Changes in beyrichiid ostracode faunas during the Late Silurian Lau Event on Gotland, Sweden
(2010) In Dissertations in Geology at Lund UniversityDepartment of Geology
- Abstract
- This paper deals with how palaeocope ostracodes of the family Beyrichiidae, from the Silurian strata at Gotland were affected by the Late Silurian Lau Event. The Lau Event is associated with a positive carbon isotope excursion, lithology changes and faunal changes in accumulated strata related to sea-level changes and a glaciation in the Late Ludlow. In order to find out how the beyrichiid faunas where affected by the event, fossils have been studied through samples collected from five different localities on Gotland, exposing pre-Lau Event, Lau Event, and post-Lau Event strata.A total of 633 beyrichiid specimens representing 22 different taxa were identified in the samples. Based on literature studies on the beyrichiid biostratigraphy on... (More)
- This paper deals with how palaeocope ostracodes of the family Beyrichiidae, from the Silurian strata at Gotland were affected by the Late Silurian Lau Event. The Lau Event is associated with a positive carbon isotope excursion, lithology changes and faunal changes in accumulated strata related to sea-level changes and a glaciation in the Late Ludlow. In order to find out how the beyrichiid faunas where affected by the event, fossils have been studied through samples collected from five different localities on Gotland, exposing pre-Lau Event, Lau Event, and post-Lau Event strata.A total of 633 beyrichiid specimens representing 22 different taxa were identified in the samples. Based on literature studies on the beyrichiid biostratigraphy on Gotland, an additional 15 taxa were included in this study, and an additional 27 localities. Subfamilies of Beyrichiidae treated herein are; Craspedobolbininae, Amphitoxotidinae, Treposellinae, Beyrichiinae and Hexophthalmoidinae. Except Hexophthalmoidinae, which disappears before the event, all subfamilies have been affected by the Lau Event. Several taxa were negatively affected, reported as e.g. 11 last appearance datums (LAD: s), four Lazarus taxa and three Lilliput taxa. Taxa that have been negatively affected by the Lau Event are e.g. Neobeyrichia (Neobeyrichia) lauensis and Neobeyrichia (Nodibeyrichia) scissa which occurs frequently in pre-event strata, but diminishes in frequency in middle event strata, to eventually disappear in upper event strata. The lineages of taxa such as Hemsiella anterovelata, Calcaribeyrichia bicalcarata, Hoburgiella tenerrima and Plicibeyrichia ornatissima have gaps through extensive portions of the event strata, and reappear again in post-event strata. Other taxa show a positive response to the event reflected by frequent occurrences and high abundances in relation to other taxa in the Lau Event strata. Neobeyrichia (Neobeyrichia) ctenophora occurs scarcely in pre-event strata, but is very frequent in event strata. The lineage of N. (Ne.) ctenophora continues into post-event strata where it is less frequent. Similarly, Hemsiella loensis and Sleia equestris occur frequently in event strata compared to many other taxa which are either rare, occur as Lazarus taxa or have their LAD: s in Lau Event strata. A recovery of the beyrichiid faunas is apparent in the Hamra Fm., where the fauna is characterized by a moderate diversity and with reappearing Lazarus species and Lilliput species that have recovered. Based on the faunal changes, it can be concluded that a re-organisation among beyrichiids did occur during the Lau Event. (Less)
- Abstract (Swedish)
- Den här uppsatsen behandlar hur palaeocopa ostrakodfossil av familjen Beyrichiidae, avsatta i sensilurisk lagerföljd på Gotland, påverkades av den så kallade Laukatastrofen som ägde rum i sen Ludlow. I lagerföljd avsatt under Laukatastrofen har bland annat anomalier i kolisotop, litologiförändringar och faunaförändringar påvisats, vilka är relaterade till globala havsnivåförändringar och en glaciation i sen Ludlow. För att ta reda på hur beyrichiidfaunan har påverkats av katastrofen, har prover insamlade från fem olika lokaler på Gotland studerats. För att jämföra den pre-katastrofa fanan, katastroffaunan och den post-katastrofa faunan, har proverna hämtats från lagerföljd avsatt innan-, under-, och efter Laukatastrofen. Totalt har 633... (More)
- Den här uppsatsen behandlar hur palaeocopa ostrakodfossil av familjen Beyrichiidae, avsatta i sensilurisk lagerföljd på Gotland, påverkades av den så kallade Laukatastrofen som ägde rum i sen Ludlow. I lagerföljd avsatt under Laukatastrofen har bland annat anomalier i kolisotop, litologiförändringar och faunaförändringar påvisats, vilka är relaterade till globala havsnivåförändringar och en glaciation i sen Ludlow. För att ta reda på hur beyrichiidfaunan har påverkats av katastrofen, har prover insamlade från fem olika lokaler på Gotland studerats. För att jämföra den pre-katastrofa fanan, katastroffaunan och den post-katastrofa faunan, har proverna hämtats från lagerföljd avsatt innan-, under-, och efter Laukatastrofen. Totalt har 633 beyrichiidfossil fördelat på 22 skilda taxa identifierats med hjälp av provmaterialet. Dock behandlas ytterligare 15 taxa baserat på litteraturstudier av beyrichiiders biostratigrafi på Gotland, och 27 övriga lokaler med pre-katastrof till post-katastrof fauna. Underfamiljer till Beyrichiidae, som