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En mellanjurassisk flora från Bagå-formationen, Bornholm

Mehlqvist, Kristina (2008) In Examensarbeten i geologi vid Lunds universitet
Department of Geology
Abstract (Swedish)
En samling växtfossil från Bagå-formationen, Bornholm, Danmark, har undersökts för att identifiera
sammansättningen av floran samt tolka klimatet. Sedimenten som utgör Bagå-formationen deponerades under
mellanjura mellan den danska bassängen och det polska tråget och består av lersten med mellanlagrande kolskikt.
Depositionsmiljön har tolkats som ett meandrande flodsystem med stora torvbildande träskmarker i anslutning till
flodområdet.
Sedimenten innehåller mycket välbevarade avtryck och kompressioner av växter och materialet som ingår i denna
studie insamlades av bl.a. Möller (1902) och materialet finns registrerat i samlingarna vid Geologiska institutionen
vid Lunds universitet. Fossilen delades in i sju släkten varav bara två... (More)
En samling växtfossil från Bagå-formationen, Bornholm, Danmark, har undersökts för att identifiera
sammansättningen av floran samt tolka klimatet. Sedimenten som utgör Bagå-formationen deponerades under
mellanjura mellan den danska bassängen och det polska tråget och består av lersten med mellanlagrande kolskikt.
Depositionsmiljön har tolkats som ett meandrande flodsystem med stora torvbildande träskmarker i anslutning till
flodområdet.
Sedimenten innehåller mycket välbevarade avtryck och kompressioner av växter och materialet som ingår i denna
studie insamlades av bl.a. Möller (1902) och materialet finns registrerat i samlingarna vid Geologiska institutionen
vid Lunds universitet. Fossilen delades in i sju släkten varav bara två exemplar till artnivå. Den fossila floran
domineras av ormbunkar men innehåller även Ginkgoales, barrträd, bennettiter och fräken. Jämförelser med likåldriga
floror visar att sammansättningen i Bagåsamlingen liknar den jurassiska Eriksdalsfloran från Skåne.
Juratiden var en varm och fuktig period och fem biom har identifierats globalt. Floran i denna studie tolkas som
förekommande i ett varmtempererat biom (i ett varmt och fuktigt klimat).
Prover av kutikula (det yttersta vaxartade lagret hos blad) härrörande från fossila barrtäd av arten Bilsdalea angustifolia
från Bagå-formationen studerades med avseende på stomatadensitet för att utvärdera olika beräkningssätt
och metoder för tolkning av temperatur och paleo-CO2 halter. Resultaten blev olika beroende på vilken del av bladet
som räknades och i allmänhet gav resultaten låga koldioxidhalter. Mer omfattande studier krävs för att förbättra
tekniken för användning av smalbladiga pre-angiosperma floror. (Less)
Abstract
A collection of plant fossils from the Bagå Formation, Bornholm, Denmark, has been investigated to
identify the composition of the flora and interpret the climate. The sediments of the Bagå Formation were deposited
during the Middle Jurassic between the Danish basin and the Polish through and consist of mudstone interbedded
with coal seams. The depositional environment has been interpreted as a meandering fluvial system hosting extensive
peatforming marshes in flood-basin areas.
The sediments contain well-preserved plant impressions and compressions and the material investigated in this
study was collected, among others, by Möller in 1902 and is registered in the collections at the Geological Department,
Lund University. The fossils... (More)
A collection of plant fossils from the Bagå Formation, Bornholm, Denmark, has been investigated to
identify the composition of the flora and interpret the climate. The sediments of the Bagå Formation were deposited
during the Middle Jurassic between the Danish basin and the Polish through and consist of mudstone interbedded
with coal seams. The depositional environment has been interpreted as a meandering fluvial system hosting extensive
peatforming marshes in flood-basin areas.
The sediments contain well-preserved plant impressions and compressions and the material investigated in this
study was collected, among others, by Möller in 1902 and is registered in the collections at the Geological Department,
Lund University. The fossils were assigned to seven plant genera but only two specimens were identified to
species level. The fossil flora is dominated by ferns but also contains Ginkgoales, conifers, Bennettitales and Equisetales.
Comparisons with coeval plant assemblages show that the flora from the Bagå Formation closely resembles
that of Eriksdal, Skåne.
The Jurassic was a warm and humid period and five biomes have been recognized across the globe. The flora
studied herein is interpreted to have grown in the warm temperate biome (in i.e. a warm and humid climate).
Additionally, samples of cuticle (the outer waxy coating of the leaf) derived from the conifer taxon Bilsdalea
angustifolia from the Bagå Formation were studied to evaluate different methods for counting stomata used in the
interpretation of palaeotemperature and the palaeo-CO2 levels. The results were different depending on which part
of the leaf was analyzed and low palaeo-CO2 levels were generally documented using previous methods. More,
extensive studies are required to refine this technique for use with predominantly narrow-leafed pre-angiosperm
floras. (Less)
Please use this url to cite or link to this publication:
author
Mehlqvist, Kristina
supervisor
organization
alternative title
A middle Jurassic flora from the Bagå Formation, Bornholm
year
type
M2 - Bachelor Degree
subject
keywords
Bagå, jura, flora, klimat, CO2, stomata, Jurassic, climate
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
227
language
Swedish
id
2303861
date added to LUP
2012-01-30 11:54:09
date last changed
2012-01-30 11:54:09
@misc{2303861,
  abstract     = {A collection of plant fossils from the Bagå Formation, Bornholm, Denmark, has been investigated to
identify the composition of the flora and interpret the climate. The sediments of the Bagå Formation were deposited
during the Middle Jurassic between the Danish basin and the Polish through and consist of mudstone interbedded
with coal seams. The depositional environment has been interpreted as a meandering fluvial system hosting extensive
peatforming marshes in flood-basin areas.
The sediments contain well-preserved plant impressions and compressions and the material investigated in this
study was collected, among others, by Möller in 1902 and is registered in the collections at the Geological Department,
Lund University. The fossils were assigned to seven plant genera but only two specimens were identified to
species level. The fossil flora is dominated by ferns but also contains Ginkgoales, conifers, Bennettitales and Equisetales.
Comparisons with coeval plant assemblages show that the flora from the Bagå Formation closely resembles
that of Eriksdal, Skåne.
The Jurassic was a warm and humid period and five biomes have been recognized across the globe. The flora
studied herein is interpreted to have grown in the warm temperate biome (in i.e. a warm and humid climate).
Additionally, samples of cuticle (the outer waxy coating of the leaf) derived from the conifer taxon Bilsdalea
angustifolia from the Bagå Formation were studied to evaluate different methods for counting stomata used in the
interpretation of palaeotemperature and the palaeo-CO2 levels. The results were different depending on which part
of the leaf was analyzed and low palaeo-CO2 levels were generally documented using previous methods. More,
extensive studies are required to refine this technique for use with predominantly narrow-leafed pre-angiosperm
floras.},
  author       = {Mehlqvist, Kristina},
  keyword      = {Bagå,jura,flora,klimat,CO2,stomata,Jurassic,climate},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {En mellanjurassisk flora från Bagå-formationen, Bornholm},
  year         = {2008},
}