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Dalmanelloid brachiopod shells were collected from the Upper Ordovician Lexington Formation (lower Katian) of Kentucky, Sheguindah Shale (middle Katian) on Manitoulin Island, Ontario, and the Stony Mountain Formation (upper Katian) in the Winnipeg area, Manitoba. They were investigated to test the hypothesis of paleo-latitudinal zonation of the shelly benthos. A multi-technique approach was applied to evaluate the petrographic and geochemical (isotopic and elemental) preservation of the secondary layer of shells. Preliminary conventional microscopy, cathodoluminescence (CL), and scanning electron microscopy (SEM) confirmed the retention of primary shell ultrastructure (prismatic low-Mg calcite). The geochemical diagenesis proxies (e.g., Sr, Mn, Fe, and [summation]REE) show insignificant correlations with the [delta][.sup.18]O and [delta][.sup.13]C values, thus supporting the preservation of at least near-primary geochemical compositions. Among the three lots of shells, the mean [delta][.sup.18]O value is the highest in those from the Lexington Formation (-4.5[per thousand] [+ or -] 0.3[per thousand] VPDB), lowest from the Stony Mountain Formation (-6.8[per thousand] [+ or -] 0.4[per thousand] VPDB), and intermediate from the Sheguindah Shale (-6.0[per thousand] [+ or -] 0.8[per thousand] VPDB). The relative gradient in [delta][.sup.18]O increase is in agreement with the paleo-latitudinal gradient, with Kentucky in subtropical, southern Ontario in mid-tropical, and southern Manitoba in subequatorial latitudes. The Lexington Formation shells also have the highest mean [delta][.sup.13]C value (0.8[per thousand] [+ or -] 0.2[per thousand] VPDB) and relatively high P contents (170 [+ or -] 27 ppm), suggesting higher organic productivity, which is consistent with previous interpretation of frequent upwelling of nutrient-rich cool waters along the southeastern margin of Laurentia during the Katian. The Lexington shells also have a lower mean Th/U (0.6 [+ or -] 0.6), which is consistent with blooming organic productivity that likely led to more consumption of oxygen in the water column. Des coquilles de brachiopodes dalmanelloides ont ete recueillies de la Formation de Lexington de l'Ordovicien superieur (Katien inferieur) du Kentucky, du shale de Sheguindah (Katien moyen) de l'ile Manitoulin (Ontario) et de la Formation de Stony Mountain (Katien superieur) de la region de Winnipeg (Manitoba). Elles ont ete examinees pour verifier l'hypothese d'une zonation paleolatitudinale du benthos a coquilles. Une approche faisant appel a plusieurs techniques a ete utilisee pour evaluer la preservation petrographique et geochimique (isotopique et elementaire) de la couche secondaire des coquilles. La microscopie classique preliminaire, la cathodoluminescence (CL) et la microscopie electronique a balayage (MEB) ont confirme la retention d'une ultrastructure primaire dans les coquilles (calcite pauvre en Mg prismatique). Des caracteres geochimiques temoignant de la diagenese (p. ex. Sr, Mn, Fe et [summation]ETR) montrent des correlations significatives avec les valeurs de [delta][.sup.18]O et de [delta][.sup.13]C, appuyant l'interpretation de la preservation de compositions geochimiques au moins quasi primaires. Parmi les trois lots de coquilles, la valeur de [delta][.sup.18]O moyenne est la plus elevee pour celui de la Formation de Lexington (-4,5 [per thousand] [+ or -] 0,3 [per thousand] VPDB), la plus faible pour la Formation de Stony Mountain (-6,8 [per thousand] [+ or -] 0,4 [per thousand] VPDB) et intermediaire pour le shale de Sheguindah (-6,0 [per thousand] [+ or -] 0,8 [per thousand] VPDB). Le gradient relatif d'augmentation du [delta][.sup.18]O concorde avec le gradient paleolatitudinal dans lequel le Kentucky se trouve a des latitudes subtropicales, le sud de l'Ontario, a des latitudes mid-tropicales et le sud du Manitoba, a des latitudes subequatoriales. Les coquilles de la Formation de Lexington presentent egalement le [delta][.sup.13]C moyen le plus eleve (0,8 [per thousand] [+ or -] 0,2 [per thousand] VPDB) et des concentrations de P relativement fortes (170 [+ or -] 27 ppm), ce qui indiquerait une plus grande productivite organique, en accord avec l'interpretation anterieure de remontees frequentes d'eaux froides riches en nutriments le long de la bordure sud-est de la Laurentie au Katien. Les coquilles de la Formation de Lexington ont aussi un rapport Th/U moyen plus faible (0,6 [+ or -] 0,6), ce qui concorde avec une productivite organique fleurissante qui s'est vraisemblablement traduite par une consommation d'oxygene accrue dans la colonne d'eau. [Traduit par la Redaction], Introduction The abundance of planktonic and benthic foraminifers in the Cenozoic marine carbonates provided suitable material for the geochemical studies that reconstructed the environmental variations during that time interval (e.g., [...]

