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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., [...]

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 [...]

Multivariate analysis of 197 well-preserved specimens among 11 species of late Late Ordovician (Katian and Hirnantian) plaesiomyid brachiopods from North America revealed two trends of morphological changes: (1) increasing globosity and dorsal convexity from the early to late Katian, and (2) coarser, but fewer ribs in species from the paleoequatorial intracratonic seas compared with species from the mid- to high-tropical pericratonic shelves and platforms. Another notable change, albeit not quantified, was the enlargement of cardinal process in plaesiomyids from early to late Katian, characterized by a predominantly trilobed cardinal process in the intracratonic species versus a bilobed cardinal process in pericratonic species. Increases in dorsal convexity and shell globosity are interpreted to have allowed for development of a larger lophophore, improving the capacity and efficiency of filter feeding and gas exchange. Smaller but more frequently bifurcating ribs would have led to more numerous setae near the margin of the shell, resulting in increased sensitivity to environmental stimuli. Increased size and number of lobes of the cardinal process would have allowed for larger diductor muscles to open a larger, heavier shell. In this study, two new species, Plaesiomys periosa sp. nov. and Plaesiomys lenzi sp. nov., are proposed, and two existing species are transferred from Dinorthis to Plaesiomys. Une analyse multivariee de 197 specimens bien preserves de 11 especes de brachiopodes plaesiomyides de la fin de l'Ordovicien tardif (Katien et Hirnantien) de l'Amerique du Nord revele deux tendances en ce qui concerne les changements morphologiques, a savoir: (1) l'augmentation de la globosite et de la convexite dorsale du Katien precoce au Katien tardif et (2) des cotes plus larges bien que moins nombreuses chez les especes de mers intracratoniques paleoequatoriales par rapport aux especes de plateaux ou plateformes pericratoniques des tropiques intermediaires ou hauts. Un autre changement notable, bien que non quantifie, est l'augmentation de la taille du processus cardinal chez les plaesiomyides du Katien precoce au Katien tardif, caracterises par un processus cardinal principalement trilobe chez les especes intracratoniques comparativement a un processus cardinal bilobe chez les especes pericratoniques. L'augmentation de la convexite dorsale et de la globosite de la coquille aurait rendu possible le developpement d'un lophophore plus grand, ameliorant ainsi la capacite et l'efficacite de l'alimentation par filtration et de l'echange de gaz. Des seta plus nombreuses pres de la bordure de la coquille decoulant de cotes plus petites, mais plus frequemment bifurquees, se seraient traduites par une sensibilite accrue aux stimuli ambiants. L'augmentation de la taille et du nombre des lobes du processus cardinal aurait donne lieu a des muscles divaricateurs plus grands capables d'ouvrir une coquille plus imposante etlourde. Deux nouvelles especes, Plaesiomys periosa sp. nov. et Plaesiomyslenzi sp. nov., sontproposees et deux especes existantes sont transferees de Dinorthis a Plaesiomys. [Traduit par la Redaction], Introduction Plaesiomyids constitute an orthide brachiopod family that became most common in Laurentia during the Late Ordovician. Most plaesiomyids belong to the subfamily Plaesiomyinae, characterized by large, costate to costellate, [...]

Enigmatic millimetre-scale micro-concretions with pseudocrystal faces and dominated by green clay minerals occur in unfossiliferous siliciclastic mudstone of the Lower Ordovician (479.0-466.0 Ma) Tonggao Formation, South China. The fossil-free mudstone unit is associated with local biodiversity decline. The mineralogy and mineral chemistry of these concretions were unknown previously, and this study comprises a preliminary investigation. The concretions are dominated by Fe-rich phyllosilicate minerals including glauconite and clinochlore, with minor quartz and traces of magnetite. The textural relations between the micro-concretions and the surrounding matrix, and the preservation of original mudstone laminations within the concretions, point to an origin during early diagenesis. The mineralogy and chemistry of these concretions are consistent with an origin in a restricted, hypersaline, relatively deep-water environment, in accordance with stratigraphical and paleonotological data. These micro-concretions provide clues for a stressed environment with poor water circulation and anomalies of salinity and oxygen. Des micro-concretions enigmatiques d'echelle millimetrique, avec des faces pseudocristallines et dominees par des mineraux argileux verts, se trouvent dans des mudstones siliclastiques non fossiliferes de la Formation de Tonggao de l'Ordovicien inferieur (479,0-166,0 Ma), dans le sud de la Chine. L'unite mudstone sans fossile est associee a un declin de la biodiversite locale. La mineralogie et la chimie des mineraux de ces concretions n' etaient pas connues anterieurement et la presente etude comprend une investigation preliminaire. Les concretions sont dominees par des mineraux phyllosilicates riches en Fe, incluant la glauconite et le clinochlore, avec un peu de quartz et des traces de magnetite. Les relations texturales entre les micro-concretions et la matrice environnante ainsi que la preservation des laminations originales du mudstone a l'interieur des concretions signalent une origine au debut d'une diagenese. La mineralogie et la chimie de ces concretions correspondent a une origine dans un environnement aqueux limite, hypersalin et relativement profond, ce qui concorde avec les donnees stratigraphiques et paleontologiques. Ces micro-concretions fournissent des indices qu'il s'agissait d'un environnement perturbe avec une mauvaise circulation d' eau et des teneurs anormales en sel et en oxygene. [Traduit par la Redaction], Introduction The Lower Ordovician (479.0-466.0 Ma) Tonggao Formation in Guizhou, South China (Fig. 1), contains abundant microconcretions of clay minerals, which occur in the largely unfossiliferous units of siliciclastic deposits [...]

