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  • 1. Brosse, Morgane
    et al.
    Bucher, Hugo
    Bagherpour, Borhan
    Baud, Aymon
    Frisk, Åsa M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Guodun, Kuang
    Goudemand, Nicolas
    Conodonts from the Early Triassic Microbialite of Guangxi (South China): Implications for the Definition of the Base of the Triassic System2015In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 58, no 3, p. 563-584Article in journal (Refereed)
    Abstract [en]

    We describe a new Early Triassic (Griesbachian) succession of conodont faunas from a high-resolution sampling of the basal Early Triassic microbial limestone and the base of the overlying unit at the Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). The microbial limestone records the earliest phase of the Early Triassic biotic recovery after the end-Permian mass extinction. For the first time, rich conodont faunas are reported from within the microbialite. The faunas from Wuzhuan are largely dominated by anchignathodontids, including several Isarcicella species, which were previously documented only from strata above the microbialite. A total of 14 conodont species assigned to three genera is recorded from the Wuzhuan section. Starting from the base of the microbialite upwards, several species are sequentially added to the conodont assemblage. The alpha diversity peaks at the top of the microbialite. The conodont record in the considered microbialite interval at Wuzhuan is presumably unaffected by local ecological changes. It therefore more likely represents an evolutionary rather than an ecological pattern. We compare the Wuzhuan's conodont record with a well-supported phylogenetic model and suggest that the sequence of first occurrences at Wuzhuan is the closest to the true' sequence of evolutionary events that took place during this Griesbachian radiation of anchignathodontids. Based on comparisons with the GSSP section at Meishan, we suggest further that the first occurrence of Hindeodus parvus in Meishan does not correspond to its first appearance datum.

  • 2.
    Brosse, Morgane
    et al.
    Univ Zurich, Palaontol Inst & Museum, Karl Schmid Str 4, CH-8006 Zurich, Switzerland.
    Bucher, Hugo
    Univ Zurich, Palaontol Inst & Museum, Karl Schmid Str 4, CH-8006 Zurich, Switzerland.
    Baud, Aymon
    BGC, Parc Rouvraie 28, CH-1018 Lausanne, Switzerland.
    Frisk, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Goudemand, Nicolas
    Univ Claude Bernard Lyon 1, Univ Lyon, Inst Genom Fonct Lyon, ENS Lyon,CNRS,UMR 5242, 46 Allee Italie, F-69364 Lyon 07, France.
    Hagdorn, Hans
    Muschelkalkmuseum, Schlossstr 11, D-74653 Ingelfingen, Germany.
    Nützel, Alexander
    LMU, Dept Earth & Environm Sci, SNSB Bayer Staatssammlung Palaontol & Geol, GeoBio Ctr,Palaeontol & Geobiol, Richard Wagner Str 10, D-80333 Munich, Germany.
    Ware, David
    Leibniz Inst Evolut & Biodiversitatsforsch, Museum Nat Kunde, Invalidenstr 43, D-10115 Berlin, Germany.
    Hautmann, Michael
    Univ Zurich, Palaontol Inst & Museum, Karl Schmid Str 4, CH-8006 Zurich, Switzerland.
    New data from Oman indicate benthic high biomass productivity coupled with low taxonomic diversity in the aftermath of the Permian-Triassic Boundary mass extinction2019In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 52, no 2, p. 165-187Article in journal (Refereed)
    Abstract [en]

    A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daffah conglomerate in eastern Oman (Batain), which provides new insights into the ecology and diversity during the early aftermath of the Permian-Triassic Boundary mass extinction. Based on conodont quantitative biochronology, we assign a middle Griesbachian age to the upper part of this boulder. It was derived from an offshore seamount and yielded both nektonic and benthic faunas, including conodonts, ammonoids, gastropods and crinoid ossicles in mass abundance. This demonstrates that despite the stratigraphically near extinction at the Permian-Triassic Boundary, Crinoidea produced enough biomass to form crinoidal limestone as early as middle Griesbachian time. Baudicrinus, previously placed in Dadocrinidae, is now placed in Holocrinidae; therefore, Dadocrinidae are absent in the Early Triassic, and Holocrinidae remains the most basal crown-group articulates, originating during the middle Griesbachian in the Tethyan Realm. Abundant gastropods assigned to Naticopsis reached a shell size larger than 20 mm and provide another example against any generalized Lilliput effect during the Griesbachian. Whereas the benthic biomass was as high as to allow the resumption of small carbonate factories, the taxonomic diversity of the benthos remained low compared to post-Early Triassic times. This slow benthic taxonomic recovery is here attributed to low competition within impoverished post-extinction faunas.

  • 3.
    Ebbestad, Jan Ove R.
    et al.
    Uppsala University, Music and Museums, Museum of Evolution.
    Hogstrom, Anette E. S.
    Frisk, Åsa M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Martma, Tonu
    Kaljo, Dimitri
    Kroger, Bjorn
    Parnaste, Helje
    Terminal Ordovician stratigraphy of the Siljan district, Sweden2015In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 137, no 1, p. 36-56Article, review/survey (Refereed)
    Abstract [en]

    Integration of new isotopic data and earlier biostratigraphic information from eight sections through the terminal Ordovician (Pirgu and Porkuni stages) of the Siljan district, Sweden, allows a more precise correlation of sections in terms of biostratigraphy and carbon isotope dating. Four levels with positive delta C-13 excursions are identified (from bottom) - the Moe, an unnamed excursion, Paroveja and Hirnantian Carbon Isotope Excursion (HICE). The delta C-13 values through the Boda Limestone are 1-2 parts per thousand higher than usual in Baltica, only the values for the HICE remains within what is expected. Background values increase from 1.5 parts per thousand in the bottom of the core of the Boda Limestone up to 3 parts per thousand in the top of it. The HICE is identified in five of eight sections and the main peak falls according to inferred correlation within the Metabolograptus persculptus Biozone, at or close to the Hindella beds in the Upper Boda Member. The late Katian (Pirgu) age of Holorhynchus in the Siljan district is clear and its co-occurrence with the chitinozoan Belonechitina gamachiana in Estonia supports a Katian age for this zone. The base of the Ozarkodina hassi Biozone may occur within units B-C of the Upper Boda Member and in the upper part of the Loka Formation and most likely is correlated with the M. persculptus Biozone. The Hirnantia-Dalmanitina faunas reported from the lowermost part of the Loka Formation and units B-D of the Upper Boda Member seem to range through all the Hirnantian, but detailed morphological studies allow to distinguish an older (=extraordinarius) and a younger (=persculptus) fauna.

