Special Guest Seminar - winter-2025
Fundamental Understanding of Physicochemical Properties of Minerals in Geological Processes Using Various Quantitative Tools
Feb. 5, 2025
1:30 p.m. - 2:30 p.m.
Geology 3814
Presented By:
- Prof. YoungJae Kim - Pukyong National University
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Understanding the structural, physical, and chemical properties of minerals occurring in geological systems is often complicated due to multiple components, phases, and variables involved in the systems. Recently, fundamental investigations on these subjects have been made possible by the refinement and widespread use of spectroscopic and microscopic techniques as well as fast development in computational methods. In this presentation, I demonstrate the application of quantum-mechanical modeling approaches for understanding thermodynamic properties of solid solution in minerals as well as the use of synchrotron X-ray approaches to elucidate structural and morphological relationships between multiple phases upon mineral replacement reactions. In various geological systems, minerals rarely occur as a pure end member but form solid solution to a certain degree or contain trace amounts of foreign ions in their structures. There have been numerous field and experimental studies investigating ionic substitution in minerals, while quantifying their thermodynamics and mechanisms are often difficult to empirically obtain. My research explores ionic substitution in the mineral structