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The Erie Interstade is generally accepted to have been a relatively warm period associated with retreat of the Laurentian ice sheet into the Lake Ontario basin, followed by a readvance to the Valley Heads (Port Bruce Stade) ice front in central New York. Recent investigations in the Cayuga basin indicate that this ice front retreated only to the Ithaca area during the Erie Interstade. In the Cayuga trough, Erie glaciolacustrine strata underlie Valley Heads deposits. Plant assemblages in these strata indicate a sub-Arctic environment. Erie deposits also occur in the Fall Creek Valley, where a varved sequence below Valley Heads till and above Nissouri till indicate deposition close to a retreating ice front. Remanent magnetic declination in the varves is 357[degrees], best correlated with lower Newport beds of the Middleville fm in the Mohawk Valley and suggests an age of 17.7 [+ or -] 0.1 kacal for the peak of the Erie retreat. Retreat only to the Ithaca area is based on the lack of Erie deposits north of Ithaca, an oscillation of the ice front around the south end of Cayuga Lake, and the lack of a fluvial interval in the Cayuga trough that would have marked retreat into the Ontario basin. Ice core data from Greenland and sea level studies demonstrate that the Erie Interstade was neither a warm period nor a time of significant sea level rise. The Erie Interstade retreat/Valley Heads readvance appears instead to represent a minor reversal in the general, slow ice front retreat from the Last Glacial Maximum to the warm up at Melt Water Pulse 1. Key words: Erie Interstade, central New York, deglacial geology, Cayuga basin, Introduction The Erie Interstade was defined by Dreimanis (1958), based on exposures north of Lake Erie, and was extensively described by Morner and Dreimanis (1973) as a relatively warm period [...]

The Mesnard Quartzite of Paleoproterozoic age is believed to represent among the first preserved cratonal continental rocks in the Lake Superior region, was deposited above Archean basement in the Marquette structural trough and is estimated to contain more than 99% sandstone (now quartzite) beds. The Mesnard Quartzite is interpreted to have been deposited largely by tidal currents. Evidence of tidal current deposition includes lack of wave-influenced structures such as hummocky cross-beds, and presence of strongly unidirectional paleocurrents from cross-beds, mud-drapes on cross-bed foresets, evidence of current reversal including herringbone cross-bedding and sigmoidal cross-bedding. Sandstone bedding types include homogeneous or structureless beds, parallel-laminated beds, cross-beds, and symmetric ripple marks. Unidirectional paleocurrents from cross-beds are largely subparallel to the axis of the Marquette structural trough, leading to the interpretation that the trough was subsiding during deposition. Cross-bed set thickness and symmetric ripple marks both support the interpretation of shallow water marine deposition, likely only a few meters. Although the Mesnard Quartzite is on the order of 110 m thick, there is no evidence of internal sequence boundaries or flooding surfaces, and low accommodation during deposition is inferred. The climate during deposition is interpreted to be humid, and tropical to subtropical based on the quartz arenite composition. Deposition likely occurred in a failed rift basin or in an intracratonic extensional basin. Key words: tidal, sequence stratigraphy, sedimentology, depositional environments, Paleoproterozoic, Lake Superior, Introduction The Mesnard Quartzite is the basal sandstone interval in the Paleoproterozoic Chocolay Group of the Marquette Range Supergroup in northern Michigan (Cannon and Gair 1970; Cannon 1973). The Chocolay [...]

