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Microscopic echinoderm remains from the Darriwilian (Middle Ordovician) of Västergötland, Sweden - faunal composition and applicability as environmental proxies

Kall, Christoffer LU (2014) In Dissertations in Geology at Lund University GEOL01 20141
Department of Geology
Abstract (Swedish)
Mikroskopiska echinodermfossil har undersökts ur prover från täljstensintervallet och intillig-gande delar av ’lanna’- och ’holenkalkstenen’ i Hällekis stenbrott, Västergötland. Den undersökta sektionen är från översta volkhov och mellersta kunda, darriwilian (mellanordovicium). Tidigare studier har konkluderat att en regression/transgression skedde under den undersökta perioden, vilket bekräftas av en kraftigt förhöjd echinoder-mabundans såväl som skenbar biodiversititet (baserad på morfotyper) i samband med de lägsta havsnivåerna. Abundansen sjunker efter täljstensintervallet, medan den skenbara biodiversiteten är fortsatt hög. De olika identifie-rade morfotyperna indikerar att mikroechinodermfaunan domineras av pelmatozoer, främst... (More)
Mikroskopiska echinodermfossil har undersökts ur prover från täljstensintervallet och intillig-gande delar av ’lanna’- och ’holenkalkstenen’ i Hällekis stenbrott, Västergötland. Den undersökta sektionen är från översta volkhov och mellersta kunda, darriwilian (mellanordovicium). Tidigare studier har konkluderat att en regression/transgression skedde under den undersökta perioden, vilket bekräftas av en kraftigt förhöjd echinoder-mabundans såväl som skenbar biodiversititet (baserad på morfotyper) i samband med de lägsta havsnivåerna. Abundansen sjunker efter täljstensintervallet, medan den skenbara biodiversiteten är fortsatt hög. De olika identifie-rade morfotyperna indikerar att mikroechinodermfaunan domineras av pelmatozoer, främst crinoidéer och cystoidéer, vilket delvis avspeglas på makroskopisk skala i form av massförekomster av cystoidéer. Några av de utplockade exemplaren uppvisar egenskaper vanliga bland holothurier, vilka då skulle vara de äldsta kända. Fort-satta studier krävs för att avgöra om så är fallet. (Less)
Abstract
Microscopic echinoderms were studied in acid-insoluble residues from the Lanna and Holen limestones at Hällekis, Västergötland, Sweden. The section studied spans the uppermost Volkhov and lower–middle Kunda Baltoscandian stages, within the Darriwillian global Stage (Middle Ordovician). The echinoderms show an increase in abundance, accompanying falling sea levels during the well-recognized regression initiated in the lower part of the so-called Täljsten interval. The echinoderm abundance reaches its maximum in connection to the lowest water depths, and decreases afterwards. Seven different morphotypes were defined and used to describe fluctuations in ostensive bio-diversity. The number of morphotypes present generally follows the same... (More)
Microscopic echinoderms were studied in acid-insoluble residues from the Lanna and Holen limestones at Hällekis, Västergötland, Sweden. The section studied spans the uppermost Volkhov and lower–middle Kunda Baltoscandian stages, within the Darriwillian global Stage (Middle Ordovician). The echinoderms show an increase in abundance, accompanying falling sea levels during the well-recognized regression initiated in the lower part of the so-called Täljsten interval. The echinoderm abundance reaches its maximum in connection to the lowest water depths, and decreases afterwards. Seven different morphotypes were defined and used to describe fluctuations in ostensive bio-diversity. The number of morphotypes present generally follows the same pattern as observed in abundance, until after the lowstand where the number of occurring morphotypes remains high, whereas the abundance decreases. The different morphotypes identified are indicative of an echinoderm fauna dominated by pelmatozoans, mainly crinoids and cystoids. This is partly mirrored at the macroscopic scale by the mass occurrence of cystoids in the ‘Täljsten’. Some of the microscopic echinoderms recovered exhibit features common only for holothurians. This would make these specimens the oldest fossil holothurians known thus far. (Less)
Please use this url to cite or link to this publication:
author
Kall, Christoffer LU
supervisor
organization
alternative title
Mellanordoviciska mikroechinodermer från Västergötland, Sverige - fauunasammansättning och lämplighet som proxy för miljöförändringar
course
GEOL01 20141
year
type
M2 - Bachelor Degree
subject
keywords
holenkalksten, lannakalksten, ordovicium, mikroskopisk, echinodermer, sweden, täljsten, echinoderms, microscopic, proxy, ordovician, darriwilian, kunda, volkhov, baltoscandia, lanna limestone, holen limestone, hällekis
publication/series
Dissertations in Geology at Lund University
report number
403
language
English
id
4469528
date added to LUP
2014-06-24 15:57:12
date last changed
2016-06-18 04:06:57
@misc{4469528,
  abstract     = {{Microscopic echinoderms were studied in acid-insoluble residues from the Lanna and Holen limestones at Hällekis, Västergötland, Sweden. The section studied spans the uppermost Volkhov and lower–middle Kunda Baltoscandian stages, within the Darriwillian global Stage (Middle Ordovician). The echinoderms show an increase in abundance, accompanying falling sea levels during the well-recognized regression initiated in the lower part of the so-called Täljsten interval. The echinoderm abundance reaches its maximum in connection to the lowest water depths, and decreases afterwards. Seven different morphotypes were defined and used to describe fluctuations in ostensive bio-diversity. The number of morphotypes present generally follows the same pattern as observed in abundance, until after the lowstand where the number of occurring morphotypes remains high, whereas the abundance decreases. The different morphotypes identified are indicative of an echinoderm fauna dominated by pelmatozoans, mainly crinoids and cystoids. This is partly mirrored at the macroscopic scale by the mass occurrence of cystoids in the ‘Täljsten’. Some of the microscopic echinoderms recovered exhibit features common only for holothurians. This would make these specimens the oldest fossil holothurians known thus far.}},
  author       = {{Kall, Christoffer}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Microscopic echinoderm remains from the Darriwilian (Middle Ordovician) of Västergötland, Sweden - faunal composition and applicability as environmental proxies}},
  year         = {{2014}},
}