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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Sedimentary Factories and Ecosystem Change in the Triassic-Jurassic Boundary Interval : Insights from the Skåne Area (Southern Sweden) / Mikrobiella sedimentbildningar och ekosystemsförändring vid Trias-Juragränsen : Insikter från Skåne

Nesset Mattsson, Gustav January 2021 (has links)
The End-Triassic Extinction (ETE) has long remained one of the lesser known among the so-called “Big Five”. There exist several hypotheses regarding the probable cause of this extinction, which can mainly be divided into  events of  a decline in the rate of diversification  in the late Triassic contra a sudden and significant extinction event. Primary amongst the sudden events is the one of outgassing and climate/environmental change induced by Central Atlantic Magmatic Province (CAMP) volcanism. This  study  aims to  describe  the ETE using  fluvial, lacustrine, deltaic  and  marginal-marine  microbial sedimentary  structures (MS), carbonatized microbial mats (CMM) as well as  wrinkle structures, microbially  induced  sedimentary  structures (MISS) from the latest  Triassic-  earliest  Jurassic  (TJB: Triassic-Jurassic boundary interval, Rhaetian to Hettangian) of Skåne, Southern Sweden. The MISS in these sites show a high diversity of structures, indicating microbial communities with high diversity in an environment usually dominated by bioturbating invertebrates. We observed structures that include top-surface (“Elephant skin”) and subsurface (“Kinneyia”) structures, carbon-rich fossilized microbial mats, microbial sideritic concretions, sideritized microbial mats, stromatolite-like layers and oncoids. Scanning Electron Microscopy (SEM) sampling also revealed structures related to the presence of both coccoidal and filamentous cyanobacteria.  Overall,  the diversity in observed structures indicate a thriving microbial community, with diversified and abundant ichnofossils or body fossils of possible bioturbators only observed in the early Rhaetian and younger Mid-Late Hettangian samples of deltaic or marginal-marine affinities. The lack of metazoan communities to such an extent indicates that the local environment could have reversed to a pre-Substrate Revolution state. The occurrence of abundant and  diversified  microbial structures in the studied  TJB  section,  representing  a relatively  short time interval, reflects anachronistic facies and development of abnormal biota. This supports the occurrence of several environmental distresses (abnormal hydrochemical and physical conditions) on the Triassic-Jurassic boundary interval, in turn lending credence to the hypothesis of an abrupt climactic event such as possibly that of CAMP volcanism. / <p>Presentation was carried out online over zoom due to the at the time ongoing COVID-19 pandemic.</p> / Resurrecting a lost world in Skåne: new light on the end-Triassic mass extinction and the origin of the dinosaur dominated ecosystem / Dinosaur grave from Skåne: microbiology, taphonomy and paleomolecules of exceptionally preserved theropod remains

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