Over 50 years ago, a marine estuary was converted to a wastewater stabilization basin for treatment of primarily pulp and paper effluent. As a result, the basin was immediately converted to a 'freshwater' environment and subsequently accumulated a thin layer of black, organic-rich sediment containing varying amounts of dioxins and furans, metals, polycyclic aromatic hydrocarbons, and petroleum hydrocarbons. Previous studies on the site have shown that the majority of this contamination in the basin appears to have been contained within this black sediment layer and not migrated to any significant extent into the original underlying marine sediments. The purpose of this study is to examine sediment porewater chemistry changes that have occurred over 51 years of operation of the stabilization basin with the intent of better understanding why contamination has been minimal into the underlying natural marine sediments. Field and laboratory testing is presented to characterize the physical, chemical, and mineralogical sediments in the basin. Porewater chemistry profiles obtained from this work are then used in combination with a one-dimensional contaminant transport model to examine the role of diffusion, sorption, and upward groundwater flux in the porewater profiles found for the sediments. Key words: contaminant migration, diffusion, sorption, barrier, pulp and paper Il y a plus de 50 ans, un estuaire marin a ete converti en bassin de stabilisation des eaux usees pour le traitement d'effluents principalement issus du secteur de la pate a papier. En consequence, le bassin a ete immediatement converti en un environnement << d'eau douce >> et a ensuite accumule une fine couche de sediments noirs, riches en matieres organiques, contenant des quantites variables de dioxines et de furanes, de metaux, d'hydrocarbures aromatiques polycycliques et d'hydrocarbures petroliers. Des etudes anterieures sur le site ont montre que la majorite de cette contamination dans le bassin semble avoir ete contenue dans cette couche de sediments noirs et n'a pas migre de maniere significative dans les sediments marins sousjacents originaux. Le but de cette etude est d'examiner les changements de la chimie de l'eau interstitielle des sediments qui se sont produits au cours des 51 annees d'exploitation du bassin de stabilisation dans l'intention de mieux comprendre pourquoi la contamination a ete minimale dans les sediments marins naturels sous-jacents. Des essais sur le terrain et en laboratoire sont presentes pour caracteriser les sediments physiques, chimiques et mineralogiques du bassin. Les profils chimiques des eaux interstitielles obtenus a partir de ce travail sont ensuite utilises en combinaison avec un modele unidimensionnel de transport des contaminants pour examiner le role de la diffusion, de la sorption et du flux ascendant des eaux souterraines dans les profils des eaux interstitielles trouves pour les sediments. [Traduit par la Redaction] Mots-cles : migration des contaminants, diffusion, sorption, barriere, pate et papier, 1. Introduction Boat Harbour (BH) is the stabilization basin, which until 2020, comprised part of a wastewater treatment facility located near Pictou, Nova Scotia, Canada. A tidal estuary until 1967, [...]

Context. Cropping in the Queensland Murray-Darling and Fitzroy Basins has precursors for secondary salinity--high soil salt loads and increased drainage after clearing. Aims. To measure changes in deep drainage, for key tillage, traffic, and cropping systems. Methods. Steady-state and transient chloride (CI) mass-balance were applied to Cl profiles from four tillage and crop rotation trials and one controlled traffic trial in southern and central Queensland, to determine deep drainage below the root zone. Key results. Large downward movement of Cl occurred after clearing. Deep drainage from transient Cl balance for cropping was a small proportion of rainfall but considerably higher than under native vegetation. Deep drainage was consistently greater under zero than conventional tillage, for both winter and summer cropping. For example, deep drainage was greatest for zero tillage (~45 mm/year) and least for conventional, stubble mulch, and reduced tillage (2-6.3 mm/year) at the highest-rainfall site (677 mm/year). Deep drainage was 12.7 and 7.9 mm/year for zero and conventional tillage, respectively, at the lowest-rainfall site (497 mm/year). Drainage under continuous wheat conventional tillage was more than twice that where some summer crops were included. At Billa Billa, continuous wheat had greater deep drainage by three to five times than continuous sorghum for three of four tillage systems. No drainage was detected during 6 years of opportunity cropping. A pasture legume ley had only 1.7 mm/year of deep drainage. Deep drainage was less for compacted than non-compacted treatments (23.3 vs 38.2 mm/year). Conclusion and implications. Increased deep drainage with zero tillage and controlled traffic can be reduced using summer crops, particularly opportunity cropping where crops are planted when soil water is sufficient, and ley pastures. Keywords: compaction, cracking clay, dryland salinity, native vegetation, opportunity cropping, steady-state mass-balance, transient mass-balance, Vertosols., Introduction The importance of deep drainage under different land uses, and its relationship to salinity risk has been studied extensively in the dryland cropping areas of inland Queensland (Qld), Australia, [...]

