Karaktärisering av laminerade marina sediment under ett globalt utdöende (silur, Gotland)
(2025) In Examensarbeten i geologi vid Lunds universitet GEOL02 20251Department of Geology
- Abstract (Swedish)
- Mulde Event, under mellansiluriska wenlock, utgör en period med globala störningar i ekologi och geokemi, bland annat ett drastiskt graptolitutdöende. I marina sediment från denna period har ett laminerat in-tervall identifierats i flera borrkärnor runt Östersjöområdet, inklusive Gotland, men intervallets ursprung och bety-delse är fortfarande inte klarlagt. I detta arbete analyseras lamineringen i borrkärnan Stora Sutarve-1 från södra Gotland, med hjälp av ljus- och polarisationsmikroskopi samt svepelektronmikroskopi (SEM) och energidispersiv röntgenspektroskopi (EDS/EDX). Syftet är att karaktärisera lamineringen och koppla den till möjliga sedimentära och marina miljöförändringar under Mulde Event, med hypotesen att havsmiljöförändringar... (More)
- Mulde Event, under mellansiluriska wenlock, utgör en period med globala störningar i ekologi och geokemi, bland annat ett drastiskt graptolitutdöende. I marina sediment från denna period har ett laminerat in-tervall identifierats i flera borrkärnor runt Östersjöområdet, inklusive Gotland, men intervallets ursprung och bety-delse är fortfarande inte klarlagt. I detta arbete analyseras lamineringen i borrkärnan Stora Sutarve-1 från södra Gotland, med hjälp av ljus- och polarisationsmikroskopi samt svepelektronmikroskopi (SEM) och energidispersiv röntgenspektroskopi (EDS/EDX). Syftet är att karaktärisera lamineringen och koppla den till möjliga sedimentära och marina miljöförändringar under Mulde Event, med hypotesen att havsmiljöförändringar är orsaken. Lamine-ringen består av 52 växelvisa mörka och ljusa lager utan tecken på bioturbation, vilket indikerar syrefattiga förhål-landen. De två mikrofacies skiljer sig i mineralogi och struktur; ljusa lager består främst av mikrit, medan de mörka främst innehåller illitiska lermineral och organiskt material. Framboidal pyrit förekommer genomgående i de mörka lagren vilket visar på reducerande miljöer, medan förekomst av baryt antyder kortvariga syrerika episoder. Lamine-ringen tolkas som ett resultat av sedimentation i en djup, periodvis anoxisk miljö, orsakad av instabila marina för-hållanden under Mulde Event. Variationer i redoxförhållanden tyder på ett dynamiskt havssystem, där miljösväng-ningar, möjligen kopplade till säsongsvariationer, styrt faciesutvecklingen. Studien stödjer hypotesen att havsmiljö-förändringar låg bakom lamineringens bildning. För att förstå lamineringens regionala spridning och depositions-miljö bättre rekommenderas vidare arbete med stratigrafisk korrelation och detaljerad geokemisk profilering. (Less)
- Abstract
- The Mulde Event, during the mid-Silurian Wenlock epoch, represents a period of global ecological and geochemical disturbances, including a drastic extinction of graptolites. Within marine sediments from this interval, a laminated sequence has been identified in several drill cores across the Baltic region, including Gotland; however, the origin and significance of this sequence remain poorly understood. In this study, an interval in the laminated section, in the drill core Stora Sutarve-1 from southern Gotland, is examined using light and polarized microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS/EDX) The aim is to cha-racterize the lamination and relate it to potential sedimentary and marine... (More)
- The Mulde Event, during the mid-Silurian Wenlock epoch, represents a period of global ecological and geochemical disturbances, including a drastic extinction of graptolites. Within marine sediments from this interval, a laminated sequence has been identified in several drill cores across the Baltic region, including Gotland; however, the origin and significance of this sequence remain poorly understood. In this study, an interval in the laminated section, in the drill core Stora Sutarve-1 from southern Gotland, is examined using light and polarized microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS/EDX) The aim is to cha-racterize the lamination and relate it to potential sedimentary and marine environmental changes during the Mulde Event, under the hypothesis that changes in marine conditions were the primary driver. The studied interval consists of 52 alternating dark and light layers with no evidence of bioturbation, suggesting deposition under oxygen-deficient conditions. The two microfacies differ in mineralogy and texture; the light layers are predominantly com-posed of micrite, while the dark layers contain mostly illitic clay minerals and organic matter. Framboidal pyrite is consistently present in the dark layers, indicating reducing conditions, whereas the occurrence of barite suggests brief oxic episodes. The lamination is interpreted as the result of sedimentation in a deep, low-energy, and intermit-tently anoxic environment, driven by unstable marine conditions during the Mulde Event. Variations in redox con-ditions point to a dynamic marine system where environmental fluctuations, possibly related to seasonal variations, controlled facies development. This study supports the hypothesis that the formation of the laminated interval was caused by changes in marine conditions. To better understand the regional extent and depositional setting of the lamination, further work involving detailed stratigraphic correlation and geochemical profiling is recommended. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9199424
- author
- Zellman, Oskar LU
- supervisor
- organization
- course
- GEOL02 20251
- year
- 2025
- type
- M2 - Bachelor Degree
- subject
- keywords
- laminerade sediment, Gotland, Mulde Event, silur, wenlock.
- publication/series
- Examensarbeten i geologi vid Lunds universitet
- report number
- 707
- language
- Swedish
- id
- 9199424
- date added to LUP
- 2025-06-16 09:29:58
- date last changed
- 2025-06-16 09:29:58
@misc{9199424,
abstract = {{The Mulde Event, during the mid-Silurian Wenlock epoch, represents a period of global ecological and geochemical disturbances, including a drastic extinction of graptolites. Within marine sediments from this interval, a laminated sequence has been identified in several drill cores across the Baltic region, including Gotland; however, the origin and significance of this sequence remain poorly understood. In this study, an interval in the laminated section, in the drill core Stora Sutarve-1 from southern Gotland, is examined using light and polarized microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS/EDX) The aim is to cha-racterize the lamination and relate it to potential sedimentary and marine environmental changes during the Mulde Event, under the hypothesis that changes in marine conditions were the primary driver. The studied interval consists of 52 alternating dark and light layers with no evidence of bioturbation, suggesting deposition under oxygen-deficient conditions. The two microfacies differ in mineralogy and texture; the light layers are predominantly com-posed of micrite, while the dark layers contain mostly illitic clay minerals and organic matter. Framboidal pyrite is consistently present in the dark layers, indicating reducing conditions, whereas the occurrence of barite suggests brief oxic episodes. The lamination is interpreted as the result of sedimentation in a deep, low-energy, and intermit-tently anoxic environment, driven by unstable marine conditions during the Mulde Event. Variations in redox con-ditions point to a dynamic marine system where environmental fluctuations, possibly related to seasonal variations, controlled facies development. This study supports the hypothesis that the formation of the laminated interval was caused by changes in marine conditions. To better understand the regional extent and depositional setting of the lamination, further work involving detailed stratigraphic correlation and geochemical profiling is recommended.}},
author = {{Zellman, Oskar}},
language = {{swe}},
note = {{Student Paper}},
series = {{Examensarbeten i geologi vid Lunds universitet}},
title = {{Karaktärisering av laminerade marina sediment under ett globalt utdöende (silur, Gotland)}},
year = {{2025}},
}