An unusually rich and diverse suite of virgianid brachiopods, hitherto poorly known, is systematically described here for the first time from the Ordovician–Silurian boundary interval (late Katian – Aeronian) of North Greenland. The Late Ordovician virgianids comprise typical taxa of the warm‐water Tcherskidium fauna (e.g. Tcherskidium tenuicostatum, Proconchidium schleyi, Holorhynchus giganteus and Deloprosopus dawesi sp. nov.). Among the early Silurian taxa, Virgiana hursti sp. nov. occurs as abundant shell beds, similar to other congeneric species in Laurentia, but has somewhat larger internal skeletal structures, albeit not as extravagantly developed as in the late Katian virgianids; Borealoides balderi gen. et sp. nov. shows extreme thickening of the shell wall and internal structures, approaching the extravagant calcification of Katian virgianids. The highly distinctive mid‐Aeronian stricklandioid brachiopod genus, Kulumbella, characterized by a shell with criss‐cross (divaricate) ribbing, also occurs in North Greenland, represented by K. heimdali sp. nov., which has the largest and most strongly biconvex shells for the genus. Palaeogeographically, the Late Ordovician virgianid fauna of Laurentia was highly distinct, confined to the low–mid tropical latitudes north of the palaeoequator. In comparison, the early Silurian (Rhuddanian) Virgiana and some related taxa in Laurentia spanned the tropics of both hemispheres, forming extensive shell beds in carbonate basins, although Borealis and Borealoides gen. nov. remained confined largely to the northern hemisphere, suggesting a certain level of provincialism extending into the earliest Silurian. A palaeoecological preference for warm‐water carbonate settings would explain the unusual abundance and richness of the virgianid faunas in North Greenland. [ABSTRACT FROM AUTHOR]

Abstract: The Kettle Point Formation of southwestern Ontario consists of intervals of organic-rich interlaminated black shale interbedded with organic-poor greyish green mudstones and rare red beds, separated by metre-scale sequences [...]

Pentameroides is a large-shelled pentameride brachiopod, which was widespread throughout Laurentia in the early Silurian (Telychian). Evolving from Pentamerus in the early Telychian, it dispersed from its subtropical--high tropical origin [...]

The Late Ordovician (late Katian) Tcherskidium fauna consisted of large- and thick-shelled virgianid pentamerid brachiopods characterized by large and ribbed shells of Tcherskidium and Proconchidium and usually associated with Holorhynchus, Deloprosopus, and Eoconchidium. This unique fauna was widely distributed across several tectonic plates, largely confined to the paleoequatorial and especially the northern paleotropical zones, such as northern Laurentia, accretionary terranes of Alaska, Kolyma, Baltica, Siberia, Kazakh and adjacent terranes, and South China. In Laurentia, the eponymous genus Tcherskidium was predominant in regions north of the paleoequator and, in sharp contrast, was absent south of the paleoequator. In this study, Tcherskidium lonei n. sp. and Proconchidium schleyi n. sp. are described from Alaska and North Greenland, respectively, adding new data on the Tcherskidium fauna of the Late Ordovician Northern Hemisphere. Shell gigantism, together with the sharp paleobiogeographic division, suggests that the Late Ordovician (late Katian) Northern Hemisphere had a prevailing warm-water mass, probably due to the lack of large landmass beyond the northern tropics. This was in sharp contrast to the Southern Hemisphere, which was frequently influenced by cold-water invasions from the ice-bearing Gondwana supercontinent centered on the South Pole. UUID: http://www.zoobank.org/25d9b772-bd7d-4ad6-bfc6-ba02b1567cf3 [ABSTRACT FROM AUTHOR]