  • 4.
    Ebbestad, Jan Ove R.
    et al.
    Uppsala University, Music and Museums, Museum of Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Högström, Anette
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Frisk, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Gastropods and tergomyans from the Upper Ordovician (Viru–Harju) of the Fågelsång area, Scania, southern Sweden2013In: Journal of Systematic Palaeontology, ISSN 1477-2019, E-ISSN 1478-0941, Vol. 11, no 3, p. 295-336Article in journal (Refereed)
    Abstract [en]

    A diverse tergomyan and gastropod assemblage is described from the Global Boundary Stratotype Section and Point (GSSP)section of the Sandbian Stage, Upper Ordovician, in the Fågelsång area, Scania, southern Sweden. Deep water graptolitic mudstone and shale comprise the succession, and previously only one gastropod species was known. The new material spans the Sularp Formation through the Lindegård Mudstone (Nemagraptus gracilisDicellograptus complanatus biozones). Fourteen species are described: two tergomyan, five bellerophontoid gastropods, and seven anisostrophically coiled gastropods.Three species are new: Peelerophon hodites, Tetranota scanica and Lophospira sandbiana. Three taxa (Tritonophon subtrilobatus,Tetranota scanica and Holopea mobergi) are found high in the Lindegård Mudstone (Vormsi–Pirgu stages). Cyrtodiscus, Peelerophon and Tritonophon are recorded for the first time in Baltoscandia. Some taxa may have been transportedfrom shallower water settings, whereas species of Peelerophon, Joleaudella, Mestoronema and Sinuites may have been partof the local benthos. Except for Bucania erratica, no species are shared with the fauna of the coeval Dalby Limestone in Sweden. Deaechospira elliptica, common in the Dalby Limestone, is not recorded at Fågelsång, although two closely relatedspecies are found (Deaechospira rotunda and Deaechospira? sp.). The Fågelsång assemblage has more in common with the older to coeval fauna of the Elnes and Arnestad formations in the Oslo Region, Norway (e.g. sharing Joleaudella, Sinuites, Mestoronema and Pararaphistoma). The Sandbian fauna of Fågelsång includes peri-Gondwanan taxa, e.g. Cyrtodiscus,Peelerophon and Deaechospira. Nevertheless, cluster analysis reveals that the faunas of Baltica and Laurentia were most similar, whereas faunas from Perunica and Baltica remained distinct and separated during the Darriwilian–Sandbian. The few similarities may result from spread of a temperate fauna supplementing rather than replacing taxa in deep water assemblages.The main Fåagelsång assemblage coincides both with the Baltoscandian Middle Caradoc Faunal Turnover and the Gutenberg Carbon Isotope Excursion.

  • 5. Egenhoff, Sven
    et al.
    Cassle, Christopher
    Maletz, Jörg
    Ebbestad, Jan Ove
    Uppsala University, Music and Museums, Museum of Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Frisk, Åsa M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Tectonically-Induced Lowstand on an Ordovician Ramp – the Björkåsholmen Formation of Scandinavia2008In: 2008 Houston Annual Meeting (5–9 October 2008).: Geological Society of America Abstracts with Programs, Geological Society of America , 2008, p. 393-Conference paper (Other academic)
    Abstract [en]

    The Tremadoc Björkåsholmen Formation is an approximately one meter thick unit consisting of several carbonate beds with intercalated shales and some glauconite content in its upper part. It is underlain by the Cambrian-Ordovician Alum Shale Formation throughout Scandinavia, and in Norway and westernmost Sweden overlain by the Lower- to Middle Ordovician Tøyen Formation. The Björkåsholmen Formation is remarkably widespread in Scandinavia with relatively little variation in thickness or faunal composition. Internally, the unit consists of thin beds at the base with thicker ones in the center and again thinner beds towards the top. Thin beds are generally mud-rich while thicker ones display packstones. In the Norwegian sections the grain-rich facies have been mostly diagenetically overprinted, whereas eastern Swedish localities are characterized by much better facies preservation regardless of lithology. The overall mud-rich facies of the Björkåsholmen Formation reflects deposition on a low-inclined ramp environment. Coarse-grained sediments represent the proximal facies while increasing mud content shows deeper water middle to outer ramp deposition. Facies trends indicate that the Björkåsholmen Formation consists of at least five regressions and successive transgressions with a maximum lowstand represented by its coarse-grained central portion. As the Björkåsholmen Formation is sandwiched between two prominent outer shelf shales in the Norwegian and westernmost Swedish localities it also represents the most pronounced sea-level lowstand in the Early Ordovician of Scandinavia.This lowstand is within the upper part of the Aorograptus victoriae Biozone and the basal Kiaerograptus supremus Biozone. Deposition of the Björkåsholmen Formation therefore likely represents a fairly short time-span. However, this remarkably strong lowstand in Scandinavia is not paralleled by base-level falls in Bolivia, China or Newfoundland. It is therefore suggested that the Björkåsholmen Formation reflects a tectonic rather than a eustatic event which is restricted exclusively to Baltoscandia.

  • 6.
    Egenhoff, Sven
    et al.
    Colorado State Univ, Dept Geosci, Ft Collins, CO 80523 USA.
    Maletz, Jörg
    Free Univ Berlin, Inst Geowissensch, Berlin, Germany.
    Ahlberg, Per
    Lund Univ, Dept Geol, Lund, Sweden.
    Mast, Allison
    Colorado State Univ, Dept Geosci, Ft Collins, CO 80523 USA.
    Frisk, Åsa
    Uppsala University, Music and Museums, Museum of Evolution.
    Ebbestad, Jan Ove R.
    Uppsala University, Music and Museums, Museum of Evolution.
    Newby, Warren
    Colorado State Univ, Dept Geosci, Ft Collins, CO 80523 USA;Total Oil & Gas, Houston, TX 77010 USA.
    Sedimentology of the Lower Ordovician (upper Tremadocian) Bjørkasholmen Formation at Flagabro, southern Sweden2018In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 140, no 1, p. 55-65Article in journal (Refereed)
    Abstract [en]

