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  • 1
    Online Resource
    Online Resource
    Chemotrophy-based phosphatic microstromatolites from the Mississippian at Drewer, Rhenish Massif, Germany
    Cambridge University Press (CUP) ; 2023
    In:  Geological Magazine
    Details
    In: Geological Magazine, Cambridge University Press (CUP)
    Abstract: The Drewer quarry located in the Rhenish Massif is a well-studied outcrop that comprises Upper Devonian (Famennian) to Lower Carboniferous (Viséan) strata. Within the Drewer deposits two black shale intervals have been described that are linked to two global oceanic anoxic events, the Hangenberg Event and the Lower Alum Shale Event. The black shales associated with the Middle Tournaisian Lower Alum Shale Event contain abundant phosphatic concretions, which were investigated using thin section petrography, powder X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The concretions formed during several growth phases under anoxic and at least episodically sulphidic conditions within the sediment and served as a substrate for subsurface microbial mats that formed phosphatic microstromatolites. The microstromatolites occur either as partially branched columns of up to 600 µm in length attached to the phosphatic concretions or as smaller, bulbous aggregates surrounding the concretions. Element mapping identified the presence of pyrite and other metal sulphides within the phosphatic microstromatolites. The carbon and oxygen stable isotopic composition of phosphate-associated carbonate within the phosphatic microstromatolites suggests that the mat-forming microorganisms were probably anaerobic, chemotrophic microbial communities dwelling in the anoxic environment during the Lower Alum Shale Event. Such interpretation agrees with the deeper-water depositional setting of the Lower Alum Black Shale and its high content of organic matter, suggesting that chemotrophic microbial mats are potent agents of phosphogenesis in general, and of the formation of phosphatic stromatolites in particular.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756823000493
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2023
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    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 2
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    Online Resource
    The environmental factors limiting the distribution of shallow-water terebratulid brachiopods
    Cambridge University Press (CUP) ; 2020
    In:  Paleobiology Vol. 46, No. 2 ( 2020-05), p. 193-217
    Details
    In: Paleobiology, Cambridge University Press (CUP), Vol. 46, No. 2 ( 2020-05), p. 193-217
    Abstract: The Cenozoic genus Terebratula seems to be an exception to the post-Permian trend in brachiopod retreat to offshore habitats, because it was species rich and numerically abundant in warm-temperate shallow-water environments in the Mediterranean and the Paratethys realms. This was so despite the general dominance of bivalves and the pervasive bioturbation and predation pressure during the Neogene. Terebratula , however, went extinct in the Calabrian (Pleistocene). The optimal environmental conditions for Terebratula during its prime are poorly known. The Águilas Basin (SE Spain) is an ideal study area to investigate the habitat of Terebratula , because shell beds of this brachiopod occur there cyclically in early Pliocene deposits. We evaluate the paleoecological boundary conditions controlling the distribution of Terebratula by estimating its environmental tolerances using benthic and planktic foraminiferal and nannoplanktic assemblages and oxygen isotopes of the secondary layer brachiopod calcite. Our results suggest that Terebratula in the Águilas Basin favored oligotrophic to mesotrophic, well-oxygenated environments at water depths of 60–90 m. Planktic foraminiferal assemblages and oxygen isotopes point to sea-surface temperatures between ~16°C and 22°C, and bottom-water temperatures between 17°C and 24°C. The analyzed proxies indicate that Terebratula tolerated local variations in water depth, bottom temperature, oxygenation, productivity, and organic enrichment. Terebratula was probably excluded by grazing pressure from well-lit environments and preferentially occupied sediment-starved, current-swept upper offshore habitats where coralline red algae were absent. Narrow temperature ranges of Terebratula species might have been a disadvantage during the high-amplitude seawater temperature fluctuations that started about 1 Ma, when the genus went extinct.
