18 research outputs found

    Sedimentology and depositional environment of the middle Cambrian Manuels River Formation in the type locality at Conception Bay South, Newfoundland, Canada

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    A detailed bed-by-bed study of fossiliferous, marine, grey to black shales of the middle Cambrian (Drumian, Cambrian Series 3) Manuels River Formation along its type locality in Newfoundland, Canada, was carried out and provides insight into the sedimentology, depositional environment, palaeogeography and climatology of the area. The formation was deposited on the microcontinent Avalonia, the largest terrane of the peri-Gondwanan realm situated in temperate latitudes. The partly organic-rich (up to 3.36 % TOC) shales of the succession were deposited mainly conformably under dysoxic conditions. Deposition was controlled by two shallowing trends and occurred below, near and above mean storm- wave base. The contact of the top of the rst shallowing-upward trend in the succession is conformably, whereas the second shallowing-upward trend is truncated by an erosional unconformity, forming the top of the formation. An average sedimentation rate of c. 3.8 m/ Ma is estimated. The clay-mineral composition and illite crystallinity suggest a subsidence of approximately 5.7–6.3 km and a burial temperature of c. 280 °C. The low chlorite/kaolinite ratios indicate a mainly warm semi-humid climate setting at 35°–65° S, with sudden changes to a semi-arid setting. The subsidence, sedimentation rate and depositional environment suggest an Early Ordovician Avalonia-Gondwana separation

    Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

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    Cold-water corals (CWCs) constitute important deep-water ecosystems that are under increasing environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleorecords drilled through CWC mounds that reveal characteristic alterations between rapid formation and dormant or erosive phases. Previous studies have identified several central parameters for driving or inhibiting CWC growth such as food supply, oxygenation, and the carbon saturation state of bottom water, yet there are still large uncertainties about the relative importance of the different environmental parameters. To advance this debate we have performed a multiproxy study on a sediment core retrieved from the 25 m high Bowie Mound, located at 866 m water depth on the continental slope off southeastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multifactorial control on CWC growth at Bowie Mound during the past ∌ 160 kyr, which reveals distinct formation pulses during northern high-latitude glacial cold events (Heinrich stadials, HSs) largely associated with anomalously strong monsoonal rainfall over the continent. The ensuing enhanced runoff elevated the terrigenous nutrient and organic-matter supply to the continental margin and likely boosted marine productivity. The dispersal of food particles towards the CWC colonies during HSs was facilitated by the highly dynamic hydraulic conditions along the continental slope that prevailed throughout glacial periods. These conditions caused the emplacement of a pronounced nepheloid layer above Bowie Mound, thereby aiding the concentration and along-slope dispersal of organic matter. Our study thus emphasizes the impact of continental climate variability on a highly vulnerable deep-marine ecosystem

    Biostratigraphie et taxonomie des trilobites polymĂšres de la formation de Manuels River (Drumien, Cambrien moyen), Terre-Neuve, Canada