Sputnik Planitia is a nitrogen-ice-filled basin on Pluto.sup.1. Its polygonal surface patterns.sup.2 have been previously explained as a result of solid-state convection with either an imposed heat flow.sup.3 or a temperature difference within the 10-km-thick ice layer.sup.4. Neither explanation is satisfactory, because they do not exhibit surface topography with the observed pattern: flat polygons delimited by narrow troughs.sup.5. Internal heating produces the observed patterns.sup.6, but the heating source in such a setup remains enigmatic. Here we report the results of modelling the effects of sublimation at the surface. We find that sublimation-driven convection readily produces the observed polygonal structures if we assume a smaller heat flux (~0.3 mW m.sup.-2) at the base of the ice layer than the commonly accepted value of 2-3 mW m.sup.-2 (ref. .sup.7). Sustaining this regime with the latter value is also possible, but would require a stronger viscosity contrast (~3,000) than the nominal value (~100) considered in this study. A modelling study describing the formation of the polygonal surface structures in Sputnik Planitia on Pluto shows that convection driven by ice sublimation can generate planetary-scale surface patterns., Author(s): Adrien Morison [sup.1] , Stéphane Labrosse [sup.2] , Gaël Choblet [sup.3] Author Affiliations: (1) Physics and Astronomy, University of Exeter, Exeter, UK (2) LGL-TPE, Université de Lyon, ENSL, Univ [...]

A new three-dimensional (3D) inversion strategy is applied to new compilations of gravity and magnetic data to reassess the role of crustal lineaments in the development of the western Laurentian margin, Selwyn Basin, and associated sediment-hosted zinc-lead (Zn-Pb) deposits. The region's history is obscured by multiple tectonic overprints, including terrane accretion, plutonism, and thrust faulting. Regionally continuous, broadly northeast-trending crustal lineaments, including the Liard line, Fort Norman structure, and Leith Ridge fault, were interpreted as having had long-standing influence on craton, margin, and sedimentary basin development. An east-northeast-trending lineament, Mackenzie River, traced from the Misty Creek Embayment to Great Bear Lake, is interpreted as the southern edge of a cratonic promontory. The location of the Liard line, associated with a transfer fault that bounds the Macdonald Platform promontory, is refined. New geophysical results support the continuity of the Fort Norman structure below the Selwyn Basin, but limited evidence exists for the Leith Ridge fault in this area. A northwest-trending lineament that bounds the craton is interpreted as a crustal manifestation of litho-spheric thinning of the Laurentian margin, as echoed by a change in the depth of the lithosphere-asthenosphere boundary. The structure delimits the eastern extent of mid-to Late Cretaceous granitic intrusions and is straddled by Mississippi Valley-type Zn-Pb occurrences, following their palinspastic restoration. Clastic-dominated Zn-Pb occurrences are aligned along another northwest-trending lineament interpreted to be associated with a shallowing of lower crustal rocks. Key words: Canadian Cordillera, gravity, Laurentia, Selwyn Basin, sediment-hosted Zn-Pb deposits. Une nouvelle strategie d'inversion tridimensionnelle (3D) est appliquee a de nouvelles compilations de donnees gravi-metriques et aeromagnetiques afin de reevaluer le role de lineaments crustaux dans le developpement de la marge laurentienne occidentale, du bassin de Selwyn et de la mineralisation en zinc-plomb (Zn-Pb) associee dans des sediments. L'histoire de la region est masquee par de multiples episodes tectoniques surimposes comprenant l'accretion de terranes, du plutonisme et la formation de failles de chevauchement. Des lineaments crustaux regionaux continus, generalement d'orientation nord-est, dont la ligne de Liard, la structure de Fort Norman et la faille de Leith Ridge, ont ete interpretes comme ayant eu une influence prolon-gee sur le developpement du craton, de la marge et du bassin sedimentaire connexe. Un lineament d'orientation est-nord-est, du fleuve Mackenzie, observe depuis l'echancrure de Misty Creek jusqu'au Grand lac de l'Ours, est interprete comme marquant la bordure sud d'un promontoire cratonique. L'emplacement de la ligne de Liard, associee a une faille de transfert qui delimite le promontoire de la plateforme de Macdonald, est precise. De nouveaux resultats geophysiques soutiennent l'interpretation de la continuite de la structure de Fort Norman sous le bassin de Selwyn, mais les observations concernant la faille de Leith Ridge sont limitees dans cette region. Un lineament d'orientation nord-ouest qui borde le craton est interprete comme etant une manifestation crustale de l'amincissement lithospherique de la marge laurentienne, comme en temoigne un changement de la profondeur de la limite lithosphere-asthenosphere. La structure delimite l'etendue vers l'est d'intrusions granitiques du Cretace tardif et est surmontee par des indices de Zn-Pb de type Mississippi Valley, apres leur reconstitution palinspatique. Les indices de Zn-Pb a dominante clastique sont alignes le long d'un autre lineament d'orientation nord-ouest interprete etre associe a une diminution de la profondeur des roches de la croute inferieure. [Traduit par la Redaction] Mots-cles: Cordillere canadienne, gravite, Laurentie, bassin de Selwyn, gites de Zn-Pb dans desrochessedimentaires., Introduction The tectonic history of the western margin of the North American craton (Laurentia) in northwestern Canada suggests that it formed from the progressive accretion of 2.3-1.8 Ga magmatic arcs [...]

