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Assessing the biodiversity crisis within the Triassic-Jurassic boundary interval using redox sensitive trace metals and stable carbon isotope geochemistry

Viðarsdóttir, Halla Margrét LU (2020) GEOR02 20192
Department of Geology
Abstract
Around the Triassic-Jurassic-Boundary time interval, a severe mass extinction event occurred, which has been associated to volcanism of the Central Atlantic Magmatic Province (CAMP). Significant amounts of greenhouse gases as carbon dioxide (CO2) or methane (CH4) and other volatiles are suggested to have been released into the atmosphere, leading to global warming with subsequent impact on the biosphere. The marine realm was affected to a greater extent than observed from the terrestrial record and there, the biotic recovery was slow and prolonged. The causes of this severe extinction and protracted recovery in the oceans are still not well understood. One recurring hypotheses is the presence of extended anoxic conditions in neritic... (More)
Around the Triassic-Jurassic-Boundary time interval, a severe mass extinction event occurred, which has been associated to volcanism of the Central Atlantic Magmatic Province (CAMP). Significant amounts of greenhouse gases as carbon dioxide (CO2) or methane (CH4) and other volatiles are suggested to have been released into the atmosphere, leading to global warming with subsequent impact on the biosphere. The marine realm was affected to a greater extent than observed from the terrestrial record and there, the biotic recovery was slow and prolonged. The causes of this severe extinction and protracted recovery in the oceans are still not well understood. One recurring hypotheses is the presence of extended anoxic conditions in neritic shallow seas.
The aim of this study was to address redox conditions of the European epicontinental sea during this time interval. Two cores from the Triassic-Jurassic boundary sedimentary successions were sampled with the target to gain further knowledge on the oxygen conditions that prevailed during time of deposition. One core comes from Stenlille, well nr. 4 from the Danish Basin (Denmark) and the other one, from Schandelah. Schandelah is located within the north German Lower Saxony Basin. Successions from both localities constitute shallow marine to coastal sandstones, mudstones and shales. Variations in oxygen grades of these successions was addressed with elemental analysis, evaluating enrichments of V, Mo, U, Zn, Cr, Co, Cu, Mn and their covariation with Al and TOC. The results indicate that anoxic conditions where generally not met in the seas at those localities during this time interval. Hg and Ni were used as markers of volcanic activities. In Stenlille, one level of anomalous concentrations of Hg and Ni is present, and in Schandelah two anomalous levels are present. At both localities, abnormal accumulation of both Hg and Ni coincide with a negative δ13Corg excursion associated to CAMP, which may indicate that the enrichment of these elements was due to volcanic activity. δ13Corg values are presented here for Stenlille 4, and serve as a tool for stratigraphic correlation between TJB successions. (Less)
Abstract (Swedish)
I övergången mellan de triassiska och jurassiska perioderna, för ca 200 miljoner år sedan, inträffade ett massutdöende som bedöms ha koppling till vulkanism i den Centralatlantiska magmatiska provinsen (CAMP). En signifikant ökning av växthusgaser som koldioxid (CO2) eller metan (CH4) och andra flyktiga ämnen, med efterföljande global uppvärmning som följd, föreslås vara den viktigaste drivkrafterna för påverkan på biosfären under detta tidsintervall. Den grundmarina miljön påverkades speciellt mycket och där var den biotiska återhämtningen långsam och långvarig. De direkta orsakerna till massutdöendet och den utdragna återhämtningen i haven är fortfarande inte väl förstådda. En hypotes är att syrefattiga eller syrefria miljöer uppstod i... (More)
I övergången mellan de triassiska och jurassiska perioderna, för ca 200 miljoner år sedan, inträffade ett massutdöende som bedöms ha koppling till vulkanism i den Centralatlantiska magmatiska provinsen (CAMP). En signifikant ökning av växthusgaser som koldioxid (CO2) eller metan (CH4) och andra flyktiga ämnen, med efterföljande global uppvärmning som följd, föreslås vara den viktigaste drivkrafterna för påverkan på biosfären under detta tidsintervall. Den grundmarina miljön påverkades speciellt mycket och där var den biotiska återhämtningen långsam och långvarig. De direkta orsakerna till massutdöendet och den utdragna återhämtningen i haven är fortfarande inte väl förstådda. En hypotes är att syrefattiga eller syrefria miljöer uppstod i grundhaven.