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    La formation cambrienne moyenne de Manuels River est renommĂ©e pour sa faune de trilobites bien prĂ©servĂ©s. Nous prĂ©sentons ici un assemblage nouvellement collectĂ© de 1184 spĂ©cimens provenant de la localitĂ© type de Conception Bay South, Terre-Neuve, Canada. L’assemblage faunique comprend des informations dĂ©taillĂ©es sur les aires de rĂ©partition prĂ©cises de chaque espĂšce. Ainsi, les zones de polymĂ©rides Paradoxides davidis et Paradoxides hicksi prĂ©cĂ©demment Ă©tablies pour la rĂ©gion et les zones d’agnostides Tomagnostus fissus, Hypagnostus parvifrons, Ptychagnostus atavus et Ptychagnostus punctuosus, reconnues mondialement, sont maintenant prĂ©cisĂ©ment corrĂ©lĂ©es. La faune de polymĂšres est comparable Ă  celle d’autres rĂ©gions d’Avalonia, de Baltica et partiellement du Gondwana. Notre analyse de l’assemblage faunique dĂ©montre qu’il est nĂ©cessaire de procĂ©der Ă  des rĂ©visions complĂštes des faunes de trilobites du Cambrien, y compris des taxons importants et bien connus comme Agraulos Hawle &amp; Corda, 1847 et Paradoxides sensu lato. Sao hirsuta Barrande, 1846 a Ă©tĂ© prĂ©cĂ©demment documentĂ© de la RĂ©publique TchĂšque, de l’Espagne et de l’Allemagne, et est maintenant dĂ©crit pour la premiĂšre fois de l’ouest d’Avalonia, tandis que Bailiella aequalis (Linnarsson, 1882) est dĂ©jĂ  mentionnĂ© pour l’est de Terre-Neuve et est maintenant illustrĂ© pour la premiĂšre fois. Les spĂ©cimens prĂ©sentĂ©s ici ont Ă©tĂ© assignĂ©s aux ordres Ptychopariida, Redlichiida et Corynexochida et comprennent Agraulos ceticephalus (Barrande, 1846); Jincella? applanata (Hicks dans Hicks &amp; Salter, 1869); Sao hirsuta Barrande, 1846; Bailiella aequalis (Linnarsson, 1882); Bailiella tenuicinta (Linnarsson, 1879); Meneviella venulosa (Hicks, 1872); Paradoxides davidis Salter, 1863; Plutonides hicksii (Salter,1866b); Clarella venusta (Billings, 1872); et Acontheus inarmatus Hutchinson, 1962.Newfoundland’s middle Cambrian fine-clastic Manuels River Formation is renowned for its well-preserved trilobite fauna. Here we present a newly collected assemblage of 1184 specimens from the type locality at Conception Bay South, Newfoundland, Canada. The faunal assemblage comprises detailed information about the accurate ranges of each species. Thus, the polymerid Paradoxides davidis and Paradoxides hicksi zones previously established for the region and the globally recognised agnostid Tomagnostus fissus, Hypagnostus parvifrons, Ptychagnostus atavus, and Ptychagnostus punctuosus zones are now precisely correlated. The polymerid fauna is comparable with that of other regions of Avalonia, Baltica, and partly with Gondwana. Our analysis of the faunal assemblage demonstrates that there is a need for comprehensive revisions of Cambrian trilobite faunas, including important and well-known taxa such as Agraulos Hawle &amp; Corda, 1847, and Paradoxides sensu lato. Sao hirsuta Barrande, 1846, was earlier documented from the Czech Republic, Spain and Germany, and is now first described from western Avalonia, while Bailiella aequalis (Linnarsson, 1882) was already mentioned for eastern Newfoundland and is now illustrated for the first time. The specimens presented here were assigned to the orders Ptychopariida, Redlichiida and Corynexochida and include Agraulos ceticephalus (Barrande, 1846); Jincella? applanata (Hicks in Salter &amp; Hicks, 1869); Sao hirsuta Barrande, 1846; Bailiella aequalis (Linnarsson, 1882); Bailiella tenuicinta (Linnarsson, 1879); Meneviella venulosa (Hicks, 1872); Paradoxides davidis Salter, 1863; Plutonides hicksii (Salter, 1866b); Clarella venusta (Billings, 1872); and Acontheus inarmatus Hutchinson, 1962.</p

    Biostratigraphy and taxonomy of Drumian (middle Cambrian) agnostid trilobites of the Manuels River Formation, Avalonian Newfoundland, Canada

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    New, accurately located and well‐preserved agnostid trilobite material has been collected from the type locality of the Drumian (middle Cambrian, Miaolingian) Manuels River Formation, Newfoundland, Canada. The well‐exposed grey to black shales containing the fauna were deposited on the former microcontinent Avalonia. Four interval zones for the succession are proposed, namely, the Tomagnostus fissus, Hypagnostus parvifrons, Ptychagnostus atavus and Ptychagnostus punctuosus zones. The Tomagnostus fissus and Ptychagnostus atavus zones are distinct from each other, which leads to a significantly shorter and stratigraphically higher Ptychagnostus atavus Zone compared with other sections (Scandinavia, South China, Utah and Nevada, Greenland). Specimens of Ptychagnostus atavus, however, occur abundantly, with 107 specimens identified in a short interval of the succession. The Ptychagnostus punctuosus Zone can be correlated globally. The faunal assemblage is comparable to that of Scandinavia, Greenland and England. Ptychagnostus affinis is recorded for the first time from Avalonia. The 1408 collected specimens were assigned to the suborders Agnostina and Eodiscina and to the families Peronopsidae and Ptychagnostidae, and Condylopygidae and Eodiscidae, respectively, with the following species: Peronopsis fallax (Linnarsson), Peronopsis scutalis (Hicks), Hypagnostus parvifrons (Linnarsson), Ptychagnostus punctuosus (Angelin), Ptychagnostus affinis (BrĂžgger), Ptychagnostus atavus (Tullberg), Tomagnostus fissus (Lundgren), Tomagnostus perrugatus (Grönwall), Pleuroctenium granulatum (Barrande) and Eodiscus punctatus (Salter).Klaus Tschira Stiftung http://dx.doi.org/10.13039/501100007316ODWIN gGmb

