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  • 1. Betts, Marissa, J.
    et al.
    Paterson, John, R.
    Jago, James, B.
    Jacquet, Sarah, M.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Brock, Glenn, A.
    A new lower Cambrian shelly fossil biostratigraphy for South Australia2016In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 36, p. 163-195Article in journal (Refereed)
    Abstract [en]

    Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions stillawaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes are ultimately the key to resolving broader issues of global correlationwithin the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids. Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3–4. The Kulparina rostrata Zone (new) and part of the overlyingMicrina etheridgei Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 Dailyatia odyssei Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian–Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China.

  • 2. Betts, Marissa, J.
    et al.
    Paterson, John, R.
    Jago, James, B.
    Jacquet, Sarah, M.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Brock, Glenn, A.
    A new lower Cambrian shelly fossil biostratigraphy for South Australia:Reply2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 44, p. 262-264Article in journal (Refereed)
  • 3.
    Betts, Marissa, J.
    et al.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Paterson, John, R.
    Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia.
    Jago, James, B.
    School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
    Jacquet, Sarah, M.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK.
    Brock, Glenn, A.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Global correlation of the early Cambrian of South Australia: Shelly faunaof the Dailyatia odyssei Zone2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 46, p. 240-279Article in journal (Refereed)
    Abstract [en]

    A lack of well resolved biostratigraphic data has prevented robust regional and global correlation of lower Cambriansuccessions from South Australia. A new early Cambrian biostratigraphy, based on data derived from 21measured stratigraphic sections and drill cores (11 described herein) reveals the abundance and diversity ofshelly fauna from the Arrowie Basin, and the value of early Cambrian “small shelly fossils” (SSF) for biostratigraphicstudies. Here we examine shelly fauna associated with the youngest of three recently establishedbiozones, the Dailyatia odyssei Taxon Range Zone (hereafter D. odyssei Zone), and their correlative potential.The D. odyssei Zone features a diverse suite of tommotiids, organophosphatic brachiopods, bradoriid arthropods,molluscs and phosphatic problematica. This fauna permits strong correlation (often at species-level) with othermajor early Cambrian terranes, particularly Antarctica, South China and Laurentia, and suggest a Cambrian Series2, Stages 3–4 age for the D. odyssei Zone. Bradoriids have proven to be useful biostratigraphic tools. Four newspeciesand three new genera are described herein: Acutobalteus sinuosus gen. et sp. nov., Eozhexiella adnyamathanha gen. etsp. nov., Manawarra jonesi gen. et sp. nov. and Mongolitubulus descensus sp. nov. The description of Eohadrotreta sp.cf. zhenbaensis represents the first occurrence of the acrotretoid brachiopod Eohadrotreta from Australia.

  • 4.
    Betts, Marissa J.
    et al.
    Macquarie University, Sydney, Australia.
    Topper, Timothy P.
    Geological Museum, Copenhagen.
    Valentine, James L.
    Macquarie University, Sydney, Australia.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn A.
    Macquarie university, Australia.
    A new early Cambrian bradoriid (Arthropoda) assemblage from the northern Flinders Ranges, South Australia2014In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 25, p. 420-437Article in journal (Refereed)
    Abstract [en]

    A new assemblage of early Cambrian bivalved arthropods (Bradoriida) is described from the Arrowie Syncline in the northern Flinders Ranges, South Australia. The well preserved, largely endemic fauna comprises a total of six taxa (including five new species): Jiucunella phaseloa sp. nov., Jixinlingella daimonikoa sp. nov., Mongolitubulus anthelios sp. nov., Neokunmingella moroensis sp. nov., Phasoia cf. spicata ( Öpik, 1968), and Sinskolutella cuspidata sp. nov. This assemblage is derived from a carbonate sedimentary package representing a high energy, shallow water archaeocyath-Renalcis biohermal facies of Terreneuvian, Stage 2 age which transitions up-section to a more restricted, low energy, intra-shelf lagoonal environment that correlates with a Cambrian Series 2, Stage 3 age. The new taxon J. phaseloa sp. nov., has a first appearance datum (FAD) in shallow water biohermal facies of the Hideaway Well Member of the Wilkawillina Limestone at a level 47 m below the FAD of Pelagiella subangulata which is taken to approximate the base of Series 2, Stage 3 in South Australia. Along with Liangshanella circumbolina, this makes J. phaseloa sp. nov. amongst the oldest bivalved arthropods in South Australia and potentially greater Gondwana. The presence of 25 bradoriid taxa from the early Cambrian of South Australia suggests East Gondwana represents a major centre of origin for the Bradoriida.