    The Lower Ordovician Bjørkasholmen Formation at Flagabro, Scania, southern Sweden, consists of a 0.8m thick succession of carbonates with three siliciclastic mudstones, 5, 1 and 100mm thick, intercalated in the central part of the unit. Carbonate and siliciclastic mudstone beds show both normal and inverse grading. The carbonates are mud-rich and subdivided into a mudstone, a wackestone and a packstone facies. Grain types in the carbonates are mostly shells and shell fragments of brachiopods and trilobites. The carbonate rocks are strongly bioturbated seen as in roundish burrows filled with mud and a clear cement; additionally, bioturbation is reflected in the random orientation of shells. The siliciclastic mudstones are subdivided into two facies; one contains large amounts of shells and is in part grain-supported, the other is matrix-dominated and laminated to massive. The succession reflects sedimentation on a low-inclined shelf equivalent to a mid-ramp to basinal setting. Most mud- and wackestones (facies 3 and 4) represent fair-weather sedimentation, and the intercalated wacke- and packstones (facies 4 and 5) represent concentration of shell debris during high-energy storm. The siliciclastic mudstones in the central part of the succession reflect deposition in a basinal setting. The entire BjOrkasholmen Formation at Flagabro is equivalent to a lowstand of third (?) order without a well-developed internal cyclicity and is in that respect similar to the Bjørkasholmen Formation of oland, but different from the age-equivalent Norwegian sections.

  • 7.
    Frisk, Åsa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    The Bjorkåsholmen Formation (Tremadoc): a homogenous distribution of Trilobites throughout the Baltoscandian platform2005In: Lundadagarna i Historisk geologi och paleontologi IX, 2005Conference paper (Other scientific)
    Abstract [en]

    THE BJØRKÅSHOLMEN FORMATION (TREMADOC): A HOMOGENOUS DISTRIBUTION OF TRILOBITES THROUGHOUT THE BALTOSCANDIAN PLATFORM

    Åsa Frisk

    Uppsala University, Department of Earth Sciences, Palaeobiology, Norbyvägen 22, SE-752 36 Uppsala, Sweden.

    Extensive carbonate depositions initiate the Lower Ordovician succession of Baltoscandia forming the Tremadoc Bjørkåsholmen Formation, formerly the Ceratopyge Limestone, a distinctive unit corresponding to the trilobite zone of Apatokephalus serratus. In older studies a combined bio-litho stratigraphical concept of the unit has mostly been used, however a modern lithostratigraphical definition was given by Owen et al. (1990). The definition of the formation is based on the hypostratotype at Bjørkåsholmen in Slemmestad, Norway, and should be referred to instead of the historical synonym. The limestone succession has a broad regional distribution and its associated sediments were deposited across the Baltoscandian platform in a shallow water epicontinental sea. Similar depositional conditions are not known today. The unit is remarkable in its near homogenous facies, lithologic and faunal composition throughout the platform. The most recent revision of trilobites from the Ceratopyge fauna recognized 36 species assigned to 28 genera (Ebbestad 1999).

    In the present study sequences at Ottenby and Degerhamn on southern Öland, Sweden, were logged and compared for trilobite biostratigraphy. In both investigated localities the resulting trilobite abundance distributions are very consistent. The trilobite fauna from the Bjørkåsholmen Formation in the Oslo Region, Norway, and Öland are composed of the same typical Ceratopyge assemblage. Trilobite abundance data from both areas are nearly identical and demonstrate an upward declination of trilobite specimens. Comparison across the Baltoscandian platform between the westernmost occurrences in the Oslo Region and the easternmost outcrops on Öland therefore suggests widespread stable conditions of the Ceratopyge fauna during the sedimentation of the Bjørkåsholmen Formation.

    Ebbestad, J.O.R. 1999: Trilobites of the Tremadoc Bjørkåsholmen Formation in the Oslo Region, Norway. Fossils and Strata 47. 118 pp.

    Owen, A.W., Bruton, D.L., Bockelie, J.F. Bockelie, T.G. 1990: The Ordovician successions of the Oslo Region, Norway. Norges geologiske undersøkelse Special Publication 4. 54 pp.

  • 8.
    Frisk, Åsa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    The Bjørkåsholmen Formation (Tremadoc): a homogenous distribution of trilobites throughout the Baltoscandian platform2004In: 48th Palaeontological Association Annual Meeting: Lille 2004, 2004, p. 199-Conference paper (Other scientific)
    Abstract [en]

    The Bjørkåsholmen Formation (Tremadoc): a homogenous distribution of trilobites throughout the Baltoscandian platform

    Åsa Frisk

    Department of Earth Sciences, Palaeobiology, Uppsala University, Norbyvägen 22, SE-752 36 Uppsala, Sweden <asa.frisk@geo.uu.se>

    The Lower Ordovician succession of Baltoscandia is initiated by extensive carbonate deposition forming the Tremadoc Bjørkåsholmen Formation, formerly the Ceratopyge Limestone, a distinctive unit corresponding to the trilobite zone of Apatokephalus serratus. The limestone succession has a broad regional distribution and its associated sediments were deposited across the Baltoscandian platform in a shallow water epicontinental sea. Similar depositional conditions are not known today. The unit is remarkable in its near homogenous facies, lithologic and faunal composition throughout the platform. This is clearly demonstrated in the present study, where sequences at Ottenby and Degerhamn on southern Öland, Sweden, were logged and compared for trilobite biostratigraphy. In both investigated localities the resulting trilobite abundance distributions are very consistent. The trilobite fauna from the Bjørkåsholmen Formation in the Oslo Region, Norway, and Öland are composed of the same typical Ceratopyge assemblage. Trilobite abundance data from both areas are nearly identical and demonstrate an upward declination of trilobite specimens. Comparison across the Baltoscandian platform between the westernmost occurrences in the Oslo Region and the easternmost outcrops on Öland therefore suggests widespread stable conditions of the Ceratopyge fauna during the sedimentation of the Bjørkåsholmen Formation.

  • 9.
    Frisk, Åsa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Trilobite biostratigraphy of the Tremadoc Bjørkåsholmen Formation on Öland, Sweden2004In: WOGOGOB-2004 Conference materials, 2004, p. 141-Conference paper (Other scientific)
    Abstract [en]

    Trilobite biostratigraphy of the Tremadoc Bjørkåsholmen Formation on Öland, Sweden

    The Lower Ordovician of Baltoscandia is characterized by the initiation of extensive carbonate deposits of the Ceratopyge Limestone. The limestone succession has a broad regional distribution and its associated sediments were deposited in a shallow water epicontinental sea across the Baltic platform during the late Tremadoc (Jaanusson 1976, 1982; Dronov & Holmer 1999). Those particular depositional factors have no present day equivalents. The unit is definitely remarkable in its apparent homogenous facies, lithological and faunal composition. The significance of the Ceratopyge Limestone succession was early referred by numerous authors and recognized sedimentologically and stratigraphically. Tjernvik (1956) reinvestigated the Lower Ordovician beds in Sweden in detail and completed an account of the rich Ceratopyge fauna.