Shelly communities and reef ecosystems represent the pinnacle of generic diversity and organizational complexity in marine environments. These systems are sensitive to climatic, tectonic, eustatic, and catastrophic changes, and their [...]

Abstract: The Early Silurian carbonate succession of Anticosti Island, eastern Canada, contains a rich and diverse pentameride brachiopod fauna. Multivariate analyses of 91 samples (total 17 230 specimens) confirm a [...]

Abstract: Brachiopods from the lower Tonggao Formation (Floian, late Early Ordovician) of Sandu, southeastern Guizhou Province, represent a deep-water benthic shelly fauna from the Jiangnan Slope facies of the South [...]

Abstract: Systematic and statistical study of brachiopods from the Dawan Formation of the Yichang area, western Hubei Province, central China, indicates that, at generic and specific levels, the α diversity [...]

Abstract: Primary δ[sup.18]O signals of 97 brachiopod shells from the Lower Silurian (Llandovery) carbonate succession of Anticosti Island were used to test the hypothesis of water-depth and water-temperature gradient for [...]

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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.)

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.)

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.)

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

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

The Early Devonian graptolite fauna of the Arctic Islands comprises the highest species content (17 species) in the world. In spite of this richness, no new species have been recognized; instead already-existing species, scattered around the then-known continents, suggest that relatively complete cosmopolitanism held sway for graptolites. Canadian Arctic biozonation is very similar to schemes elsewhere, consisting of the uniformis and hercynicus biozones in the Lochkovian, falcarius in the lower Pragian, and an expanded yukonensis Biozone in the upper Pragian and the lower Emsian. Three genera and 17 species are recognized: ' Monograptus' ( microdon cf. microdon, microdon curvatus); Neomonograptus (cf. atopus, aequabilis, bardoensis, falcarius, notoaequabilis); and Uncinatograptus ( birchensis, craigensis, hercynicus, langgunensis, parangustidens, subhercynicus, telleri, thomasi, uniformis, yukonensis). [ABSTRACT FROM AUTHOR]

Tangshanaspis Zhou and Zhang, 1978 (Family Missisquoiidae), has been reported widely from western North America and has been assigned invariably to a single species, T. depressa (Stitt, 1971 b). The base of the T. depressa Subzone as defined in Oklahoma is an important biostratigraphic datum for inter-regional correlation of uppermost Cambrian strata. Study of previously undescribed material in collections from Oklahoma shows that T. depressa is, in fact, a composite of cranidia and pygidia that belong to two stratigraphically segregated species in the Signal Mountain Formation. Tangshanaspis silveri n. sp. includes the pygidial morph originally attributed to T. depressa. Revision of the species from Oklahoma allows definition of a new biostratigraphic unit, the Tangshanaspis Zone, which is divided into a lower T. silveri Fauna and an overlying T. depressa Fauna; in addition to the eponymous species, the T. depressa Fauna includes pygidia that represent two additional species of Tangshanaspis that are placed in open nomenclature. Correlation with other areas suggests that the ' Missisquoia' mackenziensis Fauna of northern Canada may be equivalent to the T. silveri Fauna of Oklahoma, rather than a pre- Tangshanaspis interval that is unrepresented elsewhere in Laurentian North America. [ABSTRACT FROM AUTHOR]