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Ebbestad, Jan Ove R.ORCID iD iconorcid.org/0000-0001-8769-3572
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Publications (10 of 181) Show all publications
Agic, H., Jensen, S., Meinhold, G., Hogstrom, A. E. S., Ebbestad, J. O., Hoyberget, M., . . . Taylor, W. L. (2024). Life through an Ediacaran glaciation: Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway. Palaeogeography, Palaeoclimatology, Palaeoecology, 635, Article ID 111956.
Open this publication in new window or tab >>Life through an Ediacaran glaciation: Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway
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2024 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 635, article id 111956Article in journal (Refereed) Published
Abstract [en]

New organic-walled microfossil (OWM) assemblages are reported from upper Neoproterozoic glacial and interglacial siliciclastic deposits in Finnmark, northern Norway. A nearly continuous sedimentary succession of the Vestertana Group contains two glaciogenic units, the Smalfjorden and Mortensnes formations, interpreted as end-Cryogenian Marinoan and Ediacaran glaciations, respectively. We investigated the OWM record in the Nyborg, Mortensnes, and St ' ahpogieddi formations to assess the impact of a glacial interval on the diversity of microscopic eukaryotes. A modified acid-extraction technique was applied to recover OWM from the diamictite matrix. The upper Nyborg Formation contains morphologically complex Doushantuo-Pertatataka acritarchs (DPA), restricting the age of the Nyborg Formation to early-mid Ediacaran. DPA occur below the dolostones that record a negative carbon isotope excursion correlated with the Shuram anomaly and below a glacial diamictite. A decline in species richness and compositional change is observed in the Mortensnes glacial assemblage. DPA are replaced by bacterial filaments and cell aggregates. The overlying Indreelva Member, St ' ahpogieddi Formation contains Ediacara-type biota and palaeopascichnids, but only a depauperate OWM assemblage of leiosphaerids and flask-shaped microfossils characteristic of the late Ediacaran.The succession of assemblages in the Vestertana Group demonstrates a turnover from large eukaryotic OWM to a microbial community in the glacial interval, to a low diversity post-glacial assemblage during the rise of macroscopic life. We compared the Vestertana record to global DPA occurrences. Although one DPA assemblage zone postdates the Shuram excursion, no DPA occur above Ediacaran glacial diamictites in successions where those deposits are present. Considering this, and the community changes in the Vestertana succession, we suggest that DPA were affected by the onset of an Ediacaran glaciation. Lastly, we combined the biostratigraphic markers in the Vestertana Group to constrain the age of the Mortensnes diamictite.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Organic-walled microfossils, Neoproterozoic, Ediacaran, Diamictite, Biostratigraphy, Palynological acid maceration
National Category
Geology Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-523232 (URN)10.1016/j.palaeo.2023.111956 (DOI)001140581900001 ()
Funder
Swedish Research Council, VR2016-06810
Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-02-19Bibliographically approved
Cope, J. C. W. & Ebbestad, J. O. (2024). Tergomyan molluscs from the Early Ordovician of the Llangynog Inlier, South Wales, UK. Palaeontologische Zeitschrift, 98(1), 17-28
Open this publication in new window or tab >>Tergomyan molluscs from the Early Ordovician of the Llangynog Inlier, South Wales, UK
2024 (English)In: Palaeontologische Zeitschrift, ISSN 0031-0220, E-ISSN 1867-6812, Vol. 98, no 1, p. 17-28Article in journal (Refereed) Published
Abstract [en]

A low abundance but diverse fauna of tergomyan molluscs is described from the Llangynog Inlier, Carmarthenshire, South Wales. The specimens originate from a single quarry exposing shallow-water siltstone and mudstone beds of the Early Arenig (early Floian) Bolahaul Member of the Ogof Hen Formation. The fauna includes Proplina areniga sp. nov., Proplina? obtusa sp. nov., Celtopileus calvapex gen. et sp. nov. with preserved muscle scars, Costulaconus mirificus gen. et sp. nov., and Hypseloconus? sp. Comparable tryblidiid taxa are mainly found in the Lower Ordovician of Midwestern USA among species of Proplina Kobayashi, 1933 and Gasconadeoconus Stinchcomb, 1986. The tentative assignment of the predominantly late Cambrian Hypseloconus is symptomatic of the many uncertainties regarding the phylogeny of the tryblidiids. The diverse assemblage of organisms preserved at the single locality represents one of the most remarkable faunas of this age worldwide.