    In older studies a combined bio-litho stratigraphical concept of the unit has mostly been used, however a modern lithostratigraphical definition was given by Owen et al. (1990). The definition of the formation is based on the hypostratotype at Bjørkåsholmen in Slemmestad, Norway, and should be referred to instead of the historical synonym. The transition from the dark underlying Alum Shale Formation to the grey limestone beds marks the base of the Bjørkåsholmen Formation (BHF), this is evident in the change in not only lithology but also the typical associated fauna e.g. the Ceratopyge fauna (Tjernvik 1956; Ebbestad 1999). In Sweden the BHF is followed by the Hunneberg-Billingen Latorp Limestone and Volkhov Lanna Limestone. Shales of the Tøyen Formation follow the partially glauconitic limestone in Norway (Owen et al. 1990). The most recent revision of the trilobite fauna recognized 36 species assigned to 28 genera (Ebbestad 1999).

    The present study investigates trilobite distribution of the BHF in southern Öland, the easternmost outcrop of the formation. The underlying crystalline bedrock on Öland dips weakly to the east resulting in the exposition of the oldest overlying sedimentary rocks in the west and the youngest beds in the east (Jaanusson & Mutvei 1982). The upper Cambrian Alum Shale Formation is continued in the Lower Ordovician successions and is subsequently overlain by the upper Tremadoc limestone deposits represented by the BHF. Outcrops of this unit are fairly rare, confined to a few localities in the southern and south-central parts of the island.

    The material presented in this study was collected at the coastal section at Ottenby and at the Cementa quarry in Degerhamn. Sequences at Ottenby and Degerhamn were logged and material collected for a biostratigraphical study. To obtain trilobite abundances the sample frequency method (Jaanusson 1979; Nielsen 1995; Ebbestad 1999) was applied. The lower boundary of the BHF in Öland is marked by the occurrence of glauconiferous limestone nodules, represented in both localities. The main limestone beds in Öland, e.g. constituting continuous beds having the main trilobite abundance, are grey and micritic, and with some intercalations of glauconitic shale. In addition scattered grains of glauconite and small accumulations of pyrite are evident in the main limestone. The uppermost bed in the two successions, devoid in trilobites, marks the upper boundary of the formation, it is also exceptionally glauconitic suggesting slow deposition and starvation of sedimentation. The BHF at both Degerhamn and the Ottenby section has an approximately thickness of 0.6 meter and several discontinuity surfaces are evident.

    The trilobite abundance logs give a proposal for the distribution of the trilobite fauna during the upper Tremadoc in Öland. The material collected from the section in Degerhamn and Ottenby belongs to the Ceratopyge fauna and biostratigraphically the unit is connected to the Apatokephalus serratus Zone. The trilobite abundance distribution from each of the localities is very consistent. Additionally, the fossil assemblages in Öland and the Oslo Region (Ebbestad 1999) are built up by the same typical Ceratopyge fauna, indicating a correlation. Faunal signals show several similarities in the trilobite abundance data and both areas have an upwards declination of trilobite quantities in the sequences. Faunal distribution of trilobites of the Ceratopyge fauna is thus very coherent throughout the platform. This suggests widespread stable conditions of the fauna throughout the Baltic Platform during sedimentation of the BHF. The Central Baltoscandian Confacies Belt (Jaanusson 1976), to which Öland belongs, and the Oslo Region belonging to the Oslo Confacies Belt, demonstrate no facies differentiation of the platform until post-Tremadoc (Jaanusson & Mutvei 1982).

    The basal limestone nodules at the two investigated sections are devoid of trilobite remains. Periods of oxygenated lime mud sedimentation, reflected by the basal limestone nodules incorporated in the shale, may indicate times of fluctuations in the sea level. The main limestone units have little or no intercalations of shale, thus representing episodes of more stable sedimentary facies. The unstable settings may suggest non-favourable environments for the establishment of nileid communities (Fortey 1975), here represented by the Ceratopyge fauna, described by the absence of trilobites in the lowermost limestone nodules. Fluctuations of the sea level was probably confined to local settings and are suggested by extended periods with large inputs of oxygen during lime mud sedimentation. Constrained settings are most likely a result of diverse bottom topography and differences in current and wave distribution throughout the area (Ebbestad 1999). The faunal logs clearly demonstrate this idea. Ebbestad (1999) stated similar conditions for the depositions of the basal limestone beds in the BHF of the Oslo Region. The Ceratopyge fauna display coherent distribution in Öland and certainly across the platform, moreover, the distribution does not correlate with specific beds, presumably demonstrating dissimilar sedimentological developments of the two localities, suggesting that the deposition was diachronous.

    The upper Tremadoc and early Arenig represents a time of large global sea-level changes by the lowering of the seas (Fortey 1984), this event the Ceratopyge Regressive Event (CRE) (Erdtmann & Paalits 1995) could have resulted in the depletion of sediments. In Baltica this is clearly shown by the end of the Apatokephalus serratus zone, the top of the Bjørkåsholmen Formation, and in addition the disappearance of its associated Ceratopyge fauna.

    References:

    Dronov, A. & Holmer, L. 1999: Depositional sequences in the Ordovician of Baltoscandia. Acta

    Universitatis Carolinae - Geologica 43, 133-136.

    Ebbestad, J.O.R. 1999: Trilobites of the Tremadoc Bjørkåsholmen Formation in the Oslo Region,

    Norway. Fossils and Strata 47. 118 pp.

    Erdtmann, B.D. & Paalits, I. 1995: The Early Ordovician ’Ceratopyge Regressive Event’ (CRE): its

    correlation and biotic dynamics across the East European Platform. Lithuanian Geological Society,

    Geologija, 1994, 17, 36-57.

    Fortey, R.A. 1984: Global earlier Ordovician transgressions and regressions and their biological

    implications. In: Bruton, D.L. (ed.). Aspects of the Ordovician System. Palaeontological

    Contributions from the University of Oslo, No. 295, Universitetsförlaget, 37-50.

