Quantitative analysis of color changes in organic walled microfossils

The color of organic-walled microfossils = palynomorphs (acritarchs, dinoflagellate cysts, pollen, spores) has long been used to assess the thermal maturity of sedimentary rocks, especially in the context of hydrocarbon source rock investigations. In general, the color of palynomorphs ranges from translucent yellow for immature to dark brown and finally black opaque for highly thermally mature sediments (ca 120⁰C and above).

There are many different schemes developed to characterize colors and the relationship with other thermal maturity indicators such for example vitrinite reflection and illite crystallinity is well established. Recent studies of the end-Permian and the end-Triassic mass extinction interval have reported a short-term transient increased abundance of darkened pollen and spores which cannot be explained as the result of increased regional thermal maturity. In fact, only a proportion of organic microfossils (up to 25% max) showed the darkening. Also, other thermal maturity parameters do not show any signs of local heating.

To date, a comprehensive study of the degree of darkening and a taxonomy analysis of the dark microfossil assemblages is missing. The selective darkening has been tentatively related to environmental stress (acidification, wildfires) during the mass extinction but the exact mechanism behind this singularity remains a mystery. The suggested project(s) is the first systematic and quantitative analysis of this darkening phenomenon during these periods of mass extinctions.

There are either several MSc research projects available focusing on the end-Permian or the end-Triassic mass extinction. The material for this study is present in the collection of the supervisor (W.M.Kürschner) but additional material may be collected during fieldwork for example in Austria or Italy (pending the situation of the Corona pandemic).

Methods:

  • Quantitative microscopic analysis of Permian-Triassic and/ or Triassic-Jurassic palynomorph assemblages with respect to the occurrence of color changes, the abundance, and the taxonomic distribution of darkened palynomorphs
  • Color index scoring using different techniques, analog and digital spectral analysis
  • Micro FTIR spectroscopic analysis of selected palynomorphs
  • Development of digital image analysis protocol to study digitally scanned microscopic slides and the use of image analysis with machine learning
Dark spore from the TJ mass extinction

 

Published May 3, 2021 5:00 PM - Last modified May 3, 2021 5:00 PM

Scope (credits)

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