Geoff Gilleaudeau

Geoff Gilleaudeau
George Mason University | GMU · Department of Atmospheric, Oceanic and Earth Sciences

Ph.D.

About

58
Publications
10,980
Reads
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754
Citations
Introduction
As a sedimentologist, stratigrapher, and geochemist, my work revolves around the chemical evolution of Earth's ocean-atmosphere system through geologic time. I am particularly interested in the co-evolution of life and environment during the Proterozoic Eon, as well linkages between between ocean oxygenation, biogeochemical cycles, and biotic turnover during the Paleozoic Era. I use a variety of sedimentological and geochemical tools applied to sedimentary rocks from across the globe.
Additional affiliations
March 2018 - July 2018
University of New Mexico
Position
  • Researcher
February 2016 - February 2018
Arizona State University
Position
  • PostDoc Position
February 2014 - January 2016
University of Copenhagen
Position
  • PostDoc Position
Education
August 2007 - June 2013
University of Tennessee
Field of study
  • Carbonate Sedimentology and Geochemistry, Proterozoic Ocean Oxygenation
August 2003 - May 2007
Binghamton University
Field of study
  • Experimental Metamorphic Petrology, Carbonate Sedimentology

Publications

Publications (58)
Article
Late Cretaceous to Early Paleogene time represents a critical transitional period in Earth history. Global events include short-term instability in climate and ocean circulation, large igneous province emplacement, and catastrophic extinction of marine and terrestrial fauna due at least in part to a bolide impact event. The response of the ocean sy...
Article
Full-text available
The terminal Ediacaran Period witnessed the decline of the Ediacara biota (which may have included many stem-group animals). To test whether oceanic anoxia might have played a role in this evolutionary event, we measured U isotope compositions (δ²³⁸U) in sedimentary carbonates from the Dengying Formation of South China to obtain new constraints on...
Article
Photic zone euxinia (PZE) is a condition where anoxic, H2S-rich waters occur in the photic zone (PZ). PZE has been invoked as an impediment to the evolution of complex life on early Earth and as a kill mechanism for Phanerozoic mass extinctions. Here, we investigate the potential application of mercury (Hg) stable isotopes in marine sedimentary roc...
Article
The middle Paleozoic (∼420-350 Myr) records a major increase in ocean-atmosphere oxygen levels; however, the timing and pattern of oxygenation are poorly constrained. Two well-dated North American locations in Nevada and Illinois were used to generate a high-resolution U-isotopic profile (δ 238 U) spanning ∼70 Myr of the middle Paleozoic. Stratigra...
Article
Uranium isotopes (δ²³⁸U values) in ancient sedimentary rocks (shales, carbonate rocks) are widely used as a tool to reconstruct paleo-redox conditions, but the behaviour of U isotopes under modern non-sulfidic anoxic vs. oxic conditions remains poorly constrained. We present U concentration and isotope data for modern sediments from the Peruvian ma...
Article
Full-text available
Geobiology explores how Earth's system has changed over the course of geologic history and how living organisms on this planet are impacted by or are indeed causing these changes. For decades, geologists, paleontologists, and geochemists have generated data to investigate these topics. Foundational efforts in sedimentary geochemistry utilized sprea...
Article
Redox state and salinity are fundamental properties of watermasses, and in modern environments, detailed analysis of spatial variability in redox and salinity is possible through direct measurement. Watermass reconstruction is difficult in deep-time systems, however, because the sedimentary record of ancient watermasses is often incomplete or diffi...
Article
Late Devonian marine systems were characterized by major environmental perturbations and associated biotic community changes linked to climate change and widespread oceanic anoxia. Here, we provide high-resolution lipid biomarker chemostratigraphic records from the Upper Devonian Chattanooga Shale (Tennessee, USA) to investigate algal-microbial com...
Article
The Ediacaran-Cambrian transition was characterized by the evolution from Ediacaran soft-body to Cambrian skeletal organisms, and fluctuations of the marine carbon cycle. Marine redox changes should have played an essential role in both ecological and environmental evolutions; however, temporary changes and spatial distribution of redox conditions...
Article