    FIG. 15 in Biostratigraphy and taxonomy of polymerid trilobites of the Manuels River Formation (Drumian, middle Cambrian), Newfoundland, Canada

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    FIG. 15. — Plutonides hicksii (Salter, 1866b): A, internal cast of a cranidium, occipital node preserved, with a vertical groove crossing the cranidium (NFM F-2781 from 4.52 m); B, internal cast of a cranidium with preserved exoskleleton (NFM F-3894 from 2.96 m); C, internal cast of a cranidium, occipital node and ornamentation on fixigenae preserved (NFM F-2861 from 2.53); D, internal cast of a cranidium, with a vertical groove crossing the cranidium (NFM F-3258 from 4.06 m). Scale bar: 3 mm.Published as part of Unger, Tanja, Hildenbrand, Anne, Stinnesbeck, Wolfgang & Austermann, Gregor, 2022, Biostratigraphy and taxonomy of polymerid trilobites of the Manuels River Formation (Drumian, middle Cambrian), Newfoundland, Canada, pp. 1051-1087 in Geodiversitas 44 (33) on page 1073, DOI: 10.5252/geodiversitas2022v44a33, http://zenodo.org/record/747765

    Quantifying the diagenetic impact in the late Ediacaran and Early Palaeozoic of the Avalon Peninsula using illite “crystallinity”

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    The Avalon Peninsula, Newfoundland, Canada, defined as the type zone of Avalonia is believed to have been impacted by several orogenetic and deformation events since the Neoproterozoic. Previous studies determined the lowest degree of metamorphism reached in the successions was of the prehnite-pumpellyite or greenschist facies. We sampled and measured thirteen clastic sedimentary sections ranging from the late Ediacaran to the Early Ordovician and analysed the illite “crystallinity” of 331 samples using the Kbler index. Our results show diagenetic zones occur related to lithology, age and burial depth, respectively, and regional setting. Samples adjacent to the fault zones bounding the Holyrood Horst experienced among the highest degree of metamorphism (anchizone) in the study area. The lowest degree of thermal alteration occurs in the high stratigraphic sections at the centre of the horst structure where shallow diagenetic conditions are preserved. Fault zones, most probably active during the Acadian Orogeny, may have served as potential paths for hot fluids in bounding areas of the horst, whereas the centre of the horst remained almost unaffected by any metamorphic overprint. The thermal impact decreases from the Bonavista Peninsula to the study area from greenschist facies to anchizonal and diagenetic. The study area experienced lower metamorphic conditions than major regions of Avalonia south of the study area on the mainland of New Brunswick and Maine and eastwards in Europe. The thermal impact is in part consistent with a few other areas of Avalonia, such as the Mira terrane and the Antigonish Highlands in Nova Scotia.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

    Sedimentological and geochemical data from cold water coral bearing Bowie Mound core M125-34-2 and off-mound core M125-50-3

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    This data set contains results of analyses performed on core M125-34-2 (retrieved during R/V METEOR Expeditin M125 in Spring 2016) from the cold water coral-bearing Bowie Mound, located off Cabo Frio, Eastern Brazil. Analyses were performed to determine the paleoenvironmental conditions that favored or prevented coral growth. The data comprises cold water coral contents and bioturbation index based on CT-scanning, benthic foraminiferal isotopes (C and O), 13C of organic material, sortable silt, elemental ratios based on XRF core-scanning, mineral content based on Rietveld refinement of XRD data, as well as bulk TOC content and Corganic/Ntotal ratios. For comparison an off-mound site (M125-50-3) was analyzed for benthic foraminiferal isotopes (C and O) and sortable silt
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