    Type of Medium: Online Resource
    ISSN: 0094-8373 , 1938-5331
    URL: Article
    DOI: 10.1017/pab.2020.11
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2052186-8
    SSG: 12
    SSG: 13
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  • 3
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    Online Resource
    Oxygen isotopes of bovid teeth as archives of paleoclimatic variations in archaeological deposits of the Ganga plain, India
    Cambridge University Press (CUP) ; 2004
    In:  Quaternary Research Vol. 62, No. 1 ( 2004-07), p. 19-28
    Details
    In: Quaternary Research, Cambridge University Press (CUP), Vol. 62, No. 1 ( 2004-07), p. 19-28
    Abstract: Oxygen isotope analysis was performed on enamel phosphate of mammalian teeth from archaeological sites Kalli Pachchhim and Dadupur in the central Ganga plain and Charda in the northern Ganga plain. The bulk oxygen isotopic compositions of enamel phosphate from third molars (M3) of Bos indicus individuals belonging to different cultural periods were used to understand the climatic changes during the past 3600 cal yr B.P. Oxygen isotope ratios indicate humid conditions around 3600 cal yr B.P., followed by a trend toward drier conditions until around 2800 cal yr B.P. Then from 2500 to 1500 cal yr B.P. there is a trend toward higher humidity, followed by the onset of a dry period around 1300 cal yr B.P. The study of intratooth δ 18 O variations in teeth from different periods demonstrates that the monsoon seasonality was prominent. Spatial changes in the amount of annual rainfall are also reflected in the δ 18 O values. Teeth derived from areas with intense rainfall have lighter isotope ratios compared to teeth from regions receiving less rain, but they show similar seasonal patterns. The long-term paleoclimatic variations reflected by fluctuations in bulk δ 18 O p values from M3 teeth match well with the regional paleoenvironmental records and show a good correlation to the cultural changes that took place during this time span in Ganga plain.
    Type of Medium: Online Resource
    ISSN: 0033-5894 , 1096-0287
    URL: Article
    DOI: 10.1016/j.yqres.2004.03.003
    RVK:
    RA 1000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2004
    detail.hit.zdb_id: 1471589-2
    detail.hit.zdb_id: 205711-6
    SSG: 13
    SSG: 14
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  • 4
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    Online Resource
    Carbon isotope chemostratigraphy and sea-level history of the Hirnantian Stage (uppermost Ordovician) in the Oslo–Asker district, Norway
    Cambridge University Press (CUP) ; 2021
    In:  Geological Magazine Vol. 158, No. 11 ( 2021-11), p. 1977-2008
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 158, No. 11 ( 2021-11), p. 1977-2008
    Abstract: We present a δ 13 C carb chemostratigraphy for the Late Ordovician Hirnantian Stage based on 208 whole-rock samples from six outcrops in the Oslo–Asker district, southern Norway. Our data include the Norwegian type section for the Hirnantian Stage and Ordovician–Silurian boundary at Hovedøya Island. The most complete record of the Hirnantian Isotope Carbon Excursion (HICE) is identified in a coastal exposure at Konglungø locality where the preserved part of the anomaly spans a c. 24 m thick, mixed carbonate–siliciclastic succession belonging to the upper Husbergøya, Langåra and Langøyene formations and where δ 13 C carb peak values reach c. +6 ‰. Almost the entire HICE occurs above beds containing the Hirnantia Fauna, suggesting a latest Hirnantian age for the peak of the excursion. The temporal development of the HICE in southern Norway is associated with substantial shallowing of depositional environments. Sedimentary facies and erosional unconformities suggest four inferably fourth-order glacio-eustatically controlled sea-level lowstands with successively increased exposure and erosion to the succession. The youngest erosional unconformity is related to the development of incised valleys and resulted in cut-out of at least the falling limb of the HICE throughout most of the Oslo–Asker district. The fill of the valleys contains the falling limb of the HICE, and the postglacial transgression therefore can be assigned to the latest part of the Hirnantian Age. We address the recent findings of the chitinozoan Belonechitina gamachiana in the study area and its relationship to the first occurrence of Hirnantia Fauna in the studied sections, challenging identification of the base of the Hirnantian Stage.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756821000546
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
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    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 5
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    Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland
    Cambridge University Press (CUP) ; 2018
    In:  Geological Magazine Vol. 155, No. 4 ( 2018-05), p. 865-877