  • 5. Eyal, Moshe
    et al.
    Be'eri-Shlevin, Yaron
    Eyal, Yehuda
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Litvinovsky, Boris
    Three successive Proterozoic island arcs in the Northern Arabian–Nubian Shield: Evidence from SIMS U–Pb dating of zircon2014In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 25, p. 338-357Article in journal (Refereed)
  • 6. Gardiner, Nicholas J.
    et al.
    Searle, Michael P.
    Morley, Christopher K.
    Robb, Laurence J.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Roberts, Nick M.W.
    Kirkland, Christopher L.
    Spencer, Christopher J.
    The crustal architecture of Myanmar imaged through zircon U-Pb, Lu-Hf and O isotopes: Tectonic and metallogenic implications2018In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 62, p. 27-60Article in journal (Refereed)
    Abstract [en]

    The Tethys margin in central and eastern Asia is comprised of continental terranesseparated by suture zones, some of which remain cryptic. Determining the crustal architecture, and therefore the geological history, of the Eastern Tethyan margin remains challenging. Sited in the heart of this region, Myanmar is a highly prospective but poorly explored minerals jurisdiction. A better understanding of Myanmar's mineralization can only be realized through a better understanding of its tectonic history, itself reflected in at least four major magmatic belts. The Eastern and the Main Range Provinces are associated with the Late Permian to Early Triassic closure of Palaeo-Tethys. The Mogok–Mandalay–Mergui Belt and Wuntho–Popa Arc are a response to the Eocene closure of Neo-Tethys. However, magmatic ages outside these two orogenic events are also recorded. We present new zirconU-Pb, Lu-Hf and O isotope data from magmatic rocks across Myanmar, which we append to the existing dataset to isotopically characterize Myanmar's magmatic belts. Eastern Province Permian I-type magmatism has evolved εHf (−10.9 to −6.4), whilst Main Range Province Triassic S-type magmatism also records evolved εHf (−13.5 to −8.8). The Mogok-Mandalay-Mergui Belt is here divided into the Tin Province and the Mogok Metamorphic Belt. The Tin Province hosts ca. 77–50 Ma magmatism with evolved εHf (−1.2 to −15.2), and δ18O of 5.6–8.3‰. The Mogok Metamorphic Belt exhibits a more complex magmatic and metamorphic history, and granitoids record Jurassic, Late Cretaceous, and Eocene to Miocene phases of magmatism, all of which exhibit evolved εHf values between −4.6 and −17.6, and δ18O between 6.3 and 9.2‰. From the Tagaung-Myitkyina Belt, we report a magmatic age of 172 Ma and εHf of 18.1 to 10.8. To accommodate the geological evidence, we propose a tectonic model for Myanmar involving a greater Sibumasu – where the documented zircon isotopic variations reflect compositional variations in magmatic source – and invoke the role of a Tengchong Block. The Baoshan Block and Greater Sibumasu were likely assembled on or before the Triassic, a former Andean margin and suture which may lie across the Northern Shan Plateau, and reflected in isotopic differences between the northern and southern parts of the Mogok Metamorphic Belt. This contiguous Sibumasu–Baoshan Block then sutured onto the Indochina margin in the Late Triassic. We propose that a Tengchong Block within Myanmar provides for a southerly termination of the Meso-Tethys suture immediately north of the Mogok area. A discrete Tengchong Block may explain a discontinuous arc of Late Triassic to Jurassic I-type magmatism in central Myanmar, representing an Andean-type margin sited above a subducting Meso-Tethys on the margin of Sibumasu. The Tengchong Block sutured onto Greater Sibumasu before the Late Cretaceous, after which subduction of Neo-Tethys drove the magmatism of the Wuntho-Popa Arc and ultimately that of the Tin Province. The metallogenic character of granite belts in Myanmar reflects the crustal architecture of the region, which is remarkable for its prolific endowment of granite-hosted Sn-W mineralization in two quite distinct granite belts related to sequential Indosinian and Himalayan orogenesis.