The Beishan orogenic zone is a key area to understand evolution of the Central Asian Orogenic Belt that is an accretionary factory well‐enough preserved in the Paleozoic. In early Paleozoic, the tectonic mélange zone containing the coherent unit and mélange unit is triggered by the complicated accretionary process of the Beishan area. The early Paleozoic tectonic evolution of the Beishan orogenic zone is investigated in this study using sedimentology and stratigraphic correlations of the lowe Paleozoic deposits. From the Cambrian to the middle Ordovician, this region was characterized by geographically extensive, flat‐bedded siliceous mudstone, indicating the existence of a large ocean basin. The oceanic plate entered the convergence phase in terms of the Wilson Circle during the Middle Ordovician, when numerous magmatic arcs formed along two opposite sides of the ocean. The magmatic arcs became the widest during the Silurian, suggesting that the Hongliuhe‐Niujuanzi‐Xichangjing Ocean (HNX; a southern branch of the Paleo Asian Ocean) was reduced to a small residual ocean in the central Beishan region by that time, and probably lasted till the Carboniferous or later by newly published data. [ABSTRACT FROM AUTHOR]

A Late Ordovician brachiopod fauna from the Black River quadrangle (D-1 1:63,360 scale) of east-central Alaska comprises taxa typical of the Late Ordovician brachiopod fauna in the pericratonic epeiric seas of Laurentia, including Hesperorthis pyramidalis (Twenhofel, 1928), Plaesiomys occidentalis (Okulitch, 1943), Eoplectodonta sp., Holtehdalina sp., Leptaena sp., Brevilamnulella minuta n. sp., Tcherskidium tenuicostatum n. sp., Rhynchotrema iowense Wang, 1949, and Whitfieldella sp. The presence of Plaesiomys occidentalis and Tcherskidium tenuicostata n. sp. indicates a latest Katian age by correlation with similar species in the Mackenzie Mountains, southern Manitoba, Anticosti Island, the American midcontinent, Kolyma, and Siberia. Cluster analysis based on 20 well-studied late Katian brachiopod faunas from various regions within Laurentia and elsewhere in other tectonic plates suggests that the small brachiopod faunule from Alaska has the strongest paleobiogeographic affinity with Laurentia, confirming that the Black River quadrangle of Alaska was part of Laurentia during the Late Ordovician. UUID: http://zoobank.org/6b387856-61d5-4685-a592-faf5287c1e0f [ABSTRACT FROM AUTHOR]

While it is well established that the shapes and sizes of shells are strongly phylogenetically controlled, little is known about the phylogenetic constraints on shell thickness. Yet, shell thickness is likely to be sensitive to environmental fluctuations and has the potential to illuminate environmental perturbations through deep time. Here we systematically quantify the thickness of the anterior brachiopod shell which protects the filtration chamber and is thus considered functionally homologous across higher taxa of brachiopods. Our data come from 66 genera and 10 different orders and shows well‐defined upper and lower boundaries of anterior shell thickness. For Ordovician and Silurian brachiopods we find significant order‐level differences and a trend of increasing shell thickness with water depth. Modern (Cenozoic) brachiopods, by comparison, fall into the lower half of observed shell thicknesses. Among Ordovician–Silurian brachiopods, older stocks commonly have thicker shells, and thick‐shelled taxa contributed more prominently to the Great Ordovician Biodiversification but suffered more severely during the Late Ordovician Mass Extinction. Our data highlight a significant reduction in maximum and minimum shell thickness following the Late Ordovician mass extinction. This points towards stronger selection pressure for energy‐efficient shell secretion during times of crisis. [ABSTRACT FROM AUTHOR]

ABSTRACT Middle Ordovician iron ooids in the Upper Yangtze region of South China are composed mainly of hematite and/or chamosite, found in mixed siliciclastic and carbonate successions, with hematitic ooids occurring in the west, and predominantly chamositic ooids in the east of the study area. In the three iron ooid‐bearing Middle–Upper Ordovician successions, 19 microfacies are recognized and grouped into eight facies associations, representing a shallow‐water mosaic comprising restricted and semi‐restricted lagoons, and open marine subtidal deposits interfingering with tidal flat and shoal facies. Hematitic ooids with well‐sorted and well‐rounded quartz grains formed in the transgressive shoal setting when the depositional environments changed from restricted lagoon to bioclast–quartz shoal and open marine subtidal. Episodic stasis and erosional intervals during transgression controlled the formation of hematite‐rich and mixed hematite–chamosite laminae within the cortices of hematitic ooids. In contrast, chamositic ooids formed in a semi‐restricted lagoonal environment, under long‐term transgressive condensation. Alternating episodes of relatively oxic conditions with thriving organisms and eutrophication‐driven anoxia resulted in the alternation of porous and dense laminae consisting mainly of chamosite in chamositic ooids. The stromatolite‐like cauliflower structures associated with chamositic ooids suggest microbial activity that promoted iron concentration, similar to the origin of approximately coeval iron‐rich oncoids in South China. Various iron ooid types demonstrate that these coated grains could form in a range of depositional setting and palaeooceanographic conditions on a generally shallow‐marine platform during the Ordovician. [ABSTRACT FROM AUTHOR]