Syftet med denna studie är att undersöka detta ämne genom analys av samtida, idag fossila, sediment dokumentera redoxförhållandena i det europeiska grundhavet. Två borrkärnor med sedimentära bergarter från övergången mellan trias och jura undersöktes med målet för att få ytterligare kunskap om syreförhållandena som rådde under tiden för deposition. En kärna kommer från Stenlille, brunn nr. 4, från Danska bassängen (Danmark) och den andra från Schandelah i den nordtyska Niedersachsenbassängen. Bergarterna i Stenlille- och Schandelahkärnorna är sandsten, siltsten, skiffer och lersten som avlagrats i kust- eller grundmarina miljöer. För att utvärdera under vilka syreförhållanden som rådde i havet när sedimenten avsattes, analyserades koncentrationerna av V, Mo, U, Zn, Cr, Co, Cu och Mn samt deras förhållande till Al och halten organiskt kol (TOC). Resultaten indikerar att syrefria (anoxiska) förhållanden i allmänhet inte existerade och att miljön normalt var syresatt till svagt syresatt. Hg och Ni användes som markörer för vulkanisk aktivitet. Analys av dessa element påvisar en (1) nivå av avvikande ackumulering i Stenlillekärnan, och två i Schandelahkärnan. De höjda nivåerna av både Hg och Ni inträffar samtidigt som det sker negativa avvikelser i relationen mellan 12C och 13C (δ13Corg, dvs. i kolcykeln) i såväl Stenlillekärnan som Schandelahkärnan och korrelarar därför dessa händelser till utvecklingen i CAMP. Värden för δ13Corg presenteras här för Stenlille 4, och dessa fungerar som verktyg för stratigrafisk korrelation till andra områden och sedimentära successioner där den triassiska-jurassiska gränsen är känd. (Less)
Please use this url to cite or link to this publication:
author
Viðarsdóttir, Halla Margrét LU
supervisor
organization
alternative title
Utvärdering av den biologiska krisen runt det triassiska-jurassiska tidsintervallet genom analyser av redoxkänsliga spårmetaller och stabila kolisotoper
course
GEOR02 20192
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Stenlille, Schandelah, redox conditions, C-isotopes, marine sediments, trace elements, enrichment factors, mass extinction, Triassic – Jurassic boundary
report number
605
language
English
additional info
External supervisor: Sofie Lindström, GEUS
id
9026651
date added to LUP
2020-08-19 16:12:13
date last changed
2021-06-10 03:41:11
@misc{9026651,
  abstract     = {{Around the Triassic-Jurassic-Boundary time interval, a severe mass extinction event occurred, which has been associated to volcanism of the Central Atlantic Magmatic Province (CAMP). Significant amounts of greenhouse gases as carbon dioxide (CO2) or methane (CH4) and other volatiles are suggested to have been released into the atmosphere, leading to global warming with subsequent impact on the biosphere. The marine realm was affected to a greater extent than observed from the terrestrial record and there, the biotic recovery was slow and prolonged. The causes of this severe extinction and protracted recovery in the oceans are still not well understood. One recurring hypotheses is the presence of extended anoxic conditions in neritic shallow seas.
The aim of this study was to address redox conditions of the European epicontinental sea during this time interval. Two cores from the Triassic-Jurassic boundary sedimentary successions were sampled with the target to gain further knowledge on the oxygen conditions that prevailed during time of deposition. One core comes from Stenlille, well nr. 4 from the Danish Basin (Denmark) and the other one, from Schandelah. Schandelah is located within the north German Lower Saxony Basin. Successions from both localities constitute shallow marine to coastal sandstones, mudstones and shales. Variations in oxygen grades of these successions was addressed with elemental analysis, evaluating enrichments of V, Mo, U, Zn, Cr, Co, Cu, Mn and their covariation with Al and TOC. The results indicate that anoxic conditions where generally not met in the seas at those localities during this time interval. Hg and Ni were used as markers of volcanic activities. In Stenlille, one level of anomalous concentrations of Hg and Ni is present, and in Schandelah two anomalous levels are present. At both localities, abnormal accumulation of both Hg and Ni coincide with a negative δ13Corg excursion associated to CAMP, which may indicate that the enrichment of these elements was due to volcanic activity. δ13Corg values are presented here for Stenlille 4, and serve as a tool for stratigraphic correlation between TJB successions.}},
  author       = {{Viðarsdóttir, Halla Margrét}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Assessing the biodiversity crisis within the Triassic-Jurassic boundary interval using redox sensitive trace metals and stable carbon isotope geochemistry}},
  year         = {{2020}},
}