Structural investigation of ductile deformations across the Frontal Wedge south of Lake Vättern, southern Sweden
(2022) In Dissertations in Geology at Lund University GEOR02 20221Department of Geology
- Abstract (Swedish)
- Deformationszonen kallad ”Frontal wedge” är ett system av N-S branta och vertikala deformationszoner i gränsen mellan Svekonorvegiska och Sekorareliska provincen, i södra Sverige. Ursprung av dessa strukturer är inte fullt förstått och under de senaste årtiondena har endast ett fåtal undersökningar gjorts på dessa deformationszoner. Det finns flera olika tolkningar och modeller för bildandet av strukturerna i ”Frontal wedge”. Denna studie syftar att bidra med fältdokumentation av ett område söder om Vättern för att förbättra förståelsen för strukturerna och deras uppkomst. Den fältbaserade dokumentationen inkluderar strukturgeologiska mätningar av foliationsplan, tolkning av kinematiska indikatorer och petrografiska studier på bergarter... (More)
- Deformationszonen kallad ”Frontal wedge” är ett system av N-S branta och vertikala deformationszoner i gränsen mellan Svekonorvegiska och Sekorareliska provincen, i södra Sverige. Ursprung av dessa strukturer är inte fullt förstått och under de senaste årtiondena har endast ett fåtal undersökningar gjorts på dessa deformationszoner. Det finns flera olika tolkningar och modeller för bildandet av strukturerna i ”Frontal wedge”. Denna studie syftar att bidra med fältdokumentation av ett område söder om Vättern för att förbättra förståelsen för strukturerna och deras uppkomst. Den fältbaserade dokumentationen inkluderar strukturgeologiska mätningar av foliationsplan, tolkning av kinematiska indikatorer och petrografiska studier på bergarter tvärs över ”Frontal wedge”. Denna studie inkluderar även en jämförelse mellan strukturerna som studerats söder om Vättern och de norr om Vättern beskrivna av Wahlgren et al (1994). Resultaten påvisar att branta till vertikala deformationszoner tvärs över strykningen definierar en ”solfjäder”- eller ”wedge” struktur med konsekvent västra-blocket-upp kinematik. De petrografiska undersökningarna indikerar vidare att omkristallisation av fältspater och penetrativ deformation ökar från öst till väst i det studerade området. Den generella strukturen söder om Vättern liknar den som tidigare har beskrivits norrut. Den förespråkade modellen här, för utvecklingen av ”Frontal wedge” söder om Vättern, är att svaghetszoner bildade före Svekonorvegiska orogenesen är ursprunget för utvecklingen av ”Frontal wedge”. Dessa svaghetszoner reaktiverades under orogenesen och det påföljande upplyftandet av Östra Segmentet resulterade i bildandet av den branta deformationszonrema med västra-blocket-upp kinematik. Denna modell överensstämmer med den observerade strukturella geometrin, speciellt de dominerande branta till vertikala deformationsstrukturerna samt kinematiken härledd från kinematiska indikatorer och den gradvisa förändringen av deformationens karaktär i bergarterna från öst till väst i det studerade området. (Less)
- Abstract
- The Frontal wedge is a system of N-S trending steep to vertical deformation zones at the border between the Sveconorwegian and Svecokarelian provinces in south-central Sweden. The origin of these structures is not fully understood and few investigations have been done on these deformation zones during the past decades. There are various interpretations of and models for the formation of the structures within the Frontal wedge. This study seeks to add field documentation from an area south of Lake Vättern with the aim to improve the understanding of the structure and its development. The field-based documentation includes structural measurements of the gneissic foliations, interpretation of shear-sense indicators, and petrographic... (More)
- The Frontal wedge is a system of N-S trending steep to vertical deformation zones at the border between the Sveconorwegian and Svecokarelian provinces in south-central Sweden. The origin of these structures is not fully understood and few investigations have been done on these deformation zones during the past decades. There are various interpretations of and models for the formation of the structures within the Frontal wedge. This study seeks to add field documentation from an area south of Lake Vättern with the aim to improve the understanding of the structure and its development. The field-based documentation includes structural measurements of the gneissic foliations, interpretation of shear-sense indicators, and petrographic documentation of the rocks across the Frontal wedge. This study also includes a comparison between the structure south of Lake Vättern with the structure north of lake Vättern described by Wahlgren et al. (1994). The results show that steep to vertical westdipping deformation zones along an approximate E-W transect define a fan- or wedge-like structure with consistent western-blockup kinematics. Petrographic studies indicate that recrystallization of feldspar and penetrative deformation generally increases from east to west. The overall structural geometry in the studied area south of Lake Vättern resembles that described further north. The herein preferred model for the development of the Frontal wedge south of Vättern is that the structures originate from zones of weakness along intrusions formed before the Sveconorwegian orogeny. These zones were reactivated during the orogeny and the late-orogenic exhumation of the Eastern Segment and resulted in the formation of steep deformation zones with western-block-up kinematics. This model agrees with the observed structural geometry and especially the dominating vertical to near-vertical deformation zones. It is also in agreement with the kinematics derived from shear-sense indicators, and the gradational change in the character of the deformation of rocks from east to west in the study area south of lake Vättern. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9096104
- author
- Halvarsson, Ellinor LU
- supervisor
- organization
- course
- GEOR02 20221
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Frontal wedge, deformation zone, Sveconorwegian orogeny, Sveconorwegian Orogen, Eastern Segment, shear-sense indicators, Protogine zone, structural geology, bedrock geology
- publication/series
- Dissertations in Geology at Lund University
- report number
- 644
- language
- English
- id
- 9096104
- date added to LUP
- 2022-07-12 15:24:25
- date last changed
- 2022-07-12 15:24:25
@misc{9096104,
abstract = {{The Frontal wedge is a system of N-S trending steep to vertical deformation zones at the border between the Sveconorwegian and Svecokarelian provinces in south-central Sweden. The origin of these structures is not fully understood and few investigations have been done on these deformation zones during the past decades. There are various interpretations of and models for the formation of the structures within the Frontal wedge. This study seeks to add field documentation from an area south of Lake Vättern with the aim to improve the understanding of the structure and its development. The field-based documentation includes structural measurements of the gneissic foliations, interpretation of shear-sense indicators, and petrographic documentation of the rocks across the Frontal wedge. This study also includes a comparison between the structure south of Lake Vättern with the structure north of lake Vättern described by Wahlgren et al. (1994). The results show that steep to vertical westdipping deformation zones along an approximate E-W transect define a fan- or wedge-like structure with consistent western-blockup kinematics. Petrographic studies indicate that recrystallization of feldspar and penetrative deformation generally increases from east to west. The overall structural geometry in the studied area south of Lake Vättern resembles that described further north. The herein preferred model for the development of the Frontal wedge south of Vättern is that the structures originate from zones of weakness along intrusions formed before the Sveconorwegian orogeny. These zones were reactivated during the orogeny and the late-orogenic exhumation of the Eastern Segment and resulted in the formation of steep deformation zones with western-block-up kinematics. This model agrees with the observed structural geometry and especially the dominating vertical to near-vertical deformation zones. It is also in agreement with the kinematics derived from shear-sense indicators, and the gradational change in the character of the deformation of rocks from east to west in the study area south of lake Vättern.}},
author = {{Halvarsson, Ellinor}},
language = {{eng}},
note = {{Student Paper}},
series = {{Dissertations in Geology at Lund University}},
title = {{Structural investigation of ductile deformations across the Frontal Wedge south of Lake Vättern, southern Sweden}},
year = {{2022}},
}