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Dr William Defliese

Lecturer - Geochemistry

School of the Environment
Faculty of Science
w.defliese@uq.edu.au
+61 7 336 52176

Overview

I am a sedimentary geochemist, and I work on a variety of problems in sedimentary geology, paleoclimate, and basin analysis through the use of stable isotope geochemistry. My specialty is carbonate clumped isotope thermometry, though I use a variety of techniques in my work. Several areas of active research are outlined below.

Clumped Isotope Reordering and Basin Analysis

Currently I am investigating clumped isotope reordering - the change that occurs in a sample's clumped isotope value as a result of solid-state diffusion of 18O and/or 13C within the crystal lattice of a carbonate mineral. This is important to understand for two reasons. First, if we are trying to get accurate paleoclimate data using clumped isotope paleothermometry, we need to know what conditions (burial depth and heating) allow for primary signals, and under which conditions the primary signal is lost. Second, if we know the kinetics of clumped isotope reordering, we can then apply that knowledge to understand past heat flow in a basin. Combined with a stratigraphic column and burial history for a body of rock, we can reconstruct geothermal gradients, and evaluate tectonic/basin models based on whether they could produce the required heat flux to match observed clumped isotope values.

For this project, I am conducting heating experiments on a variety of carbonate minerals to define their reordering kinetics. As different minerals have different kinetics, some minerals appear to be more resistant to reordering (good for paleoclimate!), while others reorder faster and at lower temperatures (bad for paleoclimate!). When multiple mineralogies are present, a detailed burial heating model may be constructed incorporating information from each carbonate mineralogy. As a pilot study, we have applied this technique to core materials in the Permian Basin of West Texas. Results show that paired calcite-dolomite clumped isotopes yield reconstructed geothermal gradients similar to vitrinite reflectance, with the benefit that they can be applied to any carbonate present in the core.

Carbonate Sedimentation and Diagenesis

Carbonate sedimentation and diagenesis is one of my active research areas, with a focus on understanding how and if clumped isotopes recorded accurate temperatures in diagenetic environments. A large portion of this work has been in Bermuda, but I've been involved in several other projects where I have applied clumped isotopes to sedimentological problems. Clumped isotopes are useful here as it turns out they do record the temperature of formation in most cases, and can be applied to a variety of problems, such as contemporary dolomite formation, or the temperature of formation of otherwise engimatic carbonate textures, such as 'beef' calcites.

Paleoclimate Research

I have been interested in paleoclimate since I took my first geology class at Northwestern. Since then, I've worked on a variety of timescales and systems, but the common theme has been the application of clumped isotopes. Clumped isotopes are a wonderful tool for paleoclimate research in situations where the water oxygen isotope composition is uncertain, such as terrestrial and lacustrine settings, deep time where even the oxygen isotopic composition of the ocean is uncertain, or even in (relatively) more modern systems that might be affected by runoff or glacial meltwater. For example, samples I originally collected in Bermuda for a study on diagenesis eventually led to a paleoclimate study, where it was discovered that meltwater from the last glacial maximum may have temporarily but severely affect ocean circulation and temperature as far south as Bermuda (Winkelstern et al., 2017). I've also long been fascinated by the Neoproterozoic, as this was a highly dynamic time in Earth history, featuring the snowball earth glaciations, massive carbon isotope excursions, and the appearance of the first metazoans (possibly linked?), and am interested in developing research in this area.

Degrees and Positions Held

2008 B.A. Geological Sciences and Integrated Sciences (Honors), Northwestern University, Evanston, Illinois, USA

2014 Ph.D. Geology, University of Michigan, Ann Arbor, Michigan, USA

2014-2017 Postdoctoral Researcher, University of California, Los Angeles, California, USA

2017-2019 Berg-Hughes Postdoctoral Fellow, Texas A&M University, College Station, Texas, USA

2019-Present Lecturer in Geochemistry, University of Queensland

Research Interests

  • Stable Isotope Geochemistry
  • Sedimentary Geology
  • Paleoclimate
  • Carbonate Geochemistry

Qualifications

  • Doctor of Philosophy, University of Michigan

Publications

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Grants

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Supervision

  • Indian summer monsoon variability during the past ten thousand years

    Doctor Philosophy

  • Diffusion rates of 13C-18O clumping in dolomite and high Mg/Mn calcite

    Doctor Philosophy

  • Recycling halogens and noble gases in sediments and meta-sediments

    Doctor Philosophy

View all Supervision

Publications

Journal Article

Conference Publication

Grants (Administered at UQ)

PhD and MPhil Supervision

Current Supervision

  • Indian summer monsoon variability during the past ten thousand years

    Doctor Philosophy — Principal Advisor

  • Diffusion rates of 13C-18O clumping in dolomite and high Mg/Mn calcite

    Doctor Philosophy — Principal Advisor

    Other advisors:

  • Recycling halogens and noble gases in sediments and meta-sediments

    Doctor Philosophy — Associate Advisor

    Other advisors:

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Links

ORCID: 0000-0002-7730-4964

Scopus ID: 56512273700

Google Scholar ID: NxTXbl0AAAAJ

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