  • 7. Gardiner, N.J.
    et al.
    Searle, M.P.
    Morley, C.K.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Spencer, C.J.
    Robb, L.J.
    The closure of Palaeo-Tethys in Eastern Myanmar and Northern Thailand: New insights from zircon U–Pb and Hf isotope data.2016In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 39, p. 401-422Article in journal (Refereed)
    Abstract [en]

    Two of the major granite belts of Southeast Asia are the Main Range and Eastern Province. Together, these are interpreted to represent the magmatic expression of the closure of Palaeo-Tethys during Late Palaeozoic to Early Mesozoic times. Recent geochronological and geochemical work has better delineated these belts within Peninsular Malaysia, thereby providing important constraints on the timing of Palaeo-Tethys suturing. However, the northern extension of this Palaeo-Tethyan suture is less well understood. Here we present new ion microprobe U–Pb zircon age data from northern Thailand and eastern Myanmar. Measured ages of 219 and 220 Ma from the Kyaing Tong granite imply northern extension of the Main Range Province into eastern Myanmar. The Tachileik granite in far eastern Myanmar yields an age of 266 Ma, consistent with published Eastern Province ages, and this therefore constrains the northern extension of the Palaeo-Tethys suture in eastern Myanmar. We further discuss how this suture may extend northwards into Yunnan. A Late Cretaceous age (70 Ma) measured in Thailand represents later magmatic activity, and is similar to published magmatic ages from central Myanmar. This younger magmatism is interpreted to be related to the subduction of Neo-Tethys prior to India–Asia collision. Further, we present new laser ablation zircon Hf isotope data from eastern Myanmar which suggest that Palaeoproterozoic crust underlies both the Main Range and Eastern Province granites. Our εHf model age of ca. 1750 Ma from Sibumasu, the basement underlying eastern Myanmar, lies within the range of other model ages reported thus far for the Baoshan Block north in Yunnan, interpreted by some to be the northern extension of Sibumasu.

  • 8.
    McLoughlin, Stephen
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Martin, Sarah
    Geological Survey of Western Australia, Department of Mines and Petroleum.
    The record of Australian Jurassic plant-arthropod interactions2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 940-959Article in journal (Refereed)
    Abstract [en]

    A survey of Australian Jurassic plant fossil assemblages reveals examples of foliar andwood damage generated by terrestrial arthropods attributed to leaf-margin feeding, surface feeding, lamina hole feeding, galling, piercingand-sucking, leaf-mining, boring and oviposition. These types of damage are spread across a wide range of fern and gymnosperm taxa, but are particularly well represented on derived gymnosperm clades, such as Pentoxylales and Bennettitales. Several Australian Jurassic plants show morphological adaptations in the form of minute marginal and apical spines on leaves and bracts, and scales on rachises that likely represent physical defences against arthropod herbivory. Only two entomofaunal assemblages are presently known from the Australian Jurassic but these reveal a moderate range of taxa, particularly among the Orthoptera, Coleoptera, Hemiptera and Odonata, all of which are candidates for the dominant feeding traits evidenced by the fossil leaf and axis damage. The survey reveals that plant–arthropod interactions in the Jurassic at middle to high southern latitudes of southeastern Gondwana incorporated a similar diversity of feeding strategies to those represented in coeval communities from other provinces. Further, the range of arthropod damage types is similar between Late Triassic and Jurassic assemblages from Gondwana despite substantial differences in the major plant taxa, implying that terrestrial invertebrate herbivoreswere able to successfully transfer to alternative plant hosts during the floristic turnovers at the Triassic–Jurassic transition.

  • 9. Pan, Bing
    et al.
    Brock, Glenn, A.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Betts, Marissa, J.
    Topper, Timothy, P.
    Li, Guoxiang
    Paterimitra pyramidalis Laurie, 1986, the first tommotiid discovered from the early Cambrian of North China2018In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 63, p. 179-185Article in journal (Refereed)
    Abstract [en]

    The eccentrothecimorph tommotiid Paterimitra pyramidalis Laurie, 1986, was previously only known from lower Cambrian rocks of the Northern Territory and South Australia. Herein, we document the first occurrence of P. pyramidalis from the Xinji Formation in the Shuiyu section at Ruicheng County, Shanxi Province, located at the southwestern margin of the North China Platform. This represents the first report of a tommotiid taxon from lower Cambrian strata of the North China Platform. All three sclerite types that characterise the scleritome of P. pyramidalis have been recovered and are described, permitting definitive identification to species level. The discovery of P. pyramidalis fromthe North China Platformnot only greatly extends the palaeogeographic range of this distinctive tommotiid taxon, but also supports planktotrophic development of larvae in Paterimitra as a stem group brachiopod. The discovery of P. pyramidalis supports a Cambrian, Epoch 2, late Age 3 to early Age 4 age for the shelly fossil fauna from the Xinji Formation and indicates a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian.