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 155, No. 4 ( 2018-05), p. 865-877
    Abstract: Globally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756816000947
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
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  • 6
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    Online Resource
    Integrated Cambrian biostratigraphy and carbon isotope chemostratigraphy of the Grönhögen-2015 drill core, Öland, Sweden
    Cambridge University Press (CUP) ; 2019
    In:  Geological Magazine Vol. 156, No. 06 ( 2019-06), p. 935-949
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 156, No. 06 ( 2019-06), p. 935-949
    Abstract: The Grönhögen-2015 core drilling on southern Öland, Sweden, penetrated 50.15 m of Cambrian Series 3, Furongian and Lower–Middle Ordovician strata. The Cambrian succession includes the Äleklinta Member (upper Stage 5) of the Borgholm Formation and the Alum Shale Formation (Guzhangian–Tremadocian). Agnostoids and trilobites allowed subdivision of the succession into eight biozones, in ascending order: the uppermost Cambrian Series 3 (Guzhangian) Agnostus pisiformis Zone and the Furongian Olenus gibbosus , O. truncatus , Parabolina spinulosa , Sphaerophthalmus ? flagellifer , Ctenopyge tumida , C. linnarssoni and Parabolina lobata zones. Conspicuous lithologic unconformities and the biostratigraphy show that the succession is incomplete and that there are several substantial gaps of variable magnitudes. Carbon isotope analyses (δ 13 C org ) through the Alum Shale Formation revealed two globally significant excursions: the Steptoean Positive Carbon Isotope Excursion (SPICE) in the lower–middle Paibian Stage, and the negative Top of Cambrian Excursion (TOCE), previously referred to as the HERB Event, in Stage 10. The δ 13 C org chemostratigraphy is tied directly to the biostratigraphy and used for an improved integration of these excursions with the standard agnostoid and trilobite zonation of Scandinavia. Their relations to that of coeval successions in Baltoscandia and elsewhere are discussed. The maximum amplitudes of the SPICE and TOCE in the Grönhögen succession are comparable to those recorded in drill cores retrieved from Scania, southern Sweden. The results of this study will be useful for assessing biostratigraphic relations between shale successions and carbonate facies on a global scale.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756818000298
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 7
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    Online Resource
    Ultra-shallow-marine anoxia in an Early Triassic shallow-marine clastic ramp (Spitsbergen) and the suppression of benthic radiation
    Cambridge University Press (CUP) ; 2016
    In:  Geological Magazine Vol. 153, No. 2 ( 2016-03), p. 316-331
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 153, No. 2 ( 2016-03), p. 316-331
    Abstract: Lower Triassic marine strata in Spitsbergen accumulated on a mid-to-high latitude ramp in which high-energy foreshore and shoreface facies passed offshore into sheet sandstones of probable hyperpycnite origin. More distal facies include siltstones, shales and dolomitic limestones. Carbon isotope chemostratigraphy comparison allows improved age dating of the Boreal sections and shows a significant hiatus in the upper Spathian. Two major deepening events, in earliest Griesbachian and late Smithian time, are separated by shallowing-upwards trends that culminated in the Dienerian and Spathian substages. The redox record, revealed by changes in bioturbation, palaeoecology, pyrite framboid content and trace metal concentrations, shows anoxic phases alternating with intervals of better ventilation. Only Dienerian–early Smithian time witnessed persistent oxygenation that was sufficient to support a diverse benthic community. The most intensely anoxic, usually euxinic, conditions are best developed in offshore settings, but at times euxinia also developed in upper offshore settings where it is even recorded in hyperpycnite and storm-origin sandstone beds: an extraordinary facet of Spitsbergen's record. The euxinic phases do not track relative water depth changes. For example, the continuous shallowing upwards from the Griesbachian to lower Dienerian was witness to several euxinic phases separated by intervals of more oxic, bioturbated sediments. It is likely that the euxinia was controlled by climatic oscillations rather than intra-basinal factors. It remains to be seen if all the anoxic phases found in Spitsbergen are seen elsewhere, although the wide spread of anoxic facies in the Smithian/Spathian boundary interval is clearly a global event.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756815000588
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2016
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
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