    Jaanusson, V. 1976: Faunal dynamics in the Middle Ordovician (Viruan) of Baltoscandia. In: Basett

    M.G. (ed): The Ordovician System. University of Wales Press, Cardiff, 301-326.

    Jaanusson, V. 1979: Ecology and faunal dynamics. In: Jaanusson, V., Laufeld, S. & Skoglund, R.

    (eds:): Lower Wenlock faunal and floral dynamics – Vattenfallet Section, Gotland. Sveriges

    Geologiska Undersäkning C 762, 253-294.

    Jaanusson, V. & Mutvei, 1982: Jaanusson, V. & Mutvei, H. 1982: Ordovician of Öland. Guide to

    exkursion 3. IV International Symposium on the Ordovician System, Oslo 1982, 23 pp.

    Nielsen, A.T. 1995: Trilobite systematics, Biostratigraphy and palaeoecology of the Lower Ordovician

    Komstad and Huk Formations, southern Scandinavia. Fossils and Strata 38. 374 pp.

    Owen, A.W., Bruton, D.L., Bockelie, J.F. Bockelie, T.G. 1990: The Ordovician successions of the

    Oslo Region, Norway. Norges geologiske undersøkelse Special Publication 4. 54 pp.

    Tjernvik. T.E. 1956: On the Early Ordovician of Sweden. Bulletin of the Geological Institutions of

    Uppsala 35, 108-284.

  • 10.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Palaeobiologi.
    Ebbestad, Jan Ove
    Uppsala University, Museums etc., Museum of Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Diversity and distribution of paragastropods, tergomyans and gastropods in the Upper Ordovician Dalby Limestone, Sweden.2007In: Palaeontological Association 51st Annual Meeting: Uppsala University, Sweden, 2007, p. 1-Conference paper (Other (popular scientific, debate etc.))
  • 11.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Holmer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Linguliform and Craniiform Brachiopods from the Ordovician Tvären Crater, Sweden2005In: The 5th International Brachiopod Conference, Copenhagen, Denmark, 2005Conference paper (Other scientific)
    Abstract [en]

    Linguliform and Craniiform Brachiopods from the Ordovician Tvären Crater, Sweden

    Åsa M. Frisk1 and Lars E. Holmer1

    1Department of Earth Sciences, Palaeobiology, Uppsala University, Norbyvägen 22, SE-752 36 Uppsala, Sweden

    During the Ordovician several bolides hit the Baltoscandian Epicontinental Sea. One of the impacts occurred at a water depth of 300 m and resulted in the 2 km wide Tvären crater, now situated in the Stockholm Archipelago, Sweden. The pre-impact sedimentary sequence at Tvären consisted of Ordovician carbonates resting on non-lithified sands of Early to earliest Middle Cambrian age. Following the impact event, deposition of carbonates continued (Dalby Limestone). The crater acted like a sheltering rim for the deposition of sediments, also displaying pure new settings for the fauna still living in the surrounding sea.

    The studied material from Tvären consists of glacial erratics from the area immediately southeast of the bay of Tvären on the coast of Södermanland. The limestone boulders are all fairly fossiliferous and have yielded numerous ostracods and brachiopods, the brachiopods being the next most common group; however the brachiopod fauna has never been previously studied in detail. The linguliform brachiopod fauna recorded from the erratic boulders include a large new lingulid genus and species, as well as new species of Schizotreta and Paterula. Eoconulus robustus Holmer is the only linguliform species previously recorded from the Dalby Limestone in Sweden.

  • 12.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Lindström, Maurits
    Holmer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    A marine impact crater as an Ordovician ecosystem; the Tvären crater2005In: SEPM Research Conference; The sedimentary Record of Meteorite Impacts, 2005Conference paper (Other scientific)
    Abstract [en]

    A marine impact crater as an Ordovician ecosystem; the Tvären crater

    Frisk, Å.1, Lindström, M.2 & Holmer, L.E1

    1Department of Earth Sciences, Palaeobiology, Uppsala University, Norbyvägen 22, SE-752 36 Uppsala, Sweden, asa.frisk@geo.uu.se, lars.holmer@pal.uu.se

    2Department of Geology and Geochemistry, Stockholm University, Sweden, maurits.lindström@geo.su.se

    The Tvären crater was formed as a result of an impact in the Ordovician Baltoscandian epicontinental sea, now situated in the Stockholm Archipelago, Sweden. The bolide impact resulted in an approximately 2 km wide crater and the pre-impact sedimentary sequence consists of Ordovician carbonates resting on non-lithified sands of Early to earliest Middle Cambrian age. After the impact event and the settling of the impact ejecta and resurge material, deposition of carbonates continued (Dalby Limestone). The lithology and thickness of the post-impact Dalby Limestone vary depending on the depositional environment relative to the cratered seascape. The crater itself acted like a sheltering rim for the deposition of sediments, also causing a fairly rapid sedimentation rate compared to the normal sedimentation of the Dalby limestone. The area consequently displayed pure new settings for the marine fauna still living in the surrounding sea, though not affected by the impact, and thus creating a new ecosystem. This particular condition makes it possible to get a good precision of the sedimentation and faunal succession occurring in the crater. Drillings in the Tvären crater were conducted in 1991 resulting in an almost complete drill core through the sedimentary succession in the crater. The base of the core consists of crystalline breccia followed by resurge deposits and then the sedimentation of the Dalby Limestone. The post-impact fossil fauna mostly consists of chitinozoans, graptolites, trilobites, bryozoans, ostracodes, echinoderms, cephalopods and brachiopods. Certain groups are restricted to deeper or lower water levels, varying during the sedimentation, while some occur throughout the succession. A detailed biostratigraphy through the post-impact succession of the drill core is being conducted to understand how the abundance of species changed in relation to the varied environments and how the pre-impact faunal groups recovered gradually as life returned onto a sterile seafloor.

  • 13.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Lindström, Maurits
    Holmer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Faunal recovery in the Ordovician Lockne and Tvären craters2005In: Lundadagarna i Historisk Geologi och Paleontologi IX, 2005Conference paper (Other scientific)
    Abstract [en]

    FAUNAL RECOVERY IN THE ORDOVICIAN LOCKNE AND TVÄREN CRATER

    Åsa Frisk1, Maurits Lindström2 & Lars Holmer1

    1Uppsala University, Department of Earth Sciences, Palaeobiology, Norbyvägen 22, SE-752 36 Uppsala, Sweden.

    2Stockholm University, Department of Geology and Geochemistry, SE-106 91 Stockholm, Sweden

    Limited amount of work has been carried out looking at the aftermath of marine impacts; in particular the patterns of faunal recovery in and around marine craters have never been studied in detail. In Baltoscandia several marine impacts occurred during the Ordovician, and this project focuses on the Lockne and Tvären craters. The Lockne crater in Jämtland, Sweden, is well exposed on land while the Tvären crater, located under water in the Stockholm archipelago, Sweden, is available as drill cores and erratic boulders. The impacted sedimentary sequence at Tvären consisted of Ordovician carbonates resting on non-lithified sands of Early to earliest Middle Cambrian age whereas at Lockne the same kind of limestone rests on Middle to Upper Cambrian bituminous mud. After the impact events and the settling of the impact ejectas and resurge materials, deposition of carbonates continued (Dalby Limestone).

    After impact the substrate became devoid of life. Large areas were affected by the local extinction of the fauna and thus provided virgin ground for the settling of marine fauna still living in the surrounding sea, though not affected by the impact. A dramatic alteration of the seafloor topography, caused by the impact, offered new habitats characterized by the crater morphology and sheltering rims. The immigrating biota, mostly consisting of chitinozoans, graptolites, trilobites, bryozoans, ostracodes, echinoderms, cephalopods and brachiopods, developed new ecosystems. Certain groups are restricted to deeper or lower water levels, varying during the sedimentation in the crater, while some occur throughout the succession. A detailed biostratigraphic study of the post-impact succession in the craters is being carried out in order to understand how the abundance of species changed in relation to the varied environments and how the pre-impact faunal groups recovered gradually as life returned onto a sterile seafloor.

  • 14.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Lindström, Maurits
    Paleobiologi.
    Holmer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Paleobiologi.
    Palaeoecology of a marine impact crater in the Ordovician sea2005In: Palaeontological Association 49th Annual Meeting: University of Oxford, 2005Conference paper (Other scientific)
    Abstract [en]

    Palaeoecology of a marine impact crater in the Ordovician sea

    Åsa Frisk1, Maurits Lindström2 and Lars Holmer1

    1Department of Earth Sciences, Palaeobiology, Uppsala University, Sweden

    2Department of Geology and Geochemistry, Stockholm University, Sweden

    The aftermath of marine impacts, in particular the patterns of faunal recovery in and around marine craters, are poorly understood. In the Ordovician Baltoscandian epicontinental sea a bolide impact resulted in the Tvären crater. At present it is located in the Stockholm archipelago, Sweden, where drillings in 1991 resulted in two drill cores.

  • 15.
    Frisk, Åsa M
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Late Ordovician Faunal Distribution and Ecospace Partitioning in Marine Impact Craters: The Aftermath of the Lockne and Tvären Events2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the Middle to Late Ordovician a boost of marine biodiversity occurred which is regarded as the most rapid diversity in Earth’s history, and termed the Great Ordovician Biodiversification Event. This time is also unique in that at least four marine meteorite craters with a good record of post-impact sediments are preserved in Baltoscandia. Catastrophic impacts can serve as constructive events and produce wide-ranging environments providing new ecological niches for a diverse biota to occupy. Additionally, they generate distinctive patterns of biological destruction and recovery. This, and the study of distribution and ecospace utilisation of Late Ordovician faunas, has been analysed in two almost contemporary (around 455 million years ago) meteorite craters (Lockne and Tvären, Sweden). Within the confined space of the impact craters environments varied from shallow and reef-like to over 200 m in depth and from well oxygenated to hypoxic. These types of environments favored colonization of different individual groups. In Tvären rhynchonelliformean brachiopod assemblages from the shallow crater rim include a range of morphotypes, not established elsewhere in the crater. Within the crater depression rhynchonelliformean brachiopods were not established until the upper third of the remaining crater fill. Colonization of post-impact faunas varies dependent on topography, depth and susbstrate within the impact craters. This is recognised for scolecodonts in Tvären and for gastropod-like mollusks, linguliform and craniiform brachiopods in both of the craters, as they inhabit a wide range of ecospace. A succession of different taxa is observed from the deepest part of each crater and upwards towards inferably more shallow, higher energy, water settings. The development of new community types and narrowly-defined niches in the craters helped further drive both α and β biodiversity during a critical phase of the Great Ordovician Biodiversification Event.

    List of papers
    1. Facies distribution of post- impact sediments in the Ordovician Lockne and Tvären impact craters: Indications for unique impact-generated environments
    Open this publication in new window or tab >>Facies distribution of post- impact sediments in the Ordovician Lockne and Tvären impact craters: Indications for unique impact-generated environments
    2007 (English)In: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 42, no 11, p. 1971-1984Article in journal (Refereed) Published
    Abstract [en]

    The Lockne and Tvaren craters formed in the Late Ordovician Baltoscandian epicontinental sea. Both craters demonstrate similarities concerning near-synchronous age, target seabed, and succeeding resurge deposits; however, the water depths at the impact sites and the sizes of the craters were not alike. The post-impact sedimentary succession of carbonates, i.e., the Dalby Limestone, deposited on top of the resurge sediments in the two craters, is nevertheless similar. At least three main facies of the Dalby Limestone were established in the Lockne crater, depending on sea-floor topography, location with respect to the crater, and local water currents. The dominating nodular argillaceous facies, showing low values of inorganic carbon (IC), was distributed foremost in the deeper and quiet areas of the crater floor and depressions. At the crater rim, consisting of crushed crystalline basement ejecta, a rim facies with a reef-like fauna was established, most certainly due to topographical highs and substrate-derived nutrients. Between these facies are occurrences of a relatively thick-bedded calcilutite rich in cephalopods (cephalopod facies). In Tvaren, the lower part of the succession consists of an analogous argillaceous facies, also showing similar low IC values as in Lockne, followed by calcareous mudstones with an increase of IC. Occasionally biocalcarenites with a distinctive fauna occur in the Tvaren succession, probably originating as detritus from a facies developed on the rim. They are evident as peaks in IC and lows in organic carbon (Corg). The fauna in these biocalcarenites corresponds very well with those of erratic boulders derived from Tvaren; moreover, they correspond to the rim facies of Lockne except for the inclusion of photosynthesizing algae, indicating shallower water at Tvaren than Lockne. Consequently, we suggest equivalent distribution patterns for the carbonates of the Dalby Limestone in Lockne and Tvaren.