  • 10.
    Schneebeli-Hermann, Elke
    et al.
    Palaeoecology, Institute of Environmental Biology, Faculty of Science, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands.
    Kürschner, Wolfram
    Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, N-0316 Oslo, Norway.
    Kerp, Hans
    Forschungsstelle für Paläobotanik am Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität Münster, Hindenburgplatz 57, 48143 Münster, Germany.
    Bomfleur, Benjamin
    Swedish Museum of Natural History, Department of Paleobiology.
    Hochuli, Peter
    Institute and Museum of Palaeontology, University of Zurich, Karl Schmid-Str. 4, CH-8006 Zurich, Switzerland.
    Bucher, Hugo
    Institute and Museum of Palaeontology, University of Zurich, Karl Schmid-Str. 4, CH-8006 Zurich, Switzerland.
    Ware, David
    Institute and Museum of Palaeontology, University of Zurich, Karl Schmid-Str. 4, CH-8006 Zurich, Switzerland.
    Roohi, Ghazala
    Pakistan Museum of Natural History, Garden Avenue, Islamabad 44000, Pakistan.
    Vegetation history across the Permian–Triassic boundary in Pakistan (Amb section, Salt Range)2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 911-924Article in journal (Refereed)
    Abstract [en]

    Hypotheses about the Permian–Triassic floral turnover range from a catastrophic extinction of terrestrial plant communities to a gradual change in floral composition punctuated by intervals indicating dramatic changes in the plant communities. The shallow marine Permian–Triassic succession in the Amb Valley, Salt Range, Pakistan, yields palynological suites together with well-preserved cuticle fragments in a stratigraphically well-constrained succession across the Permian–Triassic boundary. Palynology and cuticle analysis indicate a mixed GlossopterisDicroidium flora in the Late Permian. For the first time Dicroidium cuticles are documented from age-constrained Upper Permian deposits on the Indian subcontinent. Close to the Permian–Triassic boundary, several sporomorph taxa disappear. However, more than half of these taxa reappear in the overlying Smithian to Spathian succession. The major floral change occurs towards the Dienerian. From the Permian–Triassic boundary up to the middle Dienerian a gradual increase of lycopod spore abundance and a decrease in pteridosperms and conifers are evident. Synchronously, the generic richness of sporomorphs decreases. The middle Dienerian assemblages resemble the previously described spore spikes observed at the end-Permian (Norway) and in the middle Smithian (Pakistan) and might reflect a similar ecological crisis.

  • 11.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn A.
    Macquarie University.
    First occurrence of a new Ocruranus-like helcionelloid mollusc from the lower Cambrian of East Gondwana2012In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 22, p. 256-261Article in journal (Refereed)
    Abstract [en]

    A new cap-shaped mollusc, Emargimantus angulatus gen. et sp. nov. is described from the Arrowie Basin of South Australia. The new species is closely comparable to mollusc species from South China and North-East Greenland previously described under the generic name Ocruranus Liu, a genus recently reinterpreted as a multiplated, possibly polyplacophoran mollusc. Emargimantus is interpreted as a univalved helcionelloid mollusc and differs from Ocruranus in both morphology and function. E. angulatus represents the first discovery of Ocruranus-like helcionelloids in the lower Cambrian of eastern Gondwana and demonstrates that these molluscs had a global distribution during the early Cambrian.

  • 12.
    Slater, Ben
    et al.
    School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
    McLoughlin, Stephen
    Swedish Museum of Natural History, Department of Paleobiology.
    Hilton, Jason
    School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
    A high-latitude Gondwanan lagerstätte: The Permian permineralised peat biota of the Prince Charles Mountains, Antarctica2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 1446-1473Article in journal (Refereed)
    Abstract [en]

    The Toploje Member chert is a Roadian to Wordian autochthonous–parautochthonous silicified peat preserved within the Lambert Graben, East Antarctica. It preserves a remarkable sample of terrestrial life from highlatitude central Gondwana prior to the Capitanian mass extinction event from both mega- and microfossil evidence that includes cryptic components rarely seen in other fossil assemblages. The peat layer is dominated by glossopterid and cordaitalean gymnosperms and containsmoderately common herbaceous lycophytes, together with a broad array of dispersed organs of ferns and other gymnosperms. Rare arthropod–plant and fungal–plant interactions are preserved in detail, together with a plethora of fungal morphotypes, Peronosporomycetes, arthropod remains and a diverse coprolite assemblage. Comparisons to other Palaeozoic ecosystems show that the macro flora is of low diversity. The fungal and invertebrate–plant associations demonstrate that a multitude of ecological interactions were well developed by the Middle Permian in high-latitude forest mires that contributed to the dominant coal deposits of the Southern Hemisphere. Quantitative analysis of the constituents of the silicified peat and of macerals within adjacent coal seams reveals that whilst silicified peats provide an unparalleled sample of the organisms forming Permian coals, they do not necessarily reflect the volumetric proportions of constituents within the derived coal. The Toploje Member chert Lagerstätte provides a snapshot of a rapidly entombed mire climax ecosystem in the closing stages of the Palaeozoic, but prior to the onset of the protracted crisis that engulfed and overthrew these ecosystems at the close of the Permian.