Based on the study of cores, thin sections, and outcrops, the sedimentary facies of the lower Cambrian carbonate rocks in the northern Tarim Basin can be divided into four types: restricted platform, open platform, ramp, and basin. Based on the lithologic analysis of thin sections, two-dimensional seismic data interpretation, and an isopach map of the lower Cambrian Xiaoerbulake Formation in the study area, seven sedimentary facies of carbonate rocks were identified, including inner platform depression, shoal, intershoal sea, platform margin, gypsum salt lake, ramp, and basin. The depositional model of the lower Cambrian Xiaoerbulake Formation in the northern Tarim Basin is constructed based on this integrated research. The topset, foreset, and bottomset of oblique progradational reflections are interpreted as the platform margin beach, ramp, and basin environments, respectively. The thicker area with micritic dolomite as the dominant lithology is interpreted as a platform depression. The low-amplitude hummocky reflections are interpreted as shoals that consist of a variety of granular dolomite and algal dolomite. The thinner uplifted area with gypsum and dolomite present in cores is interpreted as a restricted platform with a gypsiferous dolomite tidal flat or lake environment. Well LT1, which was drilled recently in the platform margin and ramp region, as indicated by seismic progradational clinoform reflections, has produced high yields of oil and gas. Supported by the above research results, the map of the lithofacies and paleogeography of the Xiaoerbulake Formation in the northern Tarim Basin was recompiled. Key words: Tarim Basin, lower Cambrian, Xiaoerbulake Formation, lithofacies and paleogeography, seismic facies. A la lumiere de l'etude de carottes, de lames minces et d'affleurements, les facies sedimentaires des roches carbonatees du Cambrien inferieur dans le nord du bassin de Tarim peuvent etre subdivises en quatre types, a savoir, les facies de plateforme restreinte, de plateforme ouverte, de talus et de bassin. A la lumiere de l'analyse lithologique de lames minces, de l'interpretation de donnees de sismique bidimensionnelle et d'une carte d'isopaques de la Formation de Xiaoerbulake du Cambrien inferieur dans la region a l'etude, sept facies sedimentaires de roches carbonatees ont ete etablis, soit les facies de depression de plateforme interne, de basse, de mer inter-basse, de marge de plateforme, de lac de sel de gypse, de talus et de bassin. Le modele de depot de la Formation de Xiaoerbulake dans le nord du bassin de Tarim est etabli sur la base de cette recherche integree. La couche sommitale, la couche frontale et la couche basale des reflexions progradantes obliques sont interpretees comme etant les milieux de plage de marge de plateforme, de talus et de bassins, respectivement. La zone plus epaisse dans laquelle de la dolomie micritique constitue l'unite dominante est interpretee comme representant une depression de plateforme. Les reflexions bosselees de faible amplitude sont interpretees comme etant des basses constituees variablement de dolomie granulaire et de dolomie algale. La zone soulevee plus mince dont les carottes contiennent du gypse et de la dolomie est interpretee comme etant une plateforme restreinte caracterisee par un milieu de platin ou de lac a dolomie gypsifere. Le puits LT1 fore recemment dans la region de marge de plateforme et de talus, comme l'indiquent les reflexions clinoformes progradantes, a produit de bons rendements petroliers et gaziers. La carte des lithofacies et de la paleogeographie de la Formation de Xiaoerbulake dans le bassin de Tarim a ete recompilee a la lumiere des resultats de recherche susmentionnes. [Traduit par la Redaction] Mots-cles : bassin de Tarim, Cambrien inferieur, Formation de Xiaoerbulake, lithofacies et paleogeographie, facies sismique., Introduction The Cambrian dolomitic rocks in the Tarim Basin have a thickness of more than 1 km and a distribution area of 410 000 [km.sup.2] (Du and Pan 2016). In [...]