Place, publisher, year, edition, pages
Springer, 2024
Keywords
Mollusca, Tergomya, Early Arenig, Early Floian, South Wales
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-528274 (URN)10.1007/s12542-023-00667-5 (DOI)001060010000002 ()
Available from: 2024-05-20 Created: 2024-05-20 Last updated: 2024-05-20Bibliographically approved
Hoyberget, M., Ebbestad, J. O., Funke, B., Funke, M.-L. K. & Nakrem, H. A. (2023). The Skyberg Lagerstatte from the Mjosa area, Norway: a rare window into the late early Cambrian biodiversity of Scandinavia. Lethaia: an international journal of palaeontology and stratigraphy, 56(2), 1-28
Open this publication in new window or tab >>The Skyberg Lagerstatte from the Mjosa area, Norway: a rare window into the late early Cambrian biodiversity of Scandinavia
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2023 (English)In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 56, no 2, p. 1-28Article in journal (Refereed) Published
Abstract [en]

The Skyberg Biota is a new early Cambrian Konservat-Lagerstatte, documented from a 7.5-m-thick succession of the Skyberg Member, Ringstranda Formation, in the classical Mjosa area of Norway. It displays a high species diversity and contains: algae; sponges; brachiopods; hyoliths; bivalved arthropods; trilobites; palaeoscolecids and other vermiform organisms; weakly sclerotized fragments of unknown affinity; several tubicolous fossils; the enigmatic genus Lapworthella; and a number of additional problematica together with infrequent trace fossils consisting of burrows and faecal pellets. This novel macro-biota encloses the most diverse fossil assemblage known from the Cambrian Series 2 locally in the Mjosa area, and regionally in Baltoscandia, and currently includes around 50 species of 10 major animal groups and macro-algae. The Skyberg Biota contains taxa previously unknown from Norway, several are new to Baltoscandia and also includes a range of new species. The Skyberg biota offers a rare glimpse into the biodiversity of Baltoscandia just prior to the large faunal turnover at the late-middle Cambrian transition.

Place, publisher, year, edition, pages
Scandinavian University Press / Universitetsforlaget AS, 2023
Keywords
Cambrian stage 4, ringstranda formation, konservat-lagerstätte, shelly fossils, algae, biodiversity, problematica
National Category
Geology Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-506966 (URN)10.18261/let.56.2.4 (DOI)001003178800002 ()
Available from: 2023-07-04 Created: 2023-07-04 Last updated: 2023-07-04Bibliographically approved
Streng, M., Høyberget, M. & Ebbestad, J. O. (2022). Bradoriids from the late early Cambrian of Norway and Sweden. In: Jeanette Bergman Weihed; Åke Johansson; Emma Rehnström (Ed.), Geological Society of Sweden, 150 year anniversary meeting: Uppsala, August 17–19, 2022: Abstract volume. Paper presented at Geological Society of Sweden, 150 year anniversary meeting, Uppsala, August 17–19, 2022 (pp. 342-343). Geologiska föreningen
Open this publication in new window or tab >>Bradoriids from the late early Cambrian of Norway and Sweden
2022 (English)In: Geological Society of Sweden, 150 year anniversary meeting: Uppsala, August 17–19, 2022: Abstract volume / [ed] Jeanette Bergman Weihed; Åke Johansson; Emma Rehnström, Geologiska föreningen , 2022, p. 342-343Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

A new bradoriid fauna comprising seven taxa is introduced from the early Cambrian Skyberg Member of the Ringstrand Formation of the Mjøsa area in Norway. The fauna is compared to coeval specimens described from Sweden (Wiman 1903), which have been restudied for this study. Both faunas comprise the same, or similar, genera of the families Bradoriidae, Beyrichonidae, Hipponicharionidae, and Svealutidae. Reevaluation of Wiman’s specimens revealed the presence of five distinct taxa rather than nine. The faunas from Norway and Sweden are similar to contemporaneous faunas of Avalonia and West Gondwana.

