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The Cambrian pre-salt dolomite sequence in the Tarim Basin is a target zone of great strategic significance for hydrocarbon exploration in the basin. Using the results of the interpretation of 3D seismic data from Lunnan and 2D seismic data covering the whole basin, and based on a synthesis of outcrop data, drilling data, well logs, core data, and thin-section data, and the findings from previous studies, this paper studies the characteristics of the facies of the Middle–Lower Cambrian in the platform area in the Tarim Basin, the formation and evolution of platform margins, and the sedimentary characteristics, lithofacies, and paleogeographic characteristics of the Middle–Lower Cambrian series. Based on the types of lithofacies and the seismic facies analysis, the sedimentary facies of the Middle–Lower Cambrian strata can be classified into the five types. From bottom to top, the Middle–Lower Cambrian have experienced several development stages, including the deposition of continental shelf sediments of the Yuertusi Formation, gently sloping non-rimmed platform margin sediments of the Xiaoerbulake Formation, weakly rimmed platform margin sediments of the Wusongger and Shayilike formations, and strongly rimmed platform margin sediments of the Awatage Formation. In each stage, the platform margin shifted further east relative to its location in the previous stage. Based on these results and previous studies, the lithofacies and paleogeography maps of the Middle–Lower Cambrian in the Tarim Basin are modified, and the implications for hydrocarbon exploration in this area are discussed. [ABSTRACT FROM AUTHOR]

Subaerial rise of Earth's first continents took place 3.3–3.2 Ga years ago. This had significant influence on the ocean, atmosphere, and biosphere. Two important sedimentological consequences of continental emersion were (1) development of terrestrial (alluvial fan–fluvial–aeolian) depositional systems and (2) formation of shallow-marine sedimentary basins near the continental margin. Late Paleoarchean–Neoarchean terrestrial deposits, including development of an extensive paleosol around 3.2 Ga, and Meso–Neoarchean shallow-marine deposits have been reported from the Singhbhum Craton, eastern India from several localities. However, lateral and vertical changes in sedimentary facies associations and stratigraphic correlation between these terrestrial to shallow-marine sedimentary deposits have not yet been investigated. In this paper, we have reviewed the sedimentological characteristics of Late Paleoarchean to Neoarchean (3.2–2.8 Ga) stratigraphic successions of the Singhbhum Craton and have discussed sea level change and mode of stratigraphic sequence building. Our analysis shows that Singhbhum granitoid complex was emplaced around 3.3 Ga in an intracontinental setting, resulting in high continental freeboard conditions that triggered terrestrial (alluvial fan–braided fluvial) sedimentation (Dhosrapahar Formation). Continental sedimentation continued until ca. 3.0 Ga. In the eastern (Simlipal Group), western (Birtola Formation), and southwestern (the Mankarchua, Mahagiri, and Keonjhar formations) parts, shallow-marine sedimentation occurred after 3.0 Ga as a result of transgression. However, in the northern part (Dhanjori Formation), continental sedimentation prevailed throughout the Archean. These Late Paleoarchean to Neoarchean terrestrial and near-coastal successions of Singhbhum Craton should be the prime targets for intense geobiological research. [ABSTRACT FROM AUTHOR]

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Detrital chromite is currently accumulating in the wave-influenced gravel-dominated shoreface of eastern Port au Port Bay of western Newfoundland adjacent to the mouth of Fox Island River. Chromium (Cr) concentrations of up to 7485 ppm occur in modern cross-bedded shallow marine gravel and pebbly sand facies sourced from rapidly eroding coastal cliffs cut in a lateglacial and early postglacial fan delta and raised beach facies. These sediments fill a broad coastal embayment and were deposited by a glacially influenced Fox Island River during a phase of low relative sea level following final deglaciation of the Newfoundland Ice Cap between approximately 13 700 years B.P. (ybp) and 9500 ybp. Since then, coastal outcrops of these raised sediments have undergone rapid erosion in response to ongoing postglacial sea level rise outpacing the rate of crustal recovery. Geochemical analysis of 1149 sediment samples across the entire Fox Island River watershed identifies relatively low Cr concentrations (maximum 1860 ppm) in glacial and fluvial sediments, including those areas adjacent to chromite-bearing rocks of the Bay of Islands Ophiolite Complex. Conversely, uplifted lateglacial shallow marine gravels and associated raised beach/nearshore deposits along the coast show elevated Cr concentrations up to 5400 ppm, highlighting the importance of marine concentration of glacially derived sediment during deglaciation. At the present day, chromite-bearing lateglacial sediment is being reworked and transported southwards by shore-parallel littoral currents resulting in reconcentration of Cr within a nearshore placer about 8 km long and 2 km wide, though the deposit may be more extensive offshore where it is likely covered by transgressive marine muds. The glacial and postglacial history of the Port au Port Bay area was widely replicated in other areas of ultrabasic rock along the western coast of Newfoundland and the results of this investigation may aid the search for other nearshore glacially influenced marine placers. [ABSTRACT FROM AUTHOR]