Iron‐rich nodules occur on the Yangtze Platform, South China, especially along the marginal area, during the late Middle and early Late Ordovician (Darriwilian–Sandbian). Based on the study of samples from the Daling section, Anhui Province, these nodules include: (1) oncoids; (2) coated bioclasts; and (3) coated micritic intraclasts, all of which potentially have a similar biological origin. The nodule‐bearing strata were deposited in a midouter ramp setting, indicating sediment starvation and open marine conditions, possibly combined with anoxia in deeper basinal areas and cool water upwelling during the formation of the nodules, rather than terrestrial input or local tectonic movement. The widespread distribution of iron‐rich nodules at this time was probably favoured by high sea level and cooling climate, conditions that simultaneously favoured the evolutionary radiations of the GOBE in South China. Thus, these nodules form a time‐specific signature of a critical time in the evolution of the marine ecosystem in the context of local environmental background along the marginal Yangtze Platform. [ABSTRACT FROM AUTHOR]

The Late Ordovician marks an epoch of substantial change during Earth’s geologic history. It documents the first mass extinction event of the Phanerozoic, which wiped out a plethora of marine genera. Though signatures of the extinction event are quite evident on the species level, there are many underlying uncertainties as to which factors drove the near destruction of Ordovician marine life. The exact causes and contributing factors of the Late Ordovician Mass Extinction (LOME) are highly debated. Previous studies propose processes such as redox shifts, volcanism, deep-water anoxia, low atmospheric oxygen, or excess CO2 as significant influencers. In this study, we utilized a multi-archive/proxy approach in reconstructing paleoenvironmental, stratigraphic, chronologic, and diagenetic signatures of halite and carbonate sequences from two localities containing the Ordovician–Silurian boundary. Our preliminary findings suggest that an abrupt, multi-pulsed glaciation was probably the main driver of the LOME. However, the exact duration, intensity, and number of cooling pulses are still up to interpretation and will require additional geochemical work to paint the entire picture. Samples were obtained from two localities of similar low paleo-latitudes. Marine halite and carbonate were obtained from the upper Ordovician Red Head Rapids Formation, Hudson Bay Basin, Canada. Another suite of halite was collected from the Ordovician/Silurian Mallowa Salt Formation, Canning Basin, Western Australia. The diagenetic integrity of Red Head Rapids halite and carbonate were assessed through strontium isotope analysis. Since the strontium isotope remains in equilibrium with seawater, we can cross-analyse the preservation potentials of both marine archives. All sample results lay within the ± 0.00006 ‰ natural variation of 87Sr/86Sr measured in modern marine counterparts, providing evidence of primary material and accurate paleo-interpretations. Trace element chemistry study was conducted on halite samples from both localities. Previous studies suggested that the spikes of Hg, Mo, and U concentrations signify the aftermath of a greenhouse event that triggered the expansion of deep-water anoxia. Furthermore, heightened volcanic activity led to significant greenhouse gas emissions and produced a period of warming. Instead, our halite Hg, Mo and U concentrations are extremely low, many below detection limits, which correspond to glacial signatures of an icehouse. Interpretation of the sedimentary cerium anomaly of the Red Head Rapids and Mallowa salts also revealed characteristics of an oxygenated marine environment, with all calculated values below the threshold, typical of anoxia. Rigorous halite fluid inclusion analysis was conducted to qualitatively distinguish between primary and secondary material based on size, shape, orientation, and multiple growth pat­terns. Microthermometry homogenization temperatures derived quantitative distinctions between primary and secondary fluid inclusions of preserved and altered material, respectively. Paleotemperatures of primary fluid inclusions exhibited oscillations that were evident of daily/seasonal variation of inter- and/or glacial times, averaging approximately 24.2°C ± 0.5°C for the latest-Ordovician–earliest-Silurian. Apart from minor fluctuations, we noticed up to four major cool­ing pulses associated with the major glaciation characterizing the latest-Ordovician–earliest-Silurian time. [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.)

Pentameroides is a large-shelled pentameride brachiopod, which was widespread throughout Laurentia in the early Silurian (Telychian). Evolving from Pentamerus in the early Telychian, it dispersed from its subtropical - high tropical origin to subequatorial intracratonic seas by the late Llandovery. In this study, large collections of reef-dwelling Pentameroides septentrionalis from the Attawapiskat Formation, Akimiski Island, Nunavut, and level-bottom-inhabiting Pentameroides subrectus from the Fossil Hill Formation, Manitoulin Island, Ontario, and the Jupiter Formation, Anticosti Island, Quebec, were biometrically analyzed for seven external morphological features. Bivariate and ordination analysis (principal components analysis) revealed that P. septentrionalis has a more globose, more biconvex shell with a larger ventral umbo than P. subrectus. These morphological differences, coupled with their excellent preservation in shallow-water reefal environments, suggest that P. septentrionalis was adapted to a relatively low-turbulence, hurricane-free, nutrient-stressed environment near the equator (<10°S) while P. subrectus lived in storm-dominated higher tropical latitudes (∼15°S-25°S). This interpretation is corroborated by the morphology of level-bottom-dwelling Harpidium and Sulcipentamerus from the paleoequatorial lower Silurian of North Greenland, which exhibit morphological features similar to those of P. septentrionalis, even though they did not inhabit a reefal environment. Principal components analysis reveals that P. septentrionalis resembles P. subrectus in early ontogeny, suggesting that P. septentrionalis evolved from P. subrectus as it moved northwards from high tropical to near-equatorial settings. [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.)

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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.)

An introduction is presented in which the editor discusses various reports within the issue on topics including conodont biostratigraphy, conodont fauna of Xiushan Formation in South China; and morphological modifications and clines of pentamerid shells.

The article discusses various reports published within the issue which includes thorough and useful synopsis of previously published data on Silurian acritarchs from China and study of clay mineralogy and chemistry to interpret the changing climatic conditions related to the rise of the Caledonide mountains.

One of the best-exposed and most complete stratigraphic records from paleotropical areas spanning the Ordovician-Silurian (O-S) boundary is located on Anticosti Island, eastern Canada. Our study is the first one to sample strata superbly exposed at low tide along the west coast of Anticosti Island, thus providing a previously unexploited, nearly complete stratigraphic interval (∼300 m) at the O-S boundary for δ13C chemostratigraphy. A new high-resolution δ13C curve with more than 500 data points spaced at every ∼0.5 m has been produced, rectifying important pitfalls of previously published δ13C curves (i.e., low sampling resolution, variable sampling intervals, stratigraphic gaps). This new high-resolution δ13C curve displays a lower and an upper positive Hirnantian Isotope Carbon Excursion (HICE) recognized elsewhere around the globe. The ascending limb of the lower HICE starting from baseline values of +0.5‰ corresponds to the upper 20 m of the late Katian Vauréal Formation, but δ13C peak values of +2.5‰ occur in the lower part of the Hirnantian Ellis Bay Formation. In spite of a δ13C record segmented by a few stratigraphic hiatuses, the upper HICE, with its peak values of +4.5‰, is well recorded in the upper part of the Hirnantian Ellis Bay Formation. When compared with sections from around the globe, our δ13C curve displays a distinct long-term trend with a long sustained lower HICE followed abruptly by the upper HICE and return to baseline values of +0.5‰ prior to the Rhuddanian. The continued descending isotopic trend well into the Becscie Formation suggests that the O-S boundary may occur at a higher stratigraphic level (up to 30 m) than previously interpreted. Active subsidence combined with moderate initial water depths prior to the Hirnantian were key factors controlling the deposition of a thick O-S sedimentary succession with a few hiatuses on Anticosti Island and capturing a comprehensive, reliable δ13C record across this interval. [ABSTRACT FROM AUTHOR]

The Kettle Point Formation of southwestern Ontario consists of intervals of organic-rich interlaminated black shale interbedded with organic-poor greyish green mudstones and rare red beds, separated by metre-scale sequences of non-interlaminated black shale. The formation shows a largely consistent background value for the black shales around −20‰ δ34S, punctuated by a substantial positive excursion of ∼32‰ (up to +12.87‰) that coincides with a significant interval of greyish green mudstone and red beds. Lithological and geochemical data indicate that the black shales were deposited during periods of anoxia, with thick intervals of non-interlaminated black shales recording the peak of anoxia, whereas the greyish green mudstones record deposition in more oxygenated environments. Relative water depth is interpreted as the key control on the vertical and lateral distribution of the Kettle Point lithofacies. Interbedded black shales and greyish green mudstones were deposited in relatively shallow waters, where minor, short-lived falls in relative sea level promoted dysoxic to oxic conditions and the deposition of organic-poor lithologies. Non-interlaminated black shales are indicative of substantial rises in relative sea level, resulting in widespread anoxia and the deposition of thicker and more laterally extensive packages of organic-rich sediment. The formation of black shales in relatively shallow waters in southwestern Ontario implies that the extensive deposition of organic-rich sediment across eastern North America during the Late Devonian was a product of widespread anoxia related to restricted circulation in intracratonic and foreland basin depositional centers. [ABSTRACT FROM AUTHOR]