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Stratigrafin i Hanöbukten under senaste glaciationen : en studie av borrkärnor från IODP’s expedition nr 347

Åberg, Gisela LU (2014) In Examensarbeten i geologi vid Lunds universitet GEOL01 20141
Department of Geology
Abstract
The development of Hanö Bay during the last ice age has been investigated by analyzing cores from IODP’s Balitc Sea Palaeoenvironment expedition in the Baltic Sea.
By analyzing the presence of Ice Rafted Debris, correlating one of the varved clay units to Ringbergs (1991)regional varve chronology from southeastern Sweden, analyzing pollen grains and measuring loss on ignition a few gaps in the history of Hanö Bay has been uncovered.
Four common units are found in the cores; a diamict unit, two varved clay units and an organic layer that separates the two varved clay units. The results from the analyzes, combined with the results from similar studies, show that the three lower units have been deposited after the Middle Weichselian... (More)
The development of Hanö Bay during the last ice age has been investigated by analyzing cores from IODP’s Balitc Sea Palaeoenvironment expedition in the Baltic Sea.
By analyzing the presence of Ice Rafted Debris, correlating one of the varved clay units to Ringbergs (1991)regional varve chronology from southeastern Sweden, analyzing pollen grains and measuring loss on ignition a few gaps in the history of Hanö Bay has been uncovered.
Four common units are found in the cores; a diamict unit, two varved clay units and an organic layer that separates the two varved clay units. The results from the analyzes, combined with the results from similar studies, show that the three lower units have been deposited after the Middle Weichselian Ristinge Ice Advance at approximately 60 ka BP. This is based partly on a former dating of unit 3, the organic layer, which showed an age of more than 38 ka. The varved clays are presumed to be deposited during glacial/interstadial conditions with a
proximal ice margin while the organic layer, unit 3, is supposed to have been deposited further away from the ice margin in an environment with some vegetation including herbs, grasses, shrubs and some trees. Unit 4 was correlated to Ringberg (1991) and was therefore dated to between 14 550 cal yr BP and 14 750 cal yr BP placing the unit during the Bølling interstadial. From this it was concluded that 25 ka is missing between units 3 and 4. This hiatus can be explained in different ways. It is, for example, possible that the Scandinavian ice sheet has eroded the unit during the Last Glacial Maximum, but there is also a possibility that no deposition took place during this time.
It was finally concluded that the younger geologic development of the Hanö Bay still is still not fully understood but that at least some of the earlier questions have been solved by these new results. (Less)
Abstract (Swedish)
Hanöbuktens utveckling under den senaste istiden har studerats med hjälp av borrkärnor från IODP’s Baltic Sea Palaeoenvironment expedition i Östersjön. Genom att analysera förekomsten av IRD, korrelera en varvig enhet till Ringbergs (1991) regionala lervarvskronologi från sydöstra Sverige, göra pollenanalyser och glödförlustbestämningar har en del luckor i Hanöbuktens historia fyllts i.
I borrkärnorna finns fyra gemensamma enheter; en diamikton, enhet 1, två varviga enheter, enhet 2 och 4 samt ett organiskt lager, enhet 3 som skiljer de båda varviga enheterna åt.
Resultaten från analyserna samt jämförelser med liknande studier visar att de tre undre enheterna är avsatta under och efter Ristingeframstöten för ca 60 000 kal år sedan. Detta... (More)
Hanöbuktens utveckling under den senaste istiden har studerats med hjälp av borrkärnor från IODP’s Baltic Sea Palaeoenvironment expedition i Östersjön. Genom att analysera förekomsten av IRD, korrelera en varvig enhet till Ringbergs (1991) regionala lervarvskronologi från sydöstra Sverige, göra pollenanalyser och glödförlustbestämningar har en del luckor i Hanöbuktens historia fyllts i.