har påträffats i det aktuella tidsintervallet är; Craspedobolbininae, Amphitoxotidinae, Treposellinae, Beyrichiinae and Hexophthalmoidinae. Med undantag för Hexophthalmoidinae som försvinner innan Laukatastrofen, har alla underfamiljer visat sig påverkas av katastrofen genom antingen utdöenden, Lazarustaxa eller Lilliputfaunor. I Laukatastrof lager har bland annat påträffats 11 utdöenden, fyra Lazarus faunor och tre Lilliput faunor. Exempel på taxa som påverkats negativt av katastrofen är Neobeyrichia (Neobeyrichia) lauensis och Neobeyrichia (Nodibeyrichia) scissa, vilka förekommer frekvent i lager avsatta innan Laukatastrofen, men vilka uppträder sällan i Laukatastroflager där båda arterna så småningom dör ut. Lazarusfaunor i Laukatastrof-lager har påvisats bland arterna Hemsiella anterovelata, Calcaribeyrichia bicalcarata, Hoburgiella tenerrima och Plicibeyrichia ornatissima. Viss taxa har gynnats positivt av katastrofen, då de dominerar markant över andra arter i fråga om frekvens eller abundans i lager avsatta under Laukatastrofen. Neobeyrichia (Neobeyrichia) ctenophora, Hemsiella loensis och Sleia equestris förekommer frekvent i katastroflager, i motsats till andar arter som förekommer mycket sällan eller dör ut i katastroflager. Vidare påträffas uppkomst av ny taxa i katastroflager. Utöver att S. equestris och H. loensis förekommer frekvent, förekommer också ett högt antal exemplar av arterna i prover hämtade från Laukatastrof-lager.En återhämtning av beyrichiidfaunan påvisas i post-katastrof lager där Lazarus-taxa återkommer, Lilliput faunor återhämtas och en mer varierad och stabil fauna förekommer. Baserat på förändringarna som påvisats bland de studerade beyrichiidarterna, kan det konstateras att det har skett en omorganisation av beyrichiidfaunan under Laukatastrofen. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/2295411
- author
- Rääf, Rebecka
- supervisor
- organization
- alternative title
- Förändringar i beyrichiida ostrakodfaunor under den sensiluriska Laukatastrofen på Gotland
- year
- 2010
- type
- H1 - Master's Degree (One Year)
- subject
- keywords
- Gotland, Late Silurian, Lau Event, ostracodes, Beyrichiidae, faunal turnovers, Sensilur, Laukatastrofen, ostrakoder, beyrichiider, faunaförändringar
- publication/series
- Dissertations in Geology at Lund University
- report number
- 264
- language
- English
- id
- 2295411
- date added to LUP
- 2012-02-07 10:31:03
- date last changed
- 2012-02-07 10:31:03
@misc{2295411,
abstract = {{This paper deals with how palaeocope ostracodes of the family Beyrichiidae, from the Silurian strata at Gotland were affected by the Late Silurian Lau Event. The Lau Event is associated with a positive carbon isotope excursion, lithology changes and faunal changes in accumulated strata related to sea-level changes and a glaciation in the Late Ludlow. In order to find out how the beyrichiid faunas where affected by the event, fossils have been studied through samples collected from five different localities on Gotland, exposing pre-Lau Event, Lau Event, and post-Lau Event strata.A total of 633 beyrichiid specimens representing 22 different taxa were identified in the samples. Based on literature studies on the beyrichiid biostratigraphy on Gotland, an additional 15 taxa were included in this study, and an additional 27 localities. Subfamilies of Beyrichiidae treated herein are; Craspedobolbininae, Amphitoxotidinae, Treposellinae, Beyrichiinae and Hexophthalmoidinae. Except Hexophthalmoidinae, which disappears before the event, all subfamilies have been affected by the Lau Event. Several taxa were negatively affected, reported as e.g. 11 last appearance datums (LAD: s), four Lazarus taxa and three Lilliput taxa. Taxa that have been negatively affected by the Lau Event are e.g. Neobeyrichia (Neobeyrichia) lauensis and Neobeyrichia (Nodibeyrichia) scissa which occurs frequently in pre-event strata, but diminishes in frequency in middle event strata, to eventually disappear in upper event strata. The lineages of taxa such as Hemsiella anterovelata, Calcaribeyrichia bicalcarata, Hoburgiella tenerrima and Plicibeyrichia ornatissima have gaps through extensive portions of the event strata, and reappear again in post-event strata. Other taxa show a positive response to the event reflected by frequent occurrences and high abundances in relation to other taxa in the Lau Event strata. Neobeyrichia (Neobeyrichia) ctenophora occurs scarcely in pre-event strata, but is very frequent in event strata. The lineage of N. (Ne.) ctenophora continues into post-event strata where it is less frequent. Similarly, Hemsiella loensis and Sleia equestris occur frequently in event strata compared to many other taxa which are either rare, occur as Lazarus taxa or have their LAD: s in Lau Event strata. A recovery of the beyrichiid faunas is apparent in the Hamra Fm., where the fauna is characterized by a moderate diversity and with reappearing Lazarus species and Lilliput species that have recovered. Based on the faunal changes, it can be concluded that a re-organisation among beyrichiids did occur during the Lau Event.}},
author = {{Rääf, Rebecka}},
language = {{eng}},
note = {{Student Paper}},
series = {{Dissertations in Geology at Lund University}},
title = {{Changes in beyrichiid ostracode faunas during the Late Silurian Lau Event on Gotland, Sweden}},
year = {{2010}},
}