  • 13. Steinthorsdottir, Margret
    et al.
    Vajda, Vivi
    Swedish Museum of Natural History, Department of Paleobiology. Department of Geology, Lund University, Sweden.
    Early Jurassic (late Pliensbachian) CO2 concentrations based on stomatalanalysis of fossil conifer leaves from eastern Australia2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 932-939Article in journal (Refereed)
    Abstract [en]

    The stomatal index (a measure of stomatal density) of an extinct Australian Early Jurassic araucariacean conifer species, Allocladus helgei Jansson, is used to reconstruct the atmospheric carbon dioxide concentration (pCO2) in the Early Jurassic. The fossil leaves are preserved in a single bed, palynologically dated to late Pliensbachian (~185–183 Mya). Atmospheric pCO2 is estimated from the ratios between the stomatal index of A. helgei and the stomatal indices of three modern analogs (nearest living equivalent plants). CO2 concentration in the range of ~750–975 ppm was calibrated from the fossil material, with a best-estimated mean of ~900 ppm. The new average pCO2 determined for the late Pliensbachian is thus similar to, although ~10% lower, than previously inferred minimum concentrations of ~1000, based on data from the Northern Hemisphere, but may help constrain pCO2 during this period. Our results are the first pCO2 estimates produced using Jurassic leaves from the Southern Hemisphere and showthat i) paleo-atmospheric pCO2 estimates are consistent at a global scale, though more investigations of Southern Hemisphere material are required, and ii) the stomatal proxy method can now be used without the context of relative change in pCO2 when applying the correct methodology.

  • 14.
    Tosolini, Anne-Marie
    et al.
    School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia.
    McLoughlin, Stephen
    Swedish Museum of Natural History, Department of Paleobiology.
    Wagstaff, Barbara
    School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia.
    Cantrill, David
    National Herbarium of Victoria, Royal Botanic Gardens Melbourne, South Yarra, Victoria 3141, Australia.
    Galagher, Stephen
    School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia.
    Cheirolepidiacean foliage and pollen from Cretaceous high-latitudes of southeastern Australia2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 960-977Article in journal (Refereed)
    Abstract [en]

    Cheirolepidiaceae leaves and pollen are recorded from Valanginian–Albian strata of southeastern Australia that were deposited at high-latitudes under cool, moist climates in contrast to the semi-arid or coastal habitats preferred by many northern Gondwanan and Laurasian representatives of this group. Leaves of this family are characterized by thick cuticles and cyclocytic stomata with randomly oriented apertures, arranged in scattered or longitudinal rows or bands. Stomata are deeply sunken and surrounded by four to six subsidiary cells that bear one or two ranks of prominent overarching papillae, which may constrict the mouth of the pit. Three new taxa (Otwayia denticulata Tosolini, Cheirolepidiaceae cuticle sp. A and sp. B) are distinguished based on cuticular features, adding to several previously documented cheirolepid conifers in the Early Cretaceous of eastern Australia. Cheirolepidiaceae foliage is preserved predominantly in fluvial floodbasin settings and is interpreted to be derived from small trees occupying disturbed or low-nutrient sites. The foliage is associated with Classopollis/Corollina pollen and roots characterized by prominent mycorrhizal nodules. A Cenomanian Classopollis type recognised from Bathurst Island, Northern Australia, is recorded for the first time from the Early Cretaceous Eumeralla Formation, Otway Basin. Classopollis locally is rare in Valanginian–Barremian strata of Boola Boola, Gippsland, but constitutes up to 14% of the palynomorph assemblage in Albian strata. This indicates that the family was locally abundant in cool southern high-latitude climates of the Mesozoic, contrary to previous reports of its rarity in this region.