Place, publisher, year, edition, pages
Geologiska föreningen, 2022
Series
Geologiska Föreningen Specialpublikation ; 1
Keywords
Cambrian, Skyberg, bradoriids, Sweden, Norway, Taxonomy
National Category
Geology Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-505776 (URN)978-91-987833-0-8 (ISBN)
Conference
Geological Society of Sweden, 150 year anniversary meeting, Uppsala, August 17–19, 2022
Available from: 2023-06-21 Created: 2023-06-21 Last updated: 2023-06-21Bibliographically approved
Ebbestad, J. O., Hybertsen, F., Hogstrom, A. E. S., Jensen, S., Palacios, T., Taylor, W. L., . . . Meinhold, G. (2022). Distribution and correlation of Sabellidites cambriensis (Annelida?) in the basal Cambrian on Baltica. Geological Magazine, 159(7), 1262-1283, Article ID PII S0016756821001187.
Open this publication in new window or tab >>Distribution and correlation of Sabellidites cambriensis (Annelida?) in the basal Cambrian on Baltica
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2022 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 159, no 7, p. 1262-1283, article id PII S0016756821001187Article in journal (Refereed) Published
Abstract [en]

Sabellidites cambriensis is a tubular non-mineralized metazoan that appears as compressed ribbon-shaped imprints with transverse wrinkling, thick walls and an even tube diameter of up to 3 mm. The distribution of Sabellidites is investigated in three Ediacaran-Cambrian sections on the Digermulen Peninsula in Arctic Norway, spanning the Manndrapselva Member of the Stahpogieddi Formation and the lower member of the Breidvika Formation. Here, the Ediacaran-Cambrian boundary is located in the lower part of the upper parasequence (third cycle) of the Manndrapselva Member. Specimens of Sabellidites are rare but consistently present close to the lowest level of Treptichnus pedum and upsection, whereas the taxon is common and abundant in the lower part of the lower member of the Breidvika Formation, with an upper record at c. 55 m above the base. The range is comparable with that of the GSSP section in Newfoundland, Canada, establishing Sabellidites as an index fossil for the lowermost Cambrian. In the Manndrapselva Member, Sabellidites co-occurs with the acritarch Granomarginata, indicative of the lowermost Cambrian Granomarginata Zone, whereas in the Breidvika Formation it co-occurs with Asteridium. Sabellidites is widely distributed in Baltica, through the Rovnian and Lontovan regional stages but confined to the Fortunian global stage. In its lower range, Sabellidites is associated with a Treptichnus pedum trace fossil association and a depauperate leiosphaerid acritarch assemblage, followed by a Granomarginata assemblage. In its upper range, Sabellidites co-occurs with acritarchs of the Asteridium-Comasphaeridium Zone and the tubular foraminiferan Platysolenites. In Baltica, Sabellidites is a useful index fossil.

Place, publisher, year, edition, pages
Cambridge University PressCambridge University Press (CUP), 2022
Keywords
Sabellidites, Ediacaran-Cambrian boundary, biostratigraphy, correlation, Baltica, East European Platform
National Category
Other Earth and Related Environmental Sciences Geology
Identifiers
urn:nbn:se:uu:diva-485019 (URN)10.1017/S0016756821001187 (DOI)000728500800001 ()
Available from: 2022-09-22 Created: 2022-09-22 Last updated: 2024-01-15Bibliographically approved
Streng, M., Rasmussen, J. A., Ebbestad, J. O. & Weidner, T. (2022). First record of an Early Ordovician brachiopod and conodont fauna from Lapland, Sweden. GFF, 144(1), 24-40
Open this publication in new window or tab >>First record of an Early Ordovician brachiopod and conodont fauna from Lapland, Sweden
2022 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 144, no 1, p. 24-40Article in journal (Refereed) Published
Abstract [en]

