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A palynological study across the Ordovician Kinnekulle bentonite, Sweden

Nordas, Johan LU (2015) In Dissertations in Geology at Lund University GEOL01 20151
Department of Geology
Abstract
A palynological analysis across the Ordovician (Sandbian) Kinnekulle bentonites in south Central Sweden has been performed. The sedimentary successions were recovered from the Borenshult -1 drillcore in the Motala area, south central Sweden. The lithology is dominated by mudstones and two thick bentonite beds. Acritarchs dominate the palynological assemblage but a few chitinozoans and scolecodonts were encountered. The composition of acritarchs is stable throughout the core with the exception of the two consecutive top-most samples in which every morphological group diminishes and disappear except the sphaeromorph type. The acritarch abundance changes within the core, the earliest sample shows a steady state until it reaches the oldest... (More)
A palynological analysis across the Ordovician (Sandbian) Kinnekulle bentonites in south Central Sweden has been performed. The sedimentary successions were recovered from the Borenshult -1 drillcore in the Motala area, south central Sweden. The lithology is dominated by mudstones and two thick bentonite beds. Acritarchs dominate the palynological assemblage but a few chitinozoans and scolecodonts were encountered. The composition of acritarchs is stable throughout the core with the exception of the two consecutive top-most samples in which every morphological group diminishes and disappear except the sphaeromorph type. The acritarch abundance changes within the core, the earliest sample shows a steady state until it reaches the oldest bentonite layer. At this point the acritarch abundance decrease rapidly and then recovers. In the period between the bentonite layers a higher abundance is recorded. In the second layer, the signature seen in the first layer is repeated. An upswing in acritarch abundance yet again occur in the layers resting on the bentonite. In the top-most layers of the core, the acritarchs almost disappear. The scolecodonts and chitinozoans occur only in very low abundance throughout the core. The acritarchs were counted and divided into functional traits depending on their morphology based on the visual traits of the processes. The biomass density is lower in the bentonite layers compared to the non-volcanic parts. Directly on top of both the bentonite beds an increase of acritarch abundance can be observed. The acritarch assemblage indicates a lowering of the sea-level at the topmost the samples. (Less)
Abstract (Swedish)
En palynologisk analys över Ordoviciums (Sandbian) Kinnekulle bentonit från södra delarna av mellersta Sverige har gjorts. Den sedimentära succsessionen är hämtad från Borenshult-1 borrkärnan som togs i Motala, syd-mellersta Sverige. Litologin domineras av mudstone och två tjocka bentonitlager. Akritarker dominerar den palynologiska sammansättningen och endast ett fåtal chitinozoer och scolecodonter kunde hittas. Kompositionen av akritarker är stabil igenom borrkärnan förutom i de två översta proverna där den sphaeromorpha gruppen är den enda morfologiska gruppen som inte minskar i andel och försvinner. Mängden akritarker förändras borrkärnan och i de tidigaste avlagringarna ser man ett ”steady-state” som bryts då det äldsta bentonitlagret... (More)
En palynologisk analys över Ordoviciums (Sandbian) Kinnekulle bentonit från södra delarna av mellersta Sverige har gjorts. Den sedimentära succsessionen är hämtad från Borenshult-1 borrkärnan som togs i Motala, syd-mellersta Sverige. Litologin domineras av mudstone och två tjocka bentonitlager. Akritarker dominerar den palynologiska sammansättningen och endast ett fåtal chitinozoer och scolecodonter kunde hittas. Kompositionen av akritarker är stabil igenom borrkärnan förutom i de två översta proverna där den sphaeromorpha gruppen är den enda morfologiska gruppen som inte minskar i andel och försvinner. Mängden akritarker förändras borrkärnan och i de tidigaste avlagringarna ser man ett ”steady-state” som bryts då det äldsta bentonitlagret nås. Då sker en snabb minskning i mängden akritarker som sedan hämtar sig. Mellan det äldre och yngre bentonitlagrena kan man se en större mängd akritarker. I det yngre bentonitlagret sker en upprepning av händelseförloppet som skedde i den äldre bentoniten. Efter bentoniten sker igen en ökning av andelen akritark men i de två översta proverna försvinner nästan hela akritarkgruppen. Scolecodonter och chitinozoer finns i endast låga mängder igenom hela borrkärnan. Akritarkerna räknades efter att ha delats in i funktionella grupper beroende på deras visuella morfologiska egenskaper. Biomassan är lägre i bentoniten i jämförelse med de icke-vulkaniska delarna och direkt ovanför båda bentonitlagrena kan man se en ökning av mängden akritarker. Förändringana i akritarksammansättningen pekar på att havsnivån sänks i det yngsta proverna. (Less)
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author
Nordas, Johan LU
supervisor
organization
course
GEOL01 20151
year
type
M2 - Bachelor Degree
subject
keywords
Acritarch, bentonite, Ordovician, Borenshult-1, Sweden, Kinnekulle
publication/series
Dissertations in Geology at Lund University
report number
449
language
English
id
5473081
date added to LUP
2015-09-15 16:58:07
date last changed
2016-09-14 04:08:18
@misc{5473081,
  abstract     = {A palynological analysis across the Ordovician (Sandbian) Kinnekulle bentonites in south Central Sweden has been performed. The sedimentary successions were recovered from the Borenshult -1 drillcore in the Motala area, south central Sweden. The lithology is dominated by mudstones and two thick bentonite beds. Acritarchs dominate the palynological assemblage but a few chitinozoans and scolecodonts were encountered. The composition of acritarchs is stable throughout the core with the exception of the two consecutive top-most samples in which every morphological group diminishes and disappear except the sphaeromorph type. The acritarch abundance changes within the core, the earliest sample shows a steady state until it reaches the oldest bentonite layer. At this point the acritarch abundance decrease rapidly and then recovers. In the period between the bentonite layers a higher abundance is recorded. In the second layer, the signature seen in the first layer is repeated. An upswing in acritarch abundance yet again occur in the layers resting on the bentonite. In the top-most layers of the core, the acritarchs almost disappear. The scolecodonts and chitinozoans occur only in very low abundance throughout the core. The acritarchs were counted and divided into functional traits depending on their morphology based on the visual traits of the processes. The biomass density is lower in the bentonite layers compared to the non-volcanic parts. Directly on top of both the bentonite beds an increase of acritarch abundance can be observed. The acritarch assemblage indicates a lowering of the sea-level at the topmost the samples.},
  author       = {Nordas, Johan},
  keyword      = {Acritarch,bentonite,Ordovician,Borenshult-1,Sweden,Kinnekulle},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {A palynological study across the Ordovician Kinnekulle bentonite, Sweden},
  year         = {2015},
}