    National Category
    Earth and Related Environmental Sciences
    Identifiers
    urn:nbn:se:uu:diva-12757 (URN)10.1111/j.1945-5100.2007.tb00554.x (DOI)000253937700011 ()
    Available from: 2008-05-19 Created: 2008-05-19 Last updated: 2017-12-11Bibliographically approved
    2. Paragastropoda, Tergomya and Gastropoda (Mollusca) from the Upper Ordovician Dalby Limestone, Sweden
    Open this publication in new window or tab >>Paragastropoda, Tergomya and Gastropoda (Mollusca) from the Upper Ordovician Dalby Limestone, Sweden
    2007 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 129, no 2, p. 83-99Article in journal (Refereed) Published
    Abstract [en]

    A fauna of 12 species of paragastropods, tergomyans and gastropods is described from the Upper Ordovician (Kukruse Stage to Idavare substage) Dalby Limestone of Tvären, Lockne, and Fjäcka (Sweden), presenting a higher diversity than previously recognized. The presence of Mimospira, Laeogyra, Sarkanella epelys n. sp. indicates a strong faunal connection with Bohemia, Czech Republic. Sarkanella is reported from outside Bohemia for the first time. Bucania erratica n. sp. represents one of the earliest records of the genus in Baltoscandia. A single case of shell repair from failed predation is recorded in this species. Synonyms for Eccyliopterus princeps Remelé and E. regularis Remelé are proposed. The significance of Laeogyra, Eccyliopterus, and Deaechospira for regional correlation within the Upper Ordovician of Baltoscandia is confirmed.

    Keywords
    Biogeography, Dalby Limestone, Fjäcka, Gastropoda, Lockne, Paragastropoda, Sweden, Tergomya, Tvären, Upper Ordovician
    National Category
    Earth and Related Environmental Sciences
    Identifiers
    urn:nbn:se:uu:diva-11257 (URN)10.1080/11035890701292083 (DOI)000248408400004 ()
    Available from: 2007-12-29 Created: 2007-12-29 Last updated: 2017-12-11Bibliographically approved
    3. Marine astrobleme palaeoecology in the early Late Ordovician of Sweden  
    Open this publication in new window or tab >>Marine astrobleme palaeoecology in the early Late Ordovician of Sweden  
    (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
    Identifiers
    urn:nbn:se:uu:diva-109569 (URN)
    Available from: 2009-10-20 Created: 2009-10-19 Last updated: 2010-01-14
    4. Late Ordovician brachiopod distribution and ecospace partitioning in the Tvären crater system, Sweden
    Open this publication in new window or tab >>Late Ordovician brachiopod distribution and ecospace partitioning in the Tvären crater system, Sweden
    2013 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 369, p. 114-124Article in journal (Refereed) Published
    Abstract [en]

    Patterns of distribution and ecospace utilization of Late Ordovician brachiopods in a recently formed, contemporary meteorite crater are described and analyzed. Rhynchonelliformean brachiopod communities, dominated by a wide range of orthides and strophomenides, colonized the newly formed crater. At the crater rim communities were established early on, although the crater depression was not inhabited until deposition of the upper third of the remaining crater fill. The crater formed a protected but restricted microenvironment where sediments four times the thickness of the nearby basinal succession accumulated. Within this narrow space environments varied from shallow-water to deeper-waters, about 200 m in depth, and from well oxygenated to hypoxic. Such varied environments generated a rough ecological landscape, facilitating niche partitioning across a relatively small geographic area. Analysis of the guild structure of the fauna permits explanation of a local biodiversity hotspot in otherwise low-diversity strata elsewhere in the Scandinavian region. The Tvären impact event had an important palaeobiologic effect upon the fossil record as it served as a local pump and reservoir for biodiversity. Moreover the development of new community types and narrowly-defined niches helped further drive both α and β biodiversity during a critical phase of the Great Ordovician Biodiversification Event.

    National Category
    Geology
    Research subject
    Historical Geology and Paleontology
    Identifiers
    urn:nbn:se:uu:diva-109567 (URN)10.1016/j.palaeo.2012.10.008 (DOI)000315127200010 ()
    Available from: 2009-10-20 Created: 2009-10-19 Last updated: 2017-12-12Bibliographically approved
    5. Palaeoenvironmental aspects of Late Ordovician (Sandbian) Sericoidea shell concentrations in an impact crater, Tvären, Sweden.
    Open this publication in new window or tab >>Palaeoenvironmental aspects of Late Ordovician (Sandbian) Sericoidea shell concentrations in an impact crater, Tvären, Sweden.
    (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
    Identifiers
    urn:nbn:se:uu:diva-109602 (URN)
    Available from: 2009-10-20 Created: 2009-10-20 Last updated: 2010-01-14
    6. Diversity and distribution of post-impact Linguliform and Craniiform brachiopod colonizers in Upper Ordovician marine impact craters
    Open this publication in new window or tab >>Diversity and distribution of post-impact Linguliform and Craniiform brachiopod colonizers in Upper Ordovician marine impact craters
    (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
    National Category
    Geology
    Research subject
    Historical Geology and Paleontology
    Identifiers
    urn:nbn:se:uu:diva-109568 (URN)
    Available from: 2009-10-20 Created: 2009-10-19 Last updated: 2012-12-11Bibliographically approved
    7. Gastropods from the Upper Ordovician (Viru-Harju) of the Fågelsång area, Scania, southern Sweden
    Open this publication in new window or tab >>Gastropods from the Upper Ordovician (Viru-Harju) of the Fågelsång area, Scania, southern Sweden
    (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
    Identifiers
    urn:nbn:se:uu:diva-109601 (URN)
    Available from: 2009-10-20 Created: 2009-10-20 Last updated: 2010-03-29
  • 16.
    Frisk, Åsa M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology. Paleobiologi.
    Ebbestad, Jan Ove R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Paleobiologi.
    Biostratigraphy of an Early Ordovician (Tremadoc) epicontinental carbonate facies: the Baltoscandian Bjørkåsholmen Formation2006In: Geological Society of America Abstracts with Programs, 2006, p. 551-551Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The Lower Ordovician in Baltoscandia was initiated by extensive carbonate deposition forming the Tremadoc Bjørkåsholmen Formation (formerly the Ceratopyge Limestone), a distinctive unit corresponding to the Apatokephalus serratus trilobite Zone. The unit is remarkable in its near homogenous facies, lithologic and faunal composition throughout the Baltoscandian platform, representing a shallow water epicontinental environment. Similar facies are recognized in the autochthonic Caledonides believed to have been deposited 400 km to the west of the present Norwegian shoreline, while the easternmost outcrops are found on the island Öland off the east coast of Sweden. This gives an east-west extension of nearly 2000 kilometres, while the north-south extension is less well known owing to lack of exposures. However, glauconitic sandstones replace the carbonates both in the Siljan District of Dalarna, Sweden, and in the easternmost baltoscandian platform in Estonia and the St. Petersburg area of Russia. Trilobites are the dominant fossil group, with 36 species belonging to 26 genera. For the ongoing study of trilobite biostratigraphy of the unit, the trilobite abundance distribution has been investigated for two localities on southern Öland, Sweden. In both investigated sections the resulting abundance distributions are consistent, with diversity declining upward. The abundancy distribution compares in detail with several sections studied earlier from the Oslo Region of Norway. A section in Västergötland, halfway between the Oslo Region and Öland, is currently also under study. However, preliminary comparison across the Baltoscandian platform between the Oslo Region and Öland, suggests an extensive stable environment and fauna during deposition of the Bjørkåsholmen Formation.