The McAra deposit is in eastern Ontario, Canada, and is hosted in an Archean inlier to the Paleoproterozoic Huronian basin. It is currently estimated to contain ~2.4 million pounds of cobalt at an average grade of 1.25%. New drill data show the mineralized zone comprises glaucodot-cobaltite veins and breccias that transect a mafic-siliciclastic volcanogenic massive sulfide (VMS) deposit. The high cobalt grade and host stratigraphy at the McAra deposit contrast with five-element (Ag-Co-Ni-Bi-As) deposits at the Cobalt and Gowganda camps in the region that produced high-grade silver and by-product cobalt from veins spatially associated with Nipissing Gabbro intrusions. However, geochemical data from recent core samples alongside fluid inclusion and mineralogical data suggest the cobalt zone at McAra and the five-element veins share a similar metal assemblage and were deposited from similar fluids. The mafic-siliciclastic VMS deposit at McAra contains anomalous amounts of cobalt, suggesting the Archean host stratigraphy was the source for the high-grade cobalt zone. Basin brines in the Paleoproterozoic are interpreted to have leached cobalt from Archean rocks and then redeposited it through oxidation-reduction reactions along synvolcanic faults that controlled earlier VMS deposit formation. High-resolution aeromagnetic data show that McAra is immediately adjacent to a mafic dike that transects the Huronian basin along a northwest-striking, crustal-scale fault system. These data, alongside observations from field mapping, also suggest the deposit is on the margin of a sub-basin that contains an 80 [km.sup.2] Nipissing sill that may have originally overlain the deposit area and been a hydrologic seal during mineralization. The new deposit- and regional-scale data and interpretations are used to create a model for the McAra deposit and provide evidence for why it is cobalt-rich relative to other five-element veins. The model and data can be used to guide exploration for additional cobalt-rich deposits in the region and similar settings globally. Key words: Paleoproterozoic Huronian basin, mineral exploration, VMS deposit, Neoarchean Wawa-Abitibi, cobalt deposit, magnetic and gravity data. Le gisement de McAra de l'est de l'Ontario (Canada) est encaisse dans une enclave archeenne du bassin paleoproterozoique huronien. Il est presentement estime qu'il contiendrait quelque 2,4 millions de livres de cobalt a une teneur moyenne de 1,25 %. De nouvelles donnees de forage montrent que la zone mineralisee comprend des filons et breches de glaucodot-cobaltite qui recoupent un gisement mafique-silicoclastique de sulfures massifs volcanogenes (SMV). La forte teneur en cobalt et la stratigraphie de la roche encaissante du gisement de McAra different de celles des gisements de cinq elements (Ag-Co-Ni-Bi-As) des camps de Cobalt et Gowganda dans la region qui on produit de l'argent de forte teneur et du cobalt accessoire provenant de filons associes dans l'espace a des intrusions de gabbro de Nipissing. Des donnees geochimiques d'echantillons de carottes recents, ainsi que des donnees mineralogiques et sur les inclusions fluides indiqueraient toutefois que la zone cobaltifere a McAra et les filons de cinq elements presentent des assemblages de metaux semblables et ont ete deposes par des fluides similaires. Le gisement de SMV mafique-silicoclastique de McAra contient des quantites anomaliques de cobalt, ce qui indiquerait que la stratigraphie des roches encaissantes archeennes est la source de la zone a fortes teneurs de cobalt. Il est interprete que, au Paleoproterozoique, des saumures du bassin ont lixivie du cobalt de roches archeennes pour ensuite le deposer par des reactions d'oxydoreduction le long de failles synvolcaniques qui avaient controle la formation anterieure de gisements de SMV. Des donnees aeromagnetiques de haute resolution montrent que le gisement de McAra est immediatement attenant a un dyke mafique qui recoupe le bassin huronien le long d'un systeme de failles d'envergure crustale de direction nord-ouest. Ces donnees, combinees a des observations de cartographie de terrain, donnent aussi a penser que le gisement se trouve a la bordure d'un sous-bassin contenant un filon-couche de gabbro de Nipissing de 80 [km.sup.2] qui pourrait avoir ete, au depart, au-dessus du secteur du gisement et avoir servi de couche impermeable aux fluides aqueux durant la mineralisation. Les nouvelles donnees et interpretations a l'echelle regionale et du gisement sont utilisees pour creer un modele pour le gisement de McAra et mettent en lumiere les raisons pour lesquelles ce gisement est relativement riche en cobalt comparativement a d'autres filons a cinq elements. Le modele et les donnees peuvent etre utilises pour guider l'exploration pour de nouveaux gisements riches en cobalt dans la region et dans des milieux semblables ailleurs dans le monde. [Traduit par la Redaction] Mots-cles: bassin paleoproterozoique huronien, exploration minerale, gisement SMV, ceinture neoarcheenne de Wawa-Abitibi, gisement de cobalt, donnees magnetiques et gravimetriques., Introduction The McAra cobalt deposit is ~150 km northeast of Sudbury, Ontario, and is hosted in an Archean inlier to the Paleoproterozoic Huronian basin (Figs. 1, 2). It is currently [...]

