiFenton and Fenton, 1937,Cruziana navicellaFenton and Fenton, 1937,Cruziana omanicaSeilacher, 1970,Cruziana pectinataSeilacher, 1994,Cruziana penicillataGibb, Chatterton, and Pemberton, 2009,Cruziana plicataCrimes, Legg, Marcos, and Arboleya, 1977,Cruziana tenellaLinnarsson, 1871,Diplichnites twelvetreesi(Chapman, 1928),Monomorphichnus bilinearisCrimes, 1970b,Monomorphichnus lineatusCrimes, Legg, Marcos, and Arboleya, 1977,Rusophycus eutendorfensis(Linck, 1942), andRusophycus unilobus(Seilacher, 1970). Three new ichnospecies, i.e.,Cruziana caputinclinataisp. nov.,Rusophycus subnotousisp. nov., andDiplichnites obliquusisp. nov., are proposed, described, and illustrated. The ichnofauna collected from three localities (Lake O'Hara, Mount Babel, and Redoubt Mountain) are predominantlyCruziana. Evidence of nutrient-rich substrates containing microbially induced sedimentary structures and the ichnospecies present confirm that the trace fossil bearing strata are part of theCruzianaichnofacies and were deposited in a fully marine basin between fair weather wave base and storm wave base. [ABSTRACT FROM PUBLISHER]

ABSTRACT Current models for unconformity-associated uranium deposits predict fluid flow and ore deposition along reactivated faults in >1.76 Ga basement beneath Mesoproterozoic siliciclastic basins. In frontier regions such as the Thelon Basin in the Kivalliq region of Nunavut, little is known about the sub-basin distribution of units and structures, making exploration targeting very tenuous. We constructed a geological map of the basement beneath the unconformity by extrapolating exposed features into the subsurface. The new map is constrained by detailed geological, geophysical, and rock property observations of outcrops adjacent to the basin and by aeromagnetic and gravity data over the geophysically transparent sedimentary basin. From rock property measurements, it is clear that the diverse magnetic and density characteristics of major rock packages provide quantitative three-dimensional constraints. Gravity profiles forward modelled in four cross sections define broad synforms of the Amer Belt and Archean volcanic rocks that are consistent with the structural style outside the basin. Major lithotectonic entities beneath the unconformity include: supracrustal rocks of the Archean Woodburn Lake group and Marjorie Hills meta sedimentary gneiss and associated mixed granitoid and amphibolitic gneiss; the Amer Mylonite Zone and inferred mafic intrusions oriented parallel and sub-parallel; other igneous intrusions of 2.6 Ga, 1.83 Ga, and 1.75 Ga vintage; and the <2.3 Ga to >1.84 Ga Amer Group. Four main brittle regional fault arrays (040°-060°, 075°-90°, 120°, and 150°) controlled development and preservation of the basin. The reactivated intersections of such faults along fertile basement units such as the Rumble assemblage, Marjorie Hills assemblage, Nueltin igneous rocks, and Pitz formation are the best targets for uranium exploration. [ABSTRACT FROM AUTHOR]

The installation cost and the performance of geothermal heat pump systems are influenced by the thermal state and properties of the subsurface. The ground ability to transfer heat described by thermal conductivity is a dominant factor affecting the favorability of closed-loop ground heat exchangers installed in vertical boreholes. A study that aimed at evaluating the geothermal heat pump potential by mapping the thermal conductivity of rock sequences was, therefore, performed for the St. Lawrence Lowlands sedimentary basin in Canada. Thermal conductivity was measured in the laboratory on rock samples collected in outcrops and used to complete design calculations of a geothermal system with a single borehole. Results allowed the definition of thermostratigraphic units that can be linked to depositional environments. Basal quartz-rich sandstones formed in a rift environment show a high geothermal potential. Overlying dolomites, argillaceous limestones and shales deposited in a passive margin evolving to a foreland basin exhibit a transition toward the top from high to low geothermal potential. Upper turbidites and molasses have a moderate geothermal potential. The thermal conductivity of the thermostratigraphic units is dominantly influenced by the mineralogy of the sedimentary rocks. Understanding their origin is a key to improve geothermal resource assessment and system design to anticipate new installations in the area. [ABSTRACT FROM AUTHOR]

