Advanced

Sedimentologisk undersökning av en moränskärning i en djupvittrad sprickdal på Romeleåsen, Skåne

Gunnarson, Rebecka (2001) In Examensarbeten i geologi vid Lunds universitet
Department of Geology
Abstract (Swedish)
Populärvetenskaplig sammanfattning: Dagens landskap bär på många spår från den senaste istiden. Det kan röra sig om räfflor på berghällar som bildats när inlandsisen med sten och grus glidit fram över en berggrundsyta, eller olika lager av lösa jordarter som transporterats och avlagrats av inlandsisen. Geologer använder dessa spår när de försöker rekonstruera nedisningsförloppet. Genom detaljstudier av de lösa jordlagren kan man dra slutsatser om vilka avlagringsprocesser som varit verksamma och vilka avlagringsmiljöer som existerat. Med undersökningar från olika platser i en större region är det möjligt att rekonstruera inlandsisens dynamik och utveckling i ett vidare sammanhang.

Min undersökning i Bellinga stenbrott på Romeleåsen... (More)
Populärvetenskaplig sammanfattning: Dagens landskap bär på många spår från den senaste istiden. Det kan röra sig om räfflor på berghällar som bildats när inlandsisen med sten och grus glidit fram över en berggrundsyta, eller olika lager av lösa jordarter som transporterats och avlagrats av inlandsisen. Geologer använder dessa spår när de försöker rekonstruera nedisningsförloppet. Genom detaljstudier av de lösa jordlagren kan man dra slutsatser om vilka avlagringsprocesser som varit verksamma och vilka avlagringsmiljöer som existerat. Med undersökningar från olika platser i en större region är det möjligt att rekonstruera inlandsisens dynamik och utveckling i ett vidare sammanhang.

Min undersökning i Bellinga stenbrott på Romeleåsen berör en märklig moränfylld sprickdal. Berggrunden i området är mycket uppsprucken och djupvittrad. Moränen är avlagrad direkt på den söndervittrade bergytan, medan de vertikala bergväggarna nere i sprickdalen har spår av slipade ytor. Morän, som bildas under inlandsisen ligger vanligtvis på avslipade, fasta hällytor och syftet med min undersökning var att försöka förklara hur bergets söndervittrade överyta kunnat bevaras, trots att inlandsisen rört sig över platsen. Jag skulle också förklara varför slipningen bara skett djupt nere i sprickdalen.

Avlagringarna i sprickdalen består av ett undre och ett övre moränlager, som skiljs åt av ett tjockt lager med grusig sand. Moränernas utseende och egenskaper har jämförts med olika typer av morän, som finns beskrivna i den vetenskapliga litteraturen. (Less)
Abstract
A narrow gorge in deep weathered bedrock has been uncovered during quarrying at Romeleåsen horst, Skåne, southern Sweden. The gorge was filled up with a homogeneous diamicton deposited directly on the weathered surfaces, but also on vertical walls of glacially abraded bedrock. The filling sediments and the contact to the bedrock were investigated in purpose to interpret sedimentary processes and depositional environment. A till section was studied in detail, by doing lithofacies classification, fabric analyses, measurements of direction of deformation structures, and by sampling for analysis of grain size and clast lithology composition. The genesis of the diamicton was interpreted by comparing the sedimentary characteristics with known... (More)
A narrow gorge in deep weathered bedrock has been uncovered during quarrying at Romeleåsen horst, Skåne, southern Sweden. The gorge was filled up with a homogeneous diamicton deposited directly on the weathered surfaces, but also on vertical walls of glacially abraded bedrock. The filling sediments and the contact to the bedrock were investigated in purpose to interpret sedimentary processes and depositional environment. A till section was studied in detail, by doing lithofacies classification, fabric analyses, measurements of direction of deformation structures, and by sampling for analysis of grain size and clast lithology composition. The genesis of the diamicton was interpreted by comparing the sedimentary characteristics with known criteria of lodgement till and deformation till.

The sedimentary succession consists of a lower homogeneous, massive diamicton and an upper more heterogeneous diamicton. Layers of gravelly sand and breccia of local bedrock with a matrix of laminated silt to fine sand separate the two diamicton units.

The results suggest an interpretation of the diamictons as deformation till. The lower homogeneous diamicton was transported into the gorge by squeezing. As a result of the viscous sediment flow through the gorge, some parts of the walls became abraded. The gravelly sand represents fluvial sedimentation in a subglacial cavity, and the brecciated bedrock was sheared into the cavity. The upper heterogeneous diamicton was deposited as subglacial deformation till after the cavity was closed.

The changes in sedimentary environment suggest continuous subglacial conditions with high subglacial water-pressure and occasional bed separation during one single glacier advance. Clast fabric data and deformation structures indicate a glacier movement from SSW-SW, and the sedimentary sequence is related to the last ice advance of the late Weichselian glaciation in the area. (Less)
Please use this url to cite or link to this publication:
author
Gunnarson, Rebecka
supervisor
organization
alternative title
A sedimentological investigation of a till section in a gorge formed in deep weathered bedrock at Romeleåsen, south Sweden
year
type
H1 - Master's Degree (One Year)
subject
keywords
deformation till, glacial abrasion, late Weichselian glaciation, subglacial cavity sedimentation, subglacial environment, squeezed till
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
137
language
Swedish
id
2343900
date added to LUP
2012-11-06 12:58:50
date last changed
2012-11-06 12:58:50
@misc{2343900,
  abstract     = {A narrow gorge in deep weathered bedrock has been uncovered during quarrying at Romeleåsen horst, Skåne, southern Sweden. The gorge was filled up with a homogeneous diamicton deposited directly on the weathered surfaces, but also on vertical walls of glacially abraded bedrock. The filling sediments and the contact to the bedrock were investigated in purpose to interpret sedimentary processes and depositional environment. A till section was studied in detail, by doing lithofacies classification, fabric analyses, measurements of direction of deformation structures, and by sampling for analysis of grain size and clast lithology composition. The genesis of the diamicton was interpreted by comparing the sedimentary characteristics with known criteria of lodgement till and deformation till.

The sedimentary succession consists of a lower homogeneous, massive diamicton and an upper more heterogeneous diamicton. Layers of gravelly sand and breccia of local bedrock with a matrix of laminated silt to fine sand separate the two diamicton units.

The results suggest an interpretation of the diamictons as deformation till. The lower homogeneous diamicton was transported into the gorge by squeezing. As a result of the viscous sediment flow through the gorge, some parts of the walls became abraded. The gravelly sand represents fluvial sedimentation in a subglacial cavity, and the brecciated bedrock was sheared into the cavity. The upper heterogeneous diamicton was deposited as subglacial deformation till after the cavity was closed.

The changes in sedimentary environment suggest continuous subglacial conditions with high subglacial water-pressure and occasional bed separation during one single glacier advance. Clast fabric data and deformation structures indicate a glacier movement from SSW-SW, and the sedimentary sequence is related to the last ice advance of the late Weichselian glaciation in the area.},
  author       = {Gunnarson, Rebecka},
  keyword      = {deformation till,glacial abrasion,late Weichselian glaciation,subglacial cavity sedimentation,subglacial environment,squeezed till},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {Sedimentologisk undersökning av en moränskärning i en djupvittrad sprickdal på Romeleåsen, Skåne},
  year         = {2001},
}