An Early Ordovician fauna of linguliform brachiopods and euconodonts is described from the Alum Shale Formation in northernmost Vasterbotten County, northern Sweden. The fauna was recovered from a single carbonate concretion collected at an exposure near the northern shore of Lake Storvindeln. Despite of the fragmentary and tectonized preservation of the obtained fossils, at least eight different taxa of linguliform brachiopods and four species of euconodonts could be identified. Among the brachiopods, the ephippelasmatid Pomeraniotreta biernatae Bednarczyk, 1986 is most common; it is associated among others with the acrotretids Eurytreta cf. sabrinae (Callaway, 1877) and Ottenbyella sp., and a spinose specimen potentially representing the zhanatellid Thysanotos. Two of the brachiopod taxa appear to present new species, Pomeraniotreta n. sp. and Mytoella? n. sp., but additional material would be needed for a formal description. Euconodont specimens are rare and comprise coniform elements of Drepanodus arcuatus Pander, 1856, Drepanoistodus aff. amoenus (Lindstrom, 1955) sensu Lofgren (1994), Paroistodus numarcuatus (Lindstrom, 1955) and Rossodus aff. manitouensis Repetski & Ethington, 1983. Evaluation of the stratigraphic distribution of the different taxa of brachiopods and euconodonts under consideration of the local geology, suggests that the investigated sample represents a level in the upper part of the Tremadocian (Tr2) part of the Alum Shale Formation. The fauna represents the northernmost occurrence of age diagnostic Early Ordovician (Tremadocian) fossils in Sweden.

Place, publisher, year, edition, pages
Informa UK Limited, 2022
Keywords
Ordovician, Tremadocian, linguliform brachiopods, euconodonts, Lapland
National Category
Other Earth and Related Environmental Sciences Geology
Identifiers
urn:nbn:se:uu:diva-478573 (URN)10.1080/11035897.2022.2032822 (DOI)000808346000003 ()
Funder
Swedish Research Council, 621-2011-4961
Available from: 2022-06-28 Created: 2022-06-28 Last updated: 2022-06-28Bibliographically approved
Agic, H., Hogstrom, A. E. S., Jensen, S., Ebbestad, J. O., Vickers-Rich, P., Hall, M., . . . Taylor, W. L. (2022). Late Ediacaran occurrences of the organic-walled microfossils Granomarginata and flask-shaped Lagoenaforma collaris gen. et sp. nov.. Geological Magazine, 159(7), 1071-1092, Article ID PII S0016756821001096.
Open this publication in new window or tab >>Late Ediacaran occurrences of the organic-walled microfossils Granomarginata and flask-shaped Lagoenaforma collaris gen. et sp. nov.
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2022 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 159, no 7, p. 1071-1092, article id PII S0016756821001096Article in journal (Refereed) Published
Abstract [en]

New occurrences of flask-shaped and envelope-bearing microfossils, including the predominantly Cambrian taxon Granomarginata, are reported from new localities, as well as from earlier in time (Ediacaran) than previously known. The stratigraphic range of Granomarginata extends into the Cambrian System, where it had a cosmopolitan distribution. This newly reported Ediacaran record includes areas from Norway (Baltica), Newfoundland (Avalonia) and Namibia (adjacent to the Kalahari Craton), and puts the oldest global occurrence of Granomarginata in the Indreelva Member (< 563 Ma) of the Stahpogieddi Formation on the Digermulen Peninsula, Arctic Norway. Although Granomarginata is rare within the assemblage, these new occurrences together with previously reported occurrences from India and Poland, suggest a potentially widespread palaeogeographic distribution of Granomarginata through the middle-late Ediacaran interval. A new flask-shaped microfossil Lagoenaforma collaris gen. et sp. nov. is also reported in horizons containing Granomarginata from the Stahpogieddi Formation in Norway and the Dabis Formation in Namibia, and flask-shaped fossils are also found in the Gibbett Hill Formation in Newfoundland. The Granomarginata-Lagoenaforma association, in addition to a low-diversity organic-walled microfossil assemblage, occurs in the strata postdating the Shuram carbon isotope excursion, and may eventually be of use in terminal Ediacaran biostratigraphy. These older occurrences of Granomarginata add to a growing record of body fossil taxa spanning the Ediacaran-Cambrian boundary.