The Maritimes Basin of Atlantic Canada contains a rich record of Pennsylvanian cyclothems. Previous studies have focused on rapidly subsiding depocenters in the central part of the basin where Carboniferous successions feature cyclic alternations between terrestrial and marginal marine strata. In contrast, the Pennsylvanian Clifton Formation was deposited on the relatively stable New Brunswick platform and contains almost entirely terrestrial strata. Although early studies of the Clifton Formation noted a cyclic architecture, particularly within Member B, this unit has remained understudied. We provide a sedimentological and sequence stratigraphic framework for the lower 85 m of Member B and interpret our results relative to a broader regional framework. Near the base of the study interval, the highstand systems tract is composed of red floodplain mudrocks; overlying sequence boundaries are composed of calcretes and (or) channels. The transgressive systems tract and maximumflooding surface are representedby coals and aquatic bivalve-bearing mudrocks. Moving upward through the section, the architecture of the highstand systems tract remains largely unchanged while sequence-bounding paleosols become less well developed, the transgressive systems tract becomes thinner and eventually not preserved, and the maximum flooding surface is only occasionally preserved, possibly represented by carbonaceous shales. These changes in cyclic architecture may be attributed to changes in the magnitude of glacioeustatic fluctuations, climate, and (or) the accommodation/sediment supply ratio. The results of this study show that the Clifton Formation represents the terrestrial/proximal endmember for cyclicity in the Maritimes Basin and provide new insight into paleotopography as a possible control on cyclothem architecture. Key words: sequence stratigraphy, sedimentology, cyclicity, Clifton Formation, Maritimes Basin. Le bassin des Maritimes du Canada atlantique contient un riche registre de cyclothèmes pennsylvaniens. Les études antérieures se sont concentrées sur des centres de dépôt à subsidence rapide dans la partie centrale du bassin, où des successions carbonifères présentent des alternances cycliques de strates terrestres et de la marge océanique. En revanche, la Formation pennsylvanienne de Clifton a été déposée sur la plateforme relativement stable du Nouveau-Brunswick et est composée presque exclusivement de strates terrestres. Bien que des études antérieures de la Formation de Clifton aient noté une architecture cyclique, particulièrement dans son membre B, cette unité demeure sous-étudiée. Nous présentons un cadre sédimentologique et de stratigraphie séquentielle pour les 85 m inférieurs du membre B et interprétons nos résultats par rapport à un cadre régional plus large. Près de la base de l'intervalle étudié, un cortège de haut niveau est composé de mudrocks rouges de plaine inondable; les limites de séquence sus-jacentes sont composées de calcrètes ou de dépôts de chenaux. Le cortège transgressif et la surface d'inondation maximale sont représentés par des charbons et des mudrocks à bivalves aquatiques. Plus haut dans la coupe, l'architecture du cortège de haut niveau demeure largement inchangée, alors que les paléosols définissant des limites de séquence deviennent moins bien développés, le cortège transgressif devient plus mince, jusqu'à n'être plus préservé, et la surface d'inondation maximale n'est qu'occasionnellement préservée et possiblement représentée par des schistes charbonneux. Ces variations de l'architecture cyclique peuvent être attribuées à des variations de la magnitude des fluctuations glacioeustatiques, du climat ou du rapport entre l'espace disponible et l'apport de sédiments. Les résultats de l'étude montrent que la Formation de Clifton représente le membre de l'extrémité terrestre/proximale en ce qui concerne la cyclicité dans le bassin des Maritimeset fournit de nouveaux renseignements sur la paléotopographie comme contrôle possible de l'architecture des cyclothèmes. [Traduit par la Rédaction] Mots-clés : stratigraphie séquentielle, sédimentologie, cyclicité, Formation de Clifton, bassin des Maritimes., Introduction Cyclothems are cyclic, often coal-bearing successions of marine and (or) terrestrial strata typical of late Paleozoic sedimentary basins (e.g., Udden 1912; Wanless and Shepard 1936; Heckel et al. 1998). [...]

During the spring of 2018, residents Gary, David, and Rick Leblanc, found a near-horizontal burrow fossil within red sandstone along a ditch outcrop at Midland, New Brunswick. These red sandstones, [...]

Newly discovered tetrapod and invertebrate ichnofossils from the Pennsylvanian (Westphalian C) Stellarton Formation represent the first ichnofossil assemblage to be described in the Stellarton Basin of Nova Scotia. The Stellarton [...]

More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basins floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers., Author(s): Edgardo M. Latrubesse (corresponding author) [1, 2]; Eugenio Y. Arima [1]; Thomas Dunne [3]; Edward Park [1]; Victor R. Baker [4]; Fernando M. dHorta [5]; Charles Wight [1]; Florian [...]

The Visean-Serpukhovian transition in Atlantic Canada was marked by a general humidification of the climate as the region drifted towards equatorial latitudes. It also corresponds to a time when ice volume was increasing on Gondwana, which marked the end of Mississippian marine incursions in the region. Glacioeustatic fluctuations of greater magnitude are thought to have increased the response of the regional climate to third-order cyclicity from orbital forcing. In the Cumberland Basin, fluvial grey beds of the lower Serpukhovian Shepody Formation were deposited in sub-humid conditions during highstands, whereas red playa deposits of the same unit were deposited under semi-arid conditions during lowstands. Basin reconstruction suggests that this unit was sourced from the fault-bounded Cobequid and Caledonia highlands and deposited in two separate salt-withdrawal minibasins. This fluvial system was seemingly discharging to the north into the broad lake that deposited the contemporaneous Hastings Formation. A disconformity separates the Shepody Formation from mid-Serpukhovian red beds of the Claremont Formation and is tentatively associated with another increase in ice volume on Gondwana followed by a recrudescence of fault activity and basin subsidence. A prolonged time of aridity, floral crisis, non-deposition, deep weathering and karstification in late Serpukhovian to early Bashkirian times is contemporaneous with abundant glacial deposits in higher latitudes, suggesting that globally low sea levels may have been at play in creating a situation of greater continentality in the study area. La transition du Viseen au Serpukhovien dans le Canada atlantique fut marquee par une humidification generale du climat alors que la region derivait en direction des latitudes equatoriales. Cette epoque correspond a un temps durant lequel le volume des glaces etait croissant sur Gondwana, mettant ainsi fin aux incursions marines mississippiennes dans la region. L'amplitude croissante des fluctuations glacioeustatiques a l'epoque aurait rendu le climat regional plus sensible aux cycles orbitaux de troisieme ordre. Dans le bassin de Cumberland, les lits fluviaux gris de la formation de Shepody (Serpukhovien inferieur) se seraient deposes dans des conditions sub-humides durant des temps de hauts niveaux marins, tandis que les depots de playa de la meme unite se seraient deposes dans des condition semi-arides durant des temps de bas niveaux marins. Cette unite se serait deposee a partir des hautes-terres de Cobequid et de Caledonia a l'interieur de deux mini-bassins distincts. Ce systeme fluviatile aurait connecte au nord a un grand lac dans lequel se serait deposee la formation contemporaine de Hastings. Une discordance d'erosion separe la formation de Shepody des lits rouges de la formation de Claremont (Serpukhovien moyen) et corresponderait a une autre recrudescence des glaces sur Gondwana suivie par une augmentation des taux de subsidence et d'activite de failles. Des temps prolonges d'aridite, de crise florale, de non-deposition, d'alteration profonde et de karstification durant le Serpukhovien superieur et le Bashkirien inferieur sont contemporains a des depots glaciaires abondants en hautes latitudes, suggerant qu'un bas niveau marin global aurait pu aggraver les conditions de continentalite dans la region etudiee., Introduction In early Visean times, the composite Maritimes Basin of eastern Canada (Fig. 1; inset) accommodated an approximately 1 km thick succession of evaporites in many of its subbasins, including [...]