I borrkärnorna finns fyra gemensamma enheter; en diamikton, enhet 1, två varviga enheter, enhet 2 och 4 samt ett organiskt lager, enhet 3 som skiljer de båda varviga enheterna åt.
Resultaten från analyserna samt jämförelser med liknande studier visar att de tre undre enheterna är avsatta under och efter Ristingeframstöten för ca 60 000 kal år sedan. Detta baseras bland annat på en tidigare datering av enhet 3, det organiska lagret, till mer än 38 000 kal år BP. De varviga lerorna tros vara avsatta under glaciala eller interstadiala förhållanden med iskanten relativt nära medan den organiska enheten snarare är avsatt distalt från iskanten i en omgivning med en del vegetation i form av örter och buskar. Enhet 4 korrelerades till Ringberg (1991)och daterades på så sätt till mellan 14 550 kal år BP och 14 750 kal år BP vilket placerar enheten under tidsperioden för interstadialen Bølling. På så vis konstaterades det att det saknas cirka 25 000 kal år mellan enhet 3 och 4. Denna hiatus kan till exempel bero på att den skandinaviska inlandsisen eroderat bort dessa avlagringar under tiden för
LGM alternativt att ingen avsättning har skett.
Slutligen kan det konstateras att förståelsen för Hanöbuktens yngre geologiska utveckling fortfarande inte är komplett men att dessa nya resultat åtminstone kan räta ut några av de tidigare frågetecknen. (Less)
Please use this url to cite or link to this publication:
author
Åberg, Gisela LU
supervisor
organization
alternative title
The stratigraphy in Hanö Bay during the last glaciation : a study of cores from IODP’s expedition no 347
course
GEOL01 20141
year
type
M2 - Bachelor Degree
subject
keywords
ice-rafted debris, lervarvskronologi, Bølling, IODP, Hanöbukten, Östersjön
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
393
language
Swedish
additional info
Extern handledare Thomas Andrén, Södertörns högskola
id
4459746
date added to LUP
2014-06-05 15:05:35
date last changed
2015-01-31 03:57:46
@misc{4459746,
  abstract     = {The development of Hanö Bay during the last ice age has been investigated by analyzing cores from IODP’s Balitc Sea Palaeoenvironment expedition in the Baltic Sea.
By analyzing the presence of Ice Rafted Debris, correlating one of the varved clay units to Ringbergs (1991)regional varve chronology from southeastern Sweden, analyzing pollen grains and measuring loss on ignition a few gaps in the history of Hanö Bay has been uncovered.
Four common units are found in the cores; a diamict unit, two varved clay units and an organic layer that separates the two varved clay units. The results from the analyzes, combined with the results from similar studies, show that the three lower units have been deposited after the Middle Weichselian Ristinge Ice Advance at approximately 60 ka BP. This is based partly on a former dating of unit 3, the organic layer, which showed an age of more than 38 ka. The varved clays are presumed to be deposited during glacial/interstadial conditions with a
proximal ice margin while the organic layer, unit 3, is supposed to have been deposited further away from the ice margin in an environment with some vegetation including herbs, grasses, shrubs and some trees. Unit 4 was correlated to Ringberg (1991) and was therefore dated to between 14 550 cal yr BP and 14 750 cal yr BP placing the unit during the Bølling interstadial. From this it was concluded that 25 ka is missing between units 3 and 4. This hiatus can be explained in different ways. It is, for example, possible that the Scandinavian ice sheet has eroded the unit during the Last Glacial Maximum, but there is also a possibility that no deposition took place during this time.
It was finally concluded that the younger geologic development of the Hanö Bay still is still not fully understood but that at least some of the earlier questions have been solved by these new results.},
  author       = {Åberg, Gisela},
  keyword      = {ice-rafted debris,lervarvskronologi,Bølling,IODP,Hanöbukten,Östersjön},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {Stratigrafin i Hanöbukten under senaste glaciationen : en studie av borrkärnor från IODP’s expedition nr 347},
  year         = {2014},
}