Place, publisher, year, edition, pages
Cambridge University Press, 2022
Keywords
organic-walled microfossils, biostratigraphy, Ediacaran, Cambrian
National Category
Geology Evolutionary Biology Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-485446 (URN)10.1017/S0016756821001096 (DOI)000767087900001 ()
Funder
Swedish Research Council, VR2016-06810
Available from: 2022-10-03 Created: 2022-10-03 Last updated: 2022-10-03Bibliographically approved
Palacios, T., Hogstrom, A. E. S., Jensen, S., Ebbestad, J. O., Agi, H., Hoyberget, M., . . . Taylor, W. L. (2022). Organic-walled microfossils from the Kistedalen Formation, Norway: acritarch chronostratigraphy of the Baltic Miaolingian and evolutionary trends of placoid acritarchs. Papers in Palaeontology, 8(4), Article ID e1457.
Open this publication in new window or tab >>Organic-walled microfossils from the Kistedalen Formation, Norway: acritarch chronostratigraphy of the Baltic Miaolingian and evolutionary trends of placoid acritarchs
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2022 (English)In: Papers in Palaeontology, ISSN 2056-2799, E-ISSN 2056-2802, Vol. 8, no 4, article id e1457Article in journal (Refereed) Published
Abstract [en]

New acritarch data from the Kistedalen Formation based on two sections with continuous exposure enable us to establish the most detailed Miaolingian acritarch biozonation in Baltica to date. Six interval zones previously established in Gondwana, the Eliasum llaniscum, Cristallinium cambriense, Adara alea, Timofeevia lancarae, Cristallinium dubium and Vulcanisphaera turbata zones, are identified, and their correlations within the Acado-Baltic Province examined. The diagnoses of Retisphaeridium, Cristallinium, Retisphaeridium dichamerum, Retisphaeridium lechistanium, Cristallinium dubium and Cristallinium cambriense are emended and the new species Retisphaeridium rugulatum sp. nov. and Retisphaeridium minimum sp. nov. are described. The diagnosis of Retisphaeridium ovillense (Cramer & Diez) Vanguestaine is emended and the species assigned to Dictyotidium ovillense comb. nov. The main evolutionary changes of the placoid acritarchs during the Miaolingian are analysed. Comparison with previous acritarch data from the Kistedalen Formation suggests that different extraction methodologies may result in significant bias in the recovered fossil record.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
acritarch, Miaolingian, chronostratigraphy, evolution, global correlation, Norway
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-495153 (URN)10.1002/spp2.1457 (DOI)000844814500001 ()
Available from: 2023-01-31 Created: 2023-01-31 Last updated: 2023-04-14Bibliographically approved
Meinhold, G., Willbold, M., Karius, V., Jensen, S., Agic, H., Ebbestad, J. O., . . . Taylor, W. L. (2022). Rare earth elements and neodymium and strontium isotopic constraints on provenance switch and post-depositional alteration of fossiliferous Ediacaran and lowermost Cambrian strata from Arctic Norway. Precambrian Research, 381, Article ID 106845.
Open this publication in new window or tab >>Rare earth elements and neodymium and strontium isotopic constraints on provenance switch and post-depositional alteration of fossiliferous Ediacaran and lowermost Cambrian strata from Arctic Norway
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2022 (English)In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 381, article id 106845Article in journal (Refereed) Published
Abstract [en]

The Digermulen Peninsula in northeastern Finnmark, Arctic Norway, comprises one of the most complete Ediacaran-Cambrian transitions worldwide with a nearly continuous record of micro-and macrofossils from the interval of the diversification of complex life. Here, we report on the provenance and post-depositional alteration of argillaceous mudstones from the Digermulen Peninsula using rare earth elements and Sm-Nd and Rb-Sr isotopic systematics to provide an environmental context and better understand this important transition in Earth's history. The studied sections comprise a mid-Ediacaran glacial-interglacial cycle, including the Nyborg Formation (ca. 590 Ma) and Mortensnes Formation (related to the ca. 580 Ma-old Gaskiers glaciation), and the St & PRIME;ahpogieddi Formation (ca. 560-537 Ma), which yields Ediacara-type fossils in the Indreelva Member and contains the Ediacaran-Cambrian boundary interval in the Manndrapselva Member and basal part of the informal Lower Breidvika member (ca. 537-530 Ma). Three sample groups, (1) Nyborg and Mortensnes for-mations, (2) the lowermost five samples from the Indreelva Member and (3) the remaining samples from the Indreelva as well as from the Manndrapselva and Lower Breidvika members, can be distinguished, belonging to distinct depositional units. All samples have negative epsilon(Nd)(T) values (-6.00 to -21.04) indicating a dominant input of terrigenous detritus with an old continental crust affinity. Significant shifts in Sm-Nd isotope values are related to changes in the sediment source, i.e. Svecofennian province vs Karelian province vs Svecofennian province plus in addition likely some juvenile (late Neoproterozoic volcanic) material, and probably reflect palaeotectonic reorganisation along the Iapetus-facing margin of Baltica. The combined Rb-Sr isotopic data of all samples yield an errorchron age of about 430 Ma reflecting the resetting of the Rb-Sr whole-rock isotope systems of the mudstones during the Scandian tectono-metamorphic event in the Gaissa Nappe Complex of Finnmark. Preservation of palaeopascichnids coincides with the sedimentation regimes of sample groups 2 and 3 while other Ediacara-type fossils, e.g. Aspidella-type and frondose forms, are limited to the sample group 3. Our results are similar to those of earlier studies from the East European Platform in suggesting oxic seafloor conditions during the late Ediacaran.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Vestertana Group, Sediment provenance, Rare earth elements, Rb-Sr, Sm-Nd, Scandinavia
National Category
Other Earth and Related Environmental Sciences Geology
Identifiers
urn:nbn:se:uu:diva-492235 (URN)10.1016/j.precamres.2022.106845 (DOI)000890947800001 ()
Funder
Swedish Research Council, VR2016-06810The Research Council of Norway, 231103
Available from: 2023-01-03 Created: 2023-01-03 Last updated: 2023-01-03Bibliographically approved
Ebbestad, J. O., Cederstrom, P. & Peel, J. S. (2022). Shell injuries, repair and malformation in the early Cambrian mollusc Helcionella antiqua from Scania, Sweden. GFF, 144(3-4), 203-209
Open this publication in new window or tab >>Shell injuries, repair and malformation in the early Cambrian mollusc Helcionella antiqua from Scania, Sweden
2022 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 144, no 3-4, p. 203-209Article in journal (Refereed) Published
Abstract [en]

Three cases of repaired injuries and malformation in specimens of the helcionelloid mollusc Helcionella antiqua (Ki & UAELIG;r, 1917) from the lower Cambrian (Cambrian Series 2, Stage 4) Gislov Formation of southern Sweden document some of the oldest known durophagous attacks on Palaeozoic molluscs. Two of the injuries are developed as clefts, of which one had a severe effect on the continued growth of the shell. The third example is a large embayment removing large portions of the supra-apical part of the shell. A similar repaired injury is known in the slightly older mollusc Marocella mira Geyer, 1986. from Antarctica and Australia. The morphology of the injuries and the hydrodynamically quiet depositional setting suggests that the shell damage was caused by failed predatory attacks. The location of the repaired injuries suggests that the attacks may have targeted the head region of the molluscs, thus supporting an endogastrically coiled orientation of the shell in Helcionella. Only three repaired injuries in 252 Helcionella specimens were found, giving a shell repair frequency of 1.2%. All three examples occur in the larger size classes. The size-frequency distribution (N = 182) is strongly right skewed, which could suggest high input of juvenile specimens into the assemblage. The assemblage is interpreted as a time averaged and mixed death assemblage, albeit with good correspondence with the living shelly assemblage, due to a relatively thin, homogenous unit that may suggest within-habitat time averaging.

Place, publisher, year, edition, pages
Taylor & Francis, 2022
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-522427 (URN)10.1080/11035897.2023.2233571 (DOI)001044932400001 ()
Available from: 2024-02-07 Created: 2024-02-07 Last updated: 2024-02-07Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-8769-3572

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