Fundamental questions persist regarding the redox structure and trace metal content of the Mesoproterozoic oceans. Multiple lines of evidence suggest more widespread anoxia in the deep oceans compared to today, and iron speciation indicates that anoxia was largely accompanied by dissolved ferrous iron (ferruginous conditions) rather than free sulfi...
Conference Paper
Full-text available
The terminal Ediacaran Period witnessed the first appearance of macroscopic organisms including the earliest biomineralizing animals in Earth history (Narbonne et al., 2012; Xiao et al., 2016). However, the biogeochemical context for this evolutionary milestone remains uncertain due to the absence of radiometric constraints for key events recorded...
Article
Recognition of stratigraphic hiatuses in fine-grained siliciclastic sedimentary rocks can be challenging but is feasible using high-resolution biostratigraphic and chemostratigraphic data within a regional correlation framework. In this case study of the Upper Devonian Chattanooga Shale in the Dupont GHS drillcore from the western margin of the Nas...
Conference Paper
The Early Mississippian (Tournaisian) positive δ13C excursion (or TICE) is one of the largest recorded in the Phanerozoic with magnitudes of change of up to +7‰. It is associated with a positive δ18O shift signaling global cooling and an increase in Southern Hemisphere continental glaciation. We are testing the hypothesis that increased ocean anoxi...
Article
Full-text available
The GHOST field tests are designed to isolate and test science-driven rover operations protocols, to determine best practices. During a recent field test at a potential Mars 2020 landing site analog, we tested two Mars Science Laboratory data-acquisition and decision-making methods to assess resulting science return and sample quality: a linear met...
Article
The Vindhyan Basin of north-central India contains a thick, areally extensive, largely unmetamorphosed succession of sedimentary rocks deposited during the Proterozoic Eon. Despite a wealth of studies aimed at using Vindhyan Basin strata as an archive for Proterozoic global events, fundamental questions persist about basic aspects of Vindhyan Basin...
Article
Chromium (Cr) stable isotopes are a useful tracer of changes in redox conditions because changes in its oxidation state are accompanied by an isotopic fractionation. Recent co-precipitation experiments have shown that Cr(VI) is incorporated into the calcite lattice, suggesting that carbonates are a potential sink for dissolved Cr in the ocean and c...
Conference Paper
Full-text available
A broad suite of redox proxy data suggest that despite ocean and atmosphere oxygenation in the late Neoproterozoic, euxinic conditions persisted in the global deep oceans until the at least Ordovician [1-3]. Major changes in the sulphur isotopic composition of carbonate associated sulphate and co-existing pyrite in the later Middle Ordovician are c...
Article
Full-text available
Oxygenation of Earth's oceans in the Proterozoic was a protracted process that began prior to the Great Oxidation Event (GOE) and culminated in deep ocean ventilation following Neoproterozoic glacial episodes, with both of these major thresholds accompanied by profound changes in the evolution of Earth's biosphere. Our understanding of the redox st...
Article
At present, a paucity of data from euxinic shales of the late Mesoproterozoic (1.3 to 1.0 Ga) limits our ability to relate marine redox evolution to biological innovation during a critical interval of eukaryotic development. Here we present data from marine shales of the 1.1 Ga Atar and El Mreiti groups, Mauritania, which were deposited during sea...
Article
Full-text available
Growing recognition of triple-chain silicates in nature has prompted experimental research into the conditions under which they can form and the extent of solid solution that is feasible for some key chemical substitutions. Experiments were done primarily in the range of 0.1–0.5 GPa and 200–850 °C for durations of 18–1,034 h. A wide range of bulk c...
Article
Inital observations reveal that an anomalous high-energy breccia in the Mesoproterozoic Atar Group, Mauitania, is a possible candidate for an ancient tsunamite, which may have been triggered by a marine impact event.
Poster
Travertine successions from the Pleistocene of Tivoli, Italy, are commonly composed of mm- to cm-thick layers of �shrub-like’ calcite interbedded with wavy, stromatolitic laminae. Each �shrub’ is composed of an intricately branched aggregate of crystals that radiate upwards from a basal surface. Shrub layers are traceable across tens of meters, and...

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