Advanced

A sedimentological study of glacial deposits in the upper Sjællandselv area, Jameson Land, East Greenland

Andersson, Torbjörn (1994) In Dissertations in Geology at Lund University
Department of Geology
Abstract
Summary: The fieldwork preceding this Master degree thesis took place in Jameson Land, East Greeniand, within the frame of the PONAM (Polar North Atlantic Margins; Late Cenozoic evolution) project.
In central Jameson Land, a plateau area at approximately 500 m.a.s.l. forms a marked height in the area around the uppermost reaches of Jyllandselv. Ac. 2 km wide valley, where river ravines are cut down more than 100 m into the Jurassic bedrock, divides the plateau into a northern and a southern part. The investigated area is located in the southern part of the plateau area, between the two deep river valleys of upper Sjællandselv and upper Jyllandselv, where two elongated hills with top surfaces at approximately 510 m.a.s.l. form a 5 km long... (More)
Summary: The fieldwork preceding this Master degree thesis took place in Jameson Land, East Greeniand, within the frame of the PONAM (Polar North Atlantic Margins; Late Cenozoic evolution) project.
In central Jameson Land, a plateau area at approximately 500 m.a.s.l. forms a marked height in the area around the uppermost reaches of Jyllandselv. Ac. 2 km wide valley, where river ravines are cut down more than 100 m into the Jurassic bedrock, divides the plateau into a northern and a southern part. The investigated area is located in the southern part of the plateau area, between the two deep river valleys of upper Sjællandselv and upper Jyllandselv, where two elongated hills with top surfaces at approximately 510 m.a.s.l. form a 5 km long till covered complex. The eastern hill has gentle slopes, whereas the western hill has terraced slopes on the northern, eastern and southern sides. Seven sites have been investigated through detailed sedimentological logging of excavated sections and four lithostratigraphic units, A-D, have been distinguished.
Unit A shows fine sand and coarse silt sediments dominated by type A and type B ripple cross-lamination and planar parallel-lamination. These sediments are interpreted to be formed by rapid deposition from turbidity currents along a prodelta slope or at the distal parts of a subaqueous fan. Palaeocurrents show a dispersed pattern towards the south, south-east, east, north-east and the north.
Unit B consists of a diamicton with a coarse to medium sand matrix and boulders up to 1 m in diameter occur. The diamicton is interpreted to be a till. It covers the two elongated hills and lies on top of unit A. A fabric analysis shows an ice-movement towards the south-east.
Unit C comprises sandy fluvial bedforms. Trough cross-lamination formed by the migration of 3-D dunes is the most common lithofacies and is interpreted as in channel deposition of a sandy braided river. Palaeocurrents are opposed to the present drainage system.
Unit D is a diamicton with a high silt and clay content in the matrix. It can be found on top of the fluvial terraces. The diamicton is interpreted to be a till. At one of the sites this till is intensely deformed and folded and interpreted as a B-horizon in a subglacial deformation zone. The strike of fold axes show a direction of stress approximately towards the south-west.
The sediment successions reveal the former existence of a glacial lake in front of a damming glacier in the west. Since the palaeocurrents are approximately opposed to the present drainage system, the glacier margin is assumed to have been located relatively near. The absence of coarsegrained upper delta slope sediments as well as topset sediments of an ice-contact delta indicates that the sediments of unit A are prodelta or distal subaqueous fan deposits. Unit B represents the deposition of an advancing glacier from the west, that most likely was the same glacier that dammed the glacial lake. During deglaciation, proglacial meltwater erosion and fluvial terrace sediment deposition took place as revealed by unit C sediments. Palaeocurrents that are approximately opposed to the present drainage system, indicate that the glacier still existed in the west. The last recorded event in the area is a new glacial advance from the north-east. This is shown by the deformation till of unit D. (Less)
Please use this url to cite or link to this publication:
author
Andersson, Torbjörn
supervisor
organization
year
type
H1 - Master's Degree (One Year)
subject
keywords
geography, geology, sedimentology, glacial deposit, Sjællandselv area, Jameson Land, Greenland
publication/series
Dissertations in Geology at Lund University
report number
57
funder
European Science Foundation
language
English
id
2370090
date added to LUP
2012-08-14 12:22:05
date last changed
2012-08-14 12:22:05
@misc{2370090,
  abstract     = {Summary: The fieldwork preceding this Master degree thesis took place in Jameson Land, East Greeniand, within the frame of the PONAM (Polar North Atlantic Margins; Late Cenozoic evolution) project.
In central Jameson Land, a plateau area at approximately 500 m.a.s.l. forms a marked height in the area around the uppermost reaches of Jyllandselv. Ac. 2 km wide valley, where river ravines are cut down more than 100 m into the Jurassic bedrock, divides the plateau into a northern and a southern part. The investigated area is located in the southern part of the plateau area, between the two deep river valleys of upper Sjællandselv and upper Jyllandselv, where two elongated hills with top surfaces at approximately 510 m.a.s.l. form a 5 km long till covered complex. The eastern hill has gentle slopes, whereas the western hill has terraced slopes on the northern, eastern and southern sides. Seven sites have been investigated through detailed sedimentological logging of excavated sections and four lithostratigraphic units, A-D, have been distinguished.
Unit A shows fine sand and coarse silt sediments dominated by type A and type B ripple cross-lamination and planar parallel-lamination. These sediments are interpreted to be formed by rapid deposition from turbidity currents along a prodelta slope or at the distal parts of a subaqueous fan. Palaeocurrents show a dispersed pattern towards the south, south-east, east, north-east and the north.
Unit B consists of a diamicton with a coarse to medium sand matrix and boulders up to 1 m in diameter occur. The diamicton is interpreted to be a till. It covers the two elongated hills and lies on top of unit A. A fabric analysis shows an ice-movement towards the south-east.
Unit C comprises sandy fluvial bedforms. Trough cross-lamination formed by the migration of 3-D dunes is the most common lithofacies and is interpreted as in channel deposition of a sandy braided river. Palaeocurrents are opposed to the present drainage system.
Unit D is a diamicton with a high silt and clay content in the matrix. It can be found on top of the fluvial terraces. The diamicton is interpreted to be a till. At one of the sites this till is intensely deformed and folded and interpreted as a B-horizon in a subglacial deformation zone. The strike of fold axes show a direction of stress approximately towards the south-west.
The sediment successions reveal the former existence of a glacial lake in front of a damming glacier in the west. Since the palaeocurrents are approximately opposed to the present drainage system, the glacier margin is assumed to have been located relatively near. The absence of coarsegrained upper delta slope sediments as well as topset sediments of an ice-contact delta indicates that the sediments of unit A are prodelta or distal subaqueous fan deposits. Unit B represents the deposition of an advancing glacier from the west, that most likely was the same glacier that dammed the glacial lake. During deglaciation, proglacial meltwater erosion and fluvial terrace sediment deposition took place as revealed by unit C sediments. Palaeocurrents that are approximately opposed to the present drainage system, indicate that the glacier still existed in the west. The last recorded event in the area is a new glacial advance from the north-east. This is shown by the deformation till of unit D.},
  author       = {Andersson, Torbjörn},
  keyword      = {geography,geology,sedimentology,glacial deposit,Sjællandselv area,Jameson Land,Greenland},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {A sedimentological study of glacial deposits in the upper Sjællandselv area, Jameson Land, East Greenland},
  year         = {1994},
}