En detaljerad undersökning av den mellanordoviciska ”furudalkalkstenen” i Dalarna
(2021) In Examensarbeten i geologi vid Lunds universitet GEOL01 20211Department of Geology
- Abstract (Swedish)
- Under sen darriwil-tid i mellanordovicium var Baltica täckt av ett grundhav med relativt rikt och varierat djurliv. Under årmiljoner avsattes här sediment som kom att omvandlas till kompakta kallvattens-karbonater. Baserat på fältstudier och punkträkning av sex stycken tunnslip har den omkring 10 meter mäktiga ”furudalkalkstenen” vid Kårgärdeprofilen (Dalarna, Sverige) analyserats med avseende på mikrofacies och fossilinnehåll. Detta ger ledtrådar till hur bottenmiljön och vattendjupet varierade över tid, och en god bild av förändringarna i fauna och bottensubstrat i Dalarna under tiden som bergenheten avsattes. Resultaten ger vidare möjligheter att jämföra miljöförhållanden mellan olika delar av den baltoskandiska bassängen under... (More)
- Under sen darriwil-tid i mellanordovicium var Baltica täckt av ett grundhav med relativt rikt och varierat djurliv. Under årmiljoner avsattes här sediment som kom att omvandlas till kompakta kallvattens-karbonater. Baserat på fältstudier och punkträkning av sex stycken tunnslip har den omkring 10 meter mäktiga ”furudalkalkstenen” vid Kårgärdeprofilen (Dalarna, Sverige) analyserats med avseende på mikrofacies och fossilinnehåll. Detta ger ledtrådar till hur bottenmiljön och vattendjupet varierade över tid, och en god bild av förändringarna i fauna och bottensubstrat i Dalarna under tiden som bergenheten avsattes. Resultaten ger vidare möjligheter att jämföra miljöförhållanden mellan olika delar av den baltoskandiska bassängen under mellanordovicium – exempelvis i Västergötland och på Öland där karbonater från samma tidsintervall finns bevarade. Inom ”furudalkalkstenen” dokumenteras här en svag trend uppåt mot en grundare vattenmiljö med mer varierad fauna. Avsaknaden av påtagliga förändringar i litologin tyder på att avsättningsmiljön var mer stabil i Dalarna än i södra Sverige vid samma tid. Denna skillnad innebär att bottenmiljön i Dalarna påverkades relativt lite av havsnivå- och miljöförändringar, sannolikt på grund av en mer distal position i den baltoskandiska bassängen och/eller att området hade bättre kontakt med stabila oceaniska vattenförhållanden. (Less)
- Abstract
- During the late Darriwilian age (Middle Ordovician) Baltica was covered by a shallow, epeiric sea with a fairly rich and varied fauna. Over millions of years, carbonate sediment was deposited that later transformed into compact cool-water limestone. Based on field studies and point-counting of six thin sections, the ca 10 meter thick ‘Furudal Limestone’ at the locality Kårgärde (Dalarna, Sweden) has been analysed regarding microfacies and fossil content, providing clues about how the benthic environment and water depth varied through time. The study also gives an overview of how both fauna and benthic substrate changed during the time that the ‘Furudal Limestone’ was deposited. Moreover, the collected data provides opportunities to compare... (More)
- During the late Darriwilian age (Middle Ordovician) Baltica was covered by a shallow, epeiric sea with a fairly rich and varied fauna. Over millions of years, carbonate sediment was deposited that later transformed into compact cool-water limestone. Based on field studies and point-counting of six thin sections, the ca 10 meter thick ‘Furudal Limestone’ at the locality Kårgärde (Dalarna, Sweden) has been analysed regarding microfacies and fossil content, providing clues about how the benthic environment and water depth varied through time. The study also gives an overview of how both fauna and benthic substrate changed during the time that the ‘Furudal Limestone’ was deposited. Moreover, the collected data provides opportunities to compare environments in different parts of the Baltoscandian basin during the mid-Ordovician, e.g. in Västergötland and at Öland, where carbonates from the same time interval are preserved. The ‘Furudal Limestone’ displays a weak shallowing-upward-trend along with a change to a slightly richer (more diverse) fauna. The lack of any substantial temporal changes in lithology suggests that the environment was more stable in Dalarna than in other parts of the basin during the same time interval. This implicates that the seafloor environment in Dalarna was relatively insensitive to sea level- and environmental changes, probably due to a more distal position in the Baltoscandian basin, and/or that the area was in better contact with stable oceanic conditions. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9064516
- author
- Granbom, Johanna LU
- supervisor
-
- Anders Lindskog LU
- Mats Eriksson LU
- organization
- course
- GEOL01 20211
- year
- 2021
- type
- M2 - Bachelor Degree
- subject
- keywords
- microfaciesanalys, kallvattenskarbonater, baltoskandiska faciesbälten, Siljansringen, mellanordovicium, microfacies analysis, cool-water carbonates, Baltoscandian confacies belts, Middle Ordovician
- publication/series
- Examensarbeten i geologi vid Lunds universitet
- report number
- 615
- language
- Swedish
- id
- 9064516
- date added to LUP
- 2021-09-01 15:41:13
- date last changed
- 2021-09-01 15:41:13
@misc{9064516,
abstract = {{During the late Darriwilian age (Middle Ordovician) Baltica was covered by a shallow, epeiric sea with a fairly rich and varied fauna. Over millions of years, carbonate sediment was deposited that later transformed into compact cool-water limestone. Based on field studies and point-counting of six thin sections, the ca 10 meter thick ‘Furudal Limestone’ at the locality Kårgärde (Dalarna, Sweden) has been analysed regarding microfacies and fossil content, providing clues about how the benthic environment and water depth varied through time. The study also gives an overview of how both fauna and benthic substrate changed during the time that the ‘Furudal Limestone’ was deposited. Moreover, the collected data provides opportunities to compare environments in different parts of the Baltoscandian basin during the mid-Ordovician, e.g. in Västergötland and at Öland, where carbonates from the same time interval are preserved. The ‘Furudal Limestone’ displays a weak shallowing-upward-trend along with a change to a slightly richer (more diverse) fauna. The lack of any substantial temporal changes in lithology suggests that the environment was more stable in Dalarna than in other parts of the basin during the same time interval. This implicates that the seafloor environment in Dalarna was relatively insensitive to sea level- and environmental changes, probably due to a more distal position in the Baltoscandian basin, and/or that the area was in better contact with stable oceanic conditions.}},
author = {{Granbom, Johanna}},
language = {{swe}},
note = {{Student Paper}},
series = {{Examensarbeten i geologi vid Lunds universitet}},
title = {{En detaljerad undersökning av den mellanordoviciska ”furudalkalkstenen” i Dalarna}},
year = {{2021}},
}