  • 17.
    Frisk, Åsa M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Ebbestad, Jan Ove R.
    Uppsala University, Music and Museums, Museum of Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Paragastropoda, Tergomya and Gastropoda (Mollusca) from the Upper Ordovician Dalby Limestone, Sweden2007In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 129, no 2, p. 83-99Article in journal (Refereed)
    Abstract [en]

    A fauna of 12 species of paragastropods, tergomyans and gastropods is described from the Upper Ordovician (Kukruse Stage to Idavare substage) Dalby Limestone of Tvären, Lockne, and Fjäcka (Sweden), presenting a higher diversity than previously recognized. The presence of Mimospira, Laeogyra, Sarkanella epelys n. sp. indicates a strong faunal connection with Bohemia, Czech Republic. Sarkanella is reported from outside Bohemia for the first time. Bucania erratica n. sp. represents one of the earliest records of the genus in Baltoscandia. A single case of shell repair from failed predation is recorded in this species. Synonyms for Eccyliopterus princeps Remelé and E. regularis Remelé are proposed. The significance of Laeogyra, Eccyliopterus, and Deaechospira for regional correlation within the Upper Ordovician of Baltoscandia is confirmed.

  • 18.
    Frisk, Åsa M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Ormö, Jens
    Facies distribution of post- impact sediments in the Ordovician Lockne and Tvären impact craters: Indications for unique impact-generated environments2007In: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 42, no 11, p. 1971-1984Article in journal (Refereed)
    Abstract [en]

    The Lockne and Tvaren craters formed in the Late Ordovician Baltoscandian epicontinental sea. Both craters demonstrate similarities concerning near-synchronous age, target seabed, and succeeding resurge deposits; however, the water depths at the impact sites and the sizes of the craters were not alike. The post-impact sedimentary succession of carbonates, i.e., the Dalby Limestone, deposited on top of the resurge sediments in the two craters, is nevertheless similar. At least three main facies of the Dalby Limestone were established in the Lockne crater, depending on sea-floor topography, location with respect to the crater, and local water currents. The dominating nodular argillaceous facies, showing low values of inorganic carbon (IC), was distributed foremost in the deeper and quiet areas of the crater floor and depressions. At the crater rim, consisting of crushed crystalline basement ejecta, a rim facies with a reef-like fauna was established, most certainly due to topographical highs and substrate-derived nutrients. Between these facies are occurrences of a relatively thick-bedded calcilutite rich in cephalopods (cephalopod facies). In Tvaren, the lower part of the succession consists of an analogous argillaceous facies, also showing similar low IC values as in Lockne, followed by calcareous mudstones with an increase of IC. Occasionally biocalcarenites with a distinctive fauna occur in the Tvaren succession, probably originating as detritus from a facies developed on the rim. They are evident as peaks in IC and lows in organic carbon (Corg). The fauna in these biocalcarenites corresponds very well with those of erratic boulders derived from Tvaren; moreover, they correspond to the rim facies of Lockne except for the inclusion of photosynthesizing algae, indicating shallower water at Tvaren than Lockne. Consequently, we suggest equivalent distribution patterns for the carbonates of the Dalby Limestone in Lockne and Tvaren.

  • 19.
    Frisk, Åsa
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Palaeobiologi.
    Ormö, Jens
    Facies distribution of post- impact sediments in the Ordovician Lockne and Tvären impact craters: Indications for unique impact-generated environments.2008In: 28th Nordic Geological Wintermeeting - Abstract volume: Aalborg Denmark, 2008, p. 1-Conference paper (Other (popular scientific, debate etc.))
  • 20.
    Hautmann, Michael
    et al.
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Bagherpour, Borhan
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Brosse, Morgane
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Frisk, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Hofmann, Richard
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Baud, Aymon
    Baud Geol Consultant, CH-1018 Lausanne, Switzerland..
    Nuetzel, Alexander
    GeoBioctr LMU, Dept Earth & Environm Sci Paleontol & Geobiol, SNSB Bayer Staatssammlung Palaontol & Geol, D-80333 Munich, Germany..
    Goudemand, Nicolas
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Bucher, Hugo
    Univ Zurich, Palaontol Inst & Museum, CH-8006 Zurich, Switzerland..
    Competition in slow motion: the unusual case of benthic marine communities in the wake of the end-Permian mass extinction2015In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 58, no 5, p. 871-901Article in journal (Refereed)
    Abstract [en]

    Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10-100ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the long-term effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.

  • 21. Wickström, Linda
    et al.
    Frisk, Åsa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Palaeobiologi.
    Lindström, Maurits
    Stratigraphic successions: WOGOGOB 2007. 9th meeting of the Working Group on Ordovician Geology of Baltoscandia. Field guide and Abstracts2007Other (Other (popular scientific, debate etc.))
  • 22. Wickström, Linda M.
    et al.
    Frisk, Åsa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology. Palaeobiologi.
    Dahlqvist, Peter
    Locality descriptions: the Östersund area. WOGOGOB 2007. 9th meeting of the Working Group on Ordovician Geology of Baltoscandia. Field guide and Abstracts2007Other (Other (popular scientific, debate etc.))
1 - 22 of 22
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