During the Carboniferous, the assembly of the supercontinent Pangea periodically reactivated strike-slip faults and shear zones that transect the northern Appalachian orogen. These strike-slip deformation zones represent crustal-scale tectonic boundaries [...]

The Maritimes Basin of Atlantic Canada is a large and deep sedimentary basin underlying large parts of Atlantic Canada. The basin fill is predominantly late Paleozoic (Devonian--Permian) non-marine clastic sedimentary [...]

The Bay St. George subbasin of SW Newfoundland, part of the larger late Paleozoic Maritimes basin, formed under the influence of strike-slip faulting and the movement of evaporites. New stratigraphic [...]

The Maritimes Basin is composed of multiple intra-basin depocentres each with variable structural and depositional regimes related to halokinesis. The Cumberland Basin, in northwestern Nova Scotia, is one such depocentre [...]

Recent integration of seismic profiles, palynology, industry reports, boreholes, and field interpretation has confirmed the existence of the Millstream Subbasin, an approximately 80 k[m.sup.(2) pull-apart basin within the Midland area [...]

The Grande Anse Formation crops out in the Cumberland Basin north of the Minudie Anticline on the Maringouin Peninsula of southeastern New Brunswick, and in northernmost Nova Scotia. Previous biostratigraphic [...]

Soils in boundary conditions of contrasting ecosystems generally show unique features. Transition often leads to changes in soil-forming processes, whereby the environment never comes to equilibrium and therefore the soil chemistry and mineralogy show different influences. Such an environment was analysed in the Saloum River basin, west-central Senegal. The objective was to identify the main pedogenic processes prevailing in this saline and acid pedoenvironment and to assess the influence of environmental factors (climate, topography, soil salinity and acidity) on local soil formation and mineral distribution. The terrace landscape is built up by a floodplain, a low terrace, which is still influenced by groundwater, and a middle terrace. The results show that soil properties are strongly influenced by hydrology, salinity and acidity in the entire toposequence: Glcyic Hyposalic and Hypersalic Solonchaks (Sulfatic) in the floodplain, Haplic Gleysols (Thionic) in the low terrace, and Endogleyic Arenosols in the middle terrace. The oxidation of pyrite followed by the redistribution of the main products ([Fe.sup.2+] and S[O.sub.4.sup.2-]) represents the major chemical process responsible for iron oxide and jarosite formation. Mineral distribution and crystallinity are linked to the landscape position, which controls the hydrological behaviour and reactions of Fe and S ions. Finally, we observed intrapedon processes such as gleysation, sulfidisation and sulfurisation, as well as interpedon processes such as salinisation, colluvio-alluviation and lateral eluviation. The combination of processes depends strongly on the landscape positions. Additional keywords: acidity, acid sulfate soil, iron oxide, jarosite, salinity, Senegal., Introduction Coastal landscapes around the world frequently contain acid sulfate soils (ASS). These are defined as soils that are severely acidic or have the potential to become acidic as a [...]