There are numerous Neoarchean metasedimentary rock packages in the Slave craton, and they serve as important archives of tectonic processes. Little is documented on the Neoarchean sedimentary packages of the Winter Lake greenstone belt of the central Slave craton, however, and their interpretation can aid in the understanding of the final stages of Slave craton amalgamation. This project investigates the depositional environments and tectonic settings of the Itchen Formation and Sherpa Formation of the Winter Lake greenstone belt. Our study provides constraints for reconstructing the Neoarchean evolution of the central Slave craton through bedrock mapping and facies analysis. The Itchen Formation consists of submature mudstone, siltstone, and sandstone, with preserved graded bedding, planar bedding, and flame structures. Unconformably overlying the Itchen Formation is the Sherpa Formation, which is dominated by polymictic conglomerates and coarse-grained sandstones with preserved cross-bedding, imbricated clasts, and scour surfaces. The Itchen Formation is interpreted to have been deposited in a convergent basin (i.e., retro-arc foreland basin), where two facies associations outline turbidite and suspension sedimentation consistent with submarine fan deposition on a continental slope and a basin floor environment. By contrast, the Sherpa Formation has three facies associations representing dominantly alluvial–fluvial environments in terrestrial–marine–lacustrine settings deposited in pull-apart basins resulting from transtensional forces associated with the Beniah fault zone. [ABSTRACT FROM AUTHOR]

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The Cretaceous Western Interior Basin reflects the interplay between the North American craton and allochthonous terranes to the west. We divide the basinal stratigraphy into three successions, Aptian–Albian, Cenomanian–Turonian, and Santonian–Maastrichtian, each related to periods of deformation in the adjacent fold-thrust belt. Here we focus on the Cenomanian–Turonian succession, where progressive west to east uplift and fluvial incision of older Aptian–Albian sedimentary rocks (Cedar Mtn–San Pitch–Thermopolis–Skull Creek–Mannville) are interpreted as a migrating forebulge. Uplift was underway at 103 Ma in the west (Paddy–Blackleaf–Muddy sandstones) and propagated eastward throughout the trough by 99.5 Ma (Viking–Bow Island–Newcastle sandstones). The incised fluvial valleys were subsequently filled by swampy and shallow marine facies, then overlain by dark, marine Neogastroplites-bearing shale and associated bentonites of the 100–97.5 Ma Shell Creek–Mowry–Slater River–Goodrich–Shaftesbury–Westgate shales. The shales are characterized by a distinctive condensed horizon with abundant fish scales, teeth, and bones. They are interpreted as outer-trench slope deposits, with the overlying anoxic horizon representing a starved isochronous unit formed atop the slope deposits. The starved horizon is overlain by prodeltaic muddy clinoforms of easterly migrating clastic wedges (Trevor–Dunvegan–Frontier–Cintura–Mexcala) that can be traced 800 km atop the fish-scale hash and contain hinterland-derived 99–90 Ma detrital zircons. Although the Western Interior Basin has long been considered a retro-arc trough, the overall succession instead suggests that the Cretaceous–Turonian part represents a collisional foredeep created during the ∼100 Ma collision between the arc-bearing Peninsular Ranges composite terrane and North America. The accretion brought tyrannosaurids, pachycephalosaurs, snakes, and marsupials to North America. [ABSTRACT FROM AUTHOR]