Assimilation by mafic to ultramafic magmas of sulfur-bearing country rocks is considered an important contributing factor to reach sulfide saturation and form magmatic Ni-Cu-platinum group element (PGE) sulfide deposits. Sulfur-bearing sedimentary rocks in the Archean are generally characterized by mass-independent fractionation of sulfur isotopes that is a result of atmospheric photochemical reactions, which produces isotopically distinct pools of sulfur. Likewise, low-temperature processing of iron, through biological and abiotic redox cycling, produces a range of Fe isotope values in Archean sedimentary rocks that is distinct from the range of the mantle and magmatic Fe isotope values. Both of these signals can be used to identify potential country rock assimilants and their contribution to magmatic sulfide deposits. We use multiple S and Fe isotopes to characterize the composition of the potential iron and sulfur sources for the sulfide liquids that formed the Hart deposit in the Shaw Dome area within the Abitibi greenstone belt in Ontario (Canada). The Hart deposit is composed of two zones with komatiite-associated Ni-Cu-PGE mineralization; the main zone consists of a massive sulfide deposit at the base of the basal flow in the komatiite sequence, whereas the eastern extension consists of a semi-massive sulfide zone located 12 to 25 m above the base of the second flow in the komatiite sequence. Low δFe values and non-zero δS and ΔS values of the komatiitic rocks and associated mineralization at the Hart deposit is best explained by mixing and isotope exchange with crustal materials, such as exhalite and graphitic argillite, rather than intrinsic fractionation within the komatiite. This approach allows tracing the extent of crustal contamination away from the deposit and the degree of mixing between the sulfide and komatiite melts. The exhalite and graphitic argillite were the dominant contaminants for the main zone of mineralization and the eastern extension zone of the Hart deposit, respectively. Critically, the extent of contamination, as revealed by multiple S and Fe isotope systematics, is greatest within the deposit and decreases away from it within the komatiite flow. This pattern points to a local source of crustal contamination for the mantle-derived komatiitic melt and a low degree of homogenization between the mineralization and the surrounding lava flow. Coupled S and Fe isotope patterns like those identified at the Hart deposit may provide a useful tool for assessing the potential of a komatiitic sequence to host Ni-Cu-(PGE). [ABSTRACT FROM AUTHOR]

In this study we examined Meso- to Neoarchean granitoids from the North Caribou Terrane within the Western Superior Province, Canada. Petrology, whole-rock geochemistry, zircon and titanite geochronology, and zircon trace element concentrations were analyzed. U-Pb ages from zircon and titanite are between 262 and 313 Ga. Although most of the granitoids in this study appear to record a complex magmatic history, about a third contain features that we interpret to be a result of hydrothermal alteration. Notable traits in rocks that contain altered zircons include K-feldspar overgrowths on plagioclase and compositional zoning in titanite. The altered zircon material itself occurs as CL-bright resorption shadows showing distinct chemical changes, including lower Th/U values and elevated LREE concentrations. The isotopic ages of the rims on the altered zircons (2835 Ma, 2760-2678 Ma) are similar to coexisting U-Pb titanite ages and regional U-Pb titanite and zircon ages. We propose that during the hydrothermal event, the affected areas of zircon reequilibrated with fluid, which promoted Pb loss, resetting the isotopic clock. These results suggest that zircon rims might be useful for dating hydrothermal fluid flow episodes in addition to magmatic events and that a multi-element approach is useful for distinguishing ages that are magmatic from those that have been isotopically disturbed owing to alteration. [ABSTRACT FROM AUTHOR]

Presents comments on a study concerning the role of bentonite in a case of secondary thickening in a late Campanian volcanic ash fall in central Alberta. Purpose of plotting the logarithm of isopach thickness against the square-root of the isopach area; Occurrence of exponential thickness decay.

Nymphaea loriana Wiersema, Hellq. & Borsch (Lori's Water-lily) is a newly described, Canadian endemic species that has been found in central Manitoba and east-central Saskatchewan. To assess the status of a species, data regarding its distribution, population size, habitat, and search effort are needed. The purpose of this paper is to document these factors for this species. The extent of occurrence of N. loriana is approximately 15 100 km2 but the known area of occupancy is a mere 20 km2. The estimated population size of N. loriana is about 750 individual plants, although more may exist on poorly explored rivers and lakes within the extent of occurrence and possibly in northeastern Ontario. Nymphaea loriana occurs in fresh, stagnant, or slowly moving water in boreal lakes and rivers and is typically associated with N. leibergii (Dwarf Water-lily), Schoenoplectus tabemaemontani (Soft-stemmed Bulrush), Potamogeton natans (Floating-leaved Pondweed) and Nuphar variegata (Variegated Pondlily). Potential threats to the persistence of this species include low water quality resulting from mining, forestry, and agriculture, and changes to water flow because of dam construction and climate change. Monitoring known populations and searching for additional ones may be needed to assess the status of this species. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)