  • 15.
    Vajda, Vivi
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Ocampo, Adriana
    NASA Headquaters, Washington.
    Ferrow, Embaie
    Department of Geology, Lund University.
    Bender Koch, Christian
    Department of Chemistry, University of Copenhagen.
    Nano particles as the primary cause for long-termsunlight suppression athigh southern latitudes following the Chicxulub impact — evidence fromejecta deposits in Belize and Mexico2015In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 27, p. 1079-1088Article in journal (Refereed)
    Abstract [en]

    Life on Earth was sharply disrupted 66 Ma ago as an asteroid hit the sea-floor inwhat is today Yucatan Peninsula, Mexico. Approximately 600 km3 of sedimentary rock were vapourized, ejected into the atmosphere and subsequently deposited globally as an ejecta apron and fallout layer. Proximal ejecta deposits occur in Belize and southern Mexico where the so called Albion Island spheroid bed is superimposed on the target rock (the Barton Creek Formation). We analysed the spheroid bed via Mössbauer spectroscopy, petrology, XRD, and palynology at several sites ~350–500 km distance from the crater centre. Our results show that the relative concentrations of Fe in nano-phase goethite (α-FeOOH) are very high in the spheroid bed samples from Albion Island (Belize) and from Ramonal South (Mexico), but are low to absent in the spheroid bed at Ramonal North, and in the Cretaceous target rock. Moreover, our study shows that goethite and haematite are the dominant Fe-oxide nano-phases and the XRD results show that the target rock consists of both calcite and dolomite. We suggest that the heterogeneous composition of the spheroid bed between the various sites reflects the different types of target rocks that were dispersed within the rapidly expanding vapour plume and the complex sorting processes involved in the formation of the ejecta blanket. The distribution of the vapourized target rock strongly influenced life on Earth at the close of the Mesozoic. However, the comparatively thin K–Pg boundary clay in high-latitude Gondwanan successions combined with evidence of catastrophic changes to the biota in this region implies that the long-term sunlight suppression in the Southern Hemisphere was mainly governed by the large quantities of hydrous aerosols nucleated around sulphuric acid droplets or nano-sized particles, such as the nano-phase Fe-oxides.

  • 16.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Pidgeon, R.T. (Contributor)
    What can Hadean detrital zircon really tell us? A critical evaluation of their geochronology with implications for the interpretation of oxygen and hafnium isotopes2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 51, p. 78-91Article in journal (Refereed)
    Abstract [en]

    Rare Hadean zircon grains represent the only direct sample of the Earth older than 4.0 Ga. As such, they have tremendous potential to illuminate our knowledge of this period of Earth's history for which there is no extant rock record. In this study we revisit the existing dataset, supplemented by new analyses, to identify those grains from which a robust age may be inferred. This rigorous filtering approach identifies four distinct zircon growth events in the Hadean between ca. 4.4 Ga and 4.0 Ga, and allows a reassessment of conclusions made from the determination of the O- and Hf-isotope systematics in these grains. Notably, we find no firm evidence for involvement of supracrustal reservoirs in zircon genesis prior to 4.15 Ga and, while our filtered Hf-isotope data support interpretations for a mafic protocrust, there are insufficient analyses to constrain its evolution accurately. Clearly, further work is required and needs to be conducted in a systematic manner that first seeks to establish both the age and homogeneity of any given grain before proceeding to other types of analysis.

  • 17.
    Whitehouse, Martin J.
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Nemchin, A. A.
    Pidgeon, R. T.
    What can Hadean detrital zircon really tell us?: A critical evaluation of their geochronology with implications for the interpretation of oxygen and hafnium isotopes2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 51, no Supplement C, p. 78-91Article in journal (Refereed)
    Abstract [en]

    Abstract Rare Hadean zircon grains represent the only direct sample of the Earth older than 4.0Ga. As such, they have tremendous potential to illuminate our knowledge of this period of Earth's history for which there is no extant rock record. In this study we revisit the existing dataset, supplemented by new analyses, to identify those grains from which a robust age may be inferred. This rigorous filtering approach identifies four distinct zircon growth events in the Hadean between ca. 4.4Ga and 4.0Ga, and allows a reassessment of conclusions made from the determination of the O- and Hf-isotope systematics in these grains. Notably, we find no firm evidence for involvement of supracrustal reservoirs in zircon genesis prior to 4.15Ga and, while our filtered Hf-isotope data support interpretations for a mafic protocrust, there are insufficient analyses to constrain its evolution accurately. Clearly, further work is required and needs to be conducted in a systematic manner that first seeks to establish both the age and homogeneity of any given grain before proceeding to other types of analysis.

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