Reconstructing tectonic histories involving continental collision, subduction, and exhumation at plate-tectonic rates of ~1 cm/year, requires precise U-Pb zircon geochronology. The Western Gneiss Region has exceptional exposures of high-pressure (HP) and ultra-high-pressure (UHP) rocks. The strategy adopted here involved sampling eclogite and associated late unstrained pegmatites to acquire the time of eclogite crystallization and subsequent exhumation, respectively. The oldest eclogite sampled is 415 ±1 Ma from layered, probably UHP eclogite at Tevik, Averøya, also with a garnet-hornblende assemblage at 410 ±1 Ma. The Flem Gabbro eclogite margin, with implied UHP conditions, is 410 ±2 Ma. Hornblende eclogite at Seth, Lepsøya, never at UHP, is 412 ±2 Ma. These compare to Devonian ages of 401 ±1 Ma for overgrowths on Proterozoic baddeleyite in Selnes Gabbro, 402 ±2 Ma for coesite eclogite at Hareidlandet, 405-400 Ma for coesite eclogite at Flatraket, and 405 ±2 Ma for near-UHP eclogite at Hjelmelandsdalen. The 415 Ma eclogite at Tevik compares to granitic pegmatite in the same outcrop at 395.2 ±1.3 Ma and to pegmatite in eclogite at Aspøya at 395.3 ±2 Ma. The 410 Ma age at Flem compares to nearby pegmatite in eclogite at 396 ±4 Ma. Collectively, these results imply 14-20 million years between deep eclogite crystallization at ~130 km and return to amphibolite-facies conditions at ~30 km, with crystallization of locally derived granitoid melts. Nearby garnet-pyroxenite records older ages (~430) and greater depths (~200 km), but on similar exhumation paths at ~0.4-0.7 cm/year. La reconstruction d'historiques tectoniques impliquant des collisions continentales, de la subduction et de l'exhumation à des taux tectoniques d'environ 1 cm/année demande une géochronologie U-Pb sur zircon précise. La région du gneiss occidental de la Norvège présente des affleurements exceptionnels de roches ayant subi des pressions hautes (HP) et ultra-hautes (UHP). La stratégie adoptée ici était d'échantillonner l'éclogite et des pegmatites associées tardives n'ayant pas subi de contraintes afin d'obtenir respectivement le moment de cristallisation de l'éclogite et son exhumation subséquente. L'éclogite échantillonnée la plus ancienne a 415 ±1 Ma et provient d'une éclogite, probablement formée à ultra-haute pression, située à Tevik, Averøya, avec un assemblage grenat-hornblende datant de 410 ±1 Ma. La bordure éclogite du gabbro Flem, possédant des conditions UHP, est âgée de 410 ±2 Ma. L'éclogite à hornblende à Seth, Lepsøya, n'ayant jamais subi de UHP, date de 412 ±2 Ma. Elles se comparent avec des âges dévoniens de 401 ±1 Ma pour des accroissements sur une baddeleyite datant du Protérozoïque dans le gabbro Selnes, de 402 ±2 Ma pour l'éclogite coésite à Hareidlandet, de 405-400 Ma pour l'éclogite coésite à Flatraket et de 405 ±2 Ma pour l'éclogite presque UHP à Hjelmelandsdalen. À Tevik, l'éclogite datant de 415 Ma peut être comparée à une pegmatite granitique dans le même affleurement et datant de 395,2 ±1,3 Ma et à une pegmatite dans l'éclogite à Aspøya datant de 395,3 ±2 Ma. L'âge de 410 Ma à Flem se compare bien à celui de la pegmatite dans une éclogite avoisinante datant de 396 ±4 Ma. Ensemble, ces résultats signifient une période de 14 à 20 Ma entre la cristallisation en profondeur de l'éclogite, à ~130 km, et le retour aux conditions du faciès des amphibolites à ~30 km, avec la cristallisation de granitoïdes en fusion de provenance locale. La pyroxénite à grenat avoisinante enregistre des âges plus anciens (~430 Ma) et une plus grande profondeur (~200 km) mais avec des cheminements d'exhumation similaires d'environ 0,4-0,7 cm/année. [ABSTRACT FROM AUTHOR]

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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.)

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.)

Kakanui volcaniclastic deposits on the South Island of New Zealand are the remnants of two late Eocene to early Oligocene Surtseyan-type cones. Eruptive-dominated material of the (i) stratified tuff and lapilli tuff, and (ii) lapilli tuff breccia lithofacies and post-eruptive debris of the (iii) shell-rich tuff and lapilli tuff, and (iv) chaotic and cross-bedded tuff and lapilli tuff lithofacies compose the deposits. The 9–250 m thick stratified tuff and lapilli tuff contains grain-flow deposits originating from low-volume tephra jets and local thinning and fining upward sequences that formed from density currents during sustained uprush. The lapilli tuff breccia, up to 4.5 m thick, contains inward-dipping beds deposited via debris flows along inner-cone walls. Burrows and articulated shells in the 2–4 m thick shell-rich tuff and lapilli tuff indicate volcanic quiescence and low sedimentation rates, whereas shell fragments upsection signal increased wave and current activity. Burrows, pyrite concretions, and mudstone in the lower part of the 26 m thick chaotic tuff and lapilli tuff indicate suspension deposition and cessation in pyroclastic volcanism. High-angle trough cross-beds and limestone rip-up fragments upsection are consistent with wave-induced current reworking. The depositional model involves a Surtseyan-type eruption on a continental shelf, followed by colonization of organisms on the tops of planed-off cones. The Kakanui deposits comprise a cluster of cones constituting part of a late Eocene – early Oligocene monogenetic volcanic field. The Kakanui succession provides an opportunity to study deposits that form from explosive subaqueous pyroclastic eruptions and wave-dominated deposition and erosion. Les dépôts volcanoclastiques Kakanui de l’Île du Sud de la Nouvelle-Zélande sont les lambeaux d’érosion de deux cônes de type surtseyen datant de l’Éocène tardif à l’Oligocène précoce. Les dépôts sont composés principalement de matériaux éruptifs composés (i) de tufs stratifiés et de tufs à lapilli et (ii) de lithofaciès de brèches de tuf à lapilli et de débris post-éruption composés (iii) de tufs coquilliers et de tufs à lapilli et (iv) de tufs chaotiques et à laminations croisées et de facies de tufs à lapilli. Le tuf stratifié et à lapilli d’une épaisseur de 9 à 250 mètres contient des dépôts d’écoulement de grains provenant de jets de tephra à faible volume et des séquences qui s’amincissent et dont les grains deviennent plus fins vers le sommet; ces séquences proviennent de courants de densité présents durant la montée soutenue de la lave. Les brèches de tuf à lapilli, atteignant des épaisseurs de 4,5 m contiennent des lits à pendage retourné déposés par des écoulements de débris le long des murs internes du cône. Des tunnels et des coquillages articulés dans le tuf riche en coquillages, d’une épaisseur de 2 à 4 m, combinés au tuf à lapilli, indiquent un volcan au repos et de faibles taux de sédimentation. Par contre, des fragments de coquillages dans le haut de la section sont un indice de plus de vagues et de courants. Les tunnels, les concrétions de pyrite et les mudstones dans la partie inférieure du tuf chaotique d’une épaisseur de 26 m et le tuf à lapilli indiquent une déposition de la matière en suspension et l’arrêt du volcanisme pyroclastique. Les lits à stratification entrecroisée dont l’angle est élevé et des fragments de calcaire arrachés concordent avec un remaniement par un courant induit par les vagues. Le modèle de déposition implique une éruption de type surtseyen sur un plateau continental, suivie d’une colonisation d’organismes sur les sommets des cônes tronqués. Les dépôts Kakanui comprennent une grappe de cônes qui font partie d’un champ volcanique monogénique datant de l’Éocène tardif – Oligocène précoce. La suite Kakanui fournit la possibilité d’étudier des dépôts qui se sont formés à partir d’éruptions explosives pyroclastiques subaquatiques et de déposition dominée par les vagues et par l’érosion. [ABSTRACT FROM AUTHOR]

New Rb–Sr phlogopite and U–Pb perovskite age determinations for 12 of 38 known ultramafic bodies in the Buffalo Head Hills area of north-central Alberta show that kimberlitic magmatism occurred in at least two separate episodes during Late Cretaceous and Paleocene time. Nine kimberlites yield Coniacian to Campanian ages of between 88 ±5 Ma (U–Pb perovskite, K5A) and 81.2 ±2.3 Ma (Rb–Sr phlogopite, K252). A Danian U–Pb perovskite isochron age of 63.5 ±0.7 Ma was obtained for the BM2 kimberlite, and Selandian Rb–Sr ages of 59.6 ±2.8 and 60.3 ±0.8 Ma were determined for the K1A and K19 bodies, respectively. These specific periods of magmatism correspond to characteristic intra-field features such as kimberlite spatial distribution, diamond content, rock classification, and mechanisms of emplacement. The ~88–81 Ma group generally occurs in the northwestern part of the field and defines the diamond window for the Buffalo Head Hills kimberlite field. This volcanism is contemporaneous with sedimentary host rock deposition, which has important implications for the size and morphological complexity of the kimberlite bodies. The ~64 Ma BM2 body represents the only known occurrence of hypabyssal-facies kimberlite in this field and is similar in terms of source composition to the ~88–81 Ma kimberlites, but is not diamond bearing. The ~60 Ma group occurs in the southwestern part of the field, is derived from a weakly diamondiferous – barren hybrid ultramafic source and features bodies that are eroded to present-day stratigraphic levels. De nouvelles déterminations d’âges Rb–Sr sur phlogopite et U–Pb sur pérovskite pour 12 des 38 amas ultramafiques connus dans le secteur de Buffalo Head Hills, dans le centre-nord de l’Alberta, montrent que le magmatisme kimberlitique s’est produit au moins au cours de deux épisodes distincts aux époques du Crétacé tardif et du Paléocène. Neuf kimberlites ont donné des âges Coniacien à Campanien entre 88 ±5 Ma (U–Pb sur pérovskite, K5A) et 81,2 ±2,3 Ma (Rb–Sr sur phlogopite, K252). Un âge isochrone Danien U–Pb sur pérovskite de 63,5 ±0,7 Ma a été obtenu pour la kimberlite BM2 et des âges Sélandien Rb-Sr de 59,6 ±2,8 et de 60,3 ±0,8 Ma ont été déterminés respectivement pour les amas K1A et K19. Ces périodes spécifiques de magmatisme correspondent à des structures caractéristiques intra-champs, telles que la distribution spatiale de la kimberlite, le contenu en diamants, la classification de la roche et les mécanismes de mise en place. Le groupe dont l’âge est d’environ 88 à 81 Ma, se retrouve généralement dans la partie nord-ouest du champ et il définit la fenêtre diamantifère du champ de kimberlites Buffalo Head Hills. Ce volcanisme est contemporain de la déposition des roches encaissantes sédimentaires, ce qui a des implications significatives pour la dimension et la complexité morphologique des amas de kimberlite. L’amas BM2, ~64 Ma, représente la seule occurrence connue de kimberlite à faciès hypabyssal dans ce champ et sa composition source est similaire aux kimberlites ~88 à 81 Ma, mais il n’est pas diamantifère. Le groupe ~60 Ma se trouve dans la partie sud-ouest du champ, il provient d’une source ultramafique hybride faiblement diamantifère – stérile et il comporte des amas qui ont été érodés aux niveaux stratigraphiques actuels. [ABSTRACT FROM AUTHOR]

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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.)

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.)

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.)

Deals with a study which documented the development of comparable shallow-marine facies in the terminal Arenig of Avalon from eastern Newfoundland to southern New England. Limestone lithology; Faunas; Discussion; Systematic paleontology; Discussion.

Distribution of facies in the lower half of the Bylot Supergroup suggests overall westward deepening of the Mesoproterozoic Borden Basin. In marked contrast, the upper half of the succession records a reversal in the overall bathymetric trend, such that the eastern portion underwent relative deepening as the west experienced relative shallowing. Strata deposited during this reversal belong to the Victor Bay Formation, a ramp composed predominantly of limestone. Karsting of carbonate strata and development of an angular unconformity in the west contrast with back-stepping and drowning of the ramp in the east, followed by mantling by deep-water limestone, carbonaceous carbonate, and turbidites. Increased accommodation space during this time, via both tectonic subsidence and eustatic sea-level rise, led to a profusion of stromatolite pinnacle reefs and large biostromes. The reversal of basin polarity is best reconciled with development of a distal foreland basin superimposed on the Borden aulacogen. Crustal rethickening and uplift occurred along reactivated basement faults during an eastward-directed compressional event and could be related to thrusting of similar age and vergence in the Coppermine River Group of northwestern Canada.La distribution des faciès dans la moitié inférieure du Supergroupe de Bylot suggère un approfondissement général vers l'ouest du bassin de Borden (Mésoprotérozoïque). Par contre, la moitié supérieure de la séquence montre un renversement de la tendance bathymétrique, de telle façon que la partie orientale subissait un approfondissement relatif alors que la partie occidentale subissait un rehaussement relatif. Les strates déposées au cours de ce renversement appartiennent à la Formation de Victor Bay, une rampe composée surtout de calcaire. Le développement de karsts dans les strates calcareuses et le développement d'une discordance angulaire à l'ouest contrastent avec la rétrogradation et l'ennoiement de la rampe à l'est, suivi d'un recouvrement par des calcaires d'eau profonde, des carbonates carbonés et des turbidites. Durant ce temps, une augmentation de l'espace disponible, grâce à la subsidence tectonique et à l'élévation eustatique du niveau de la mer, a conduit à une profusion de récif-pinacles à stromatolites et à de vastes biostromes. L'inversion de la polarité du bassin concorde très bien avec le développement d'un bassin d'avant-pays distal surimposé à l'aulacogène de Borden. Un nouvel épaississement et un rehaussement de la croûte se sont produits le long de failles du socle réactivées lors d'un événement de compression dirigé vers l'est et qui pourrait être relié à un chevauchement d'âge et de vergence similaires dans le Groupe de Coppermine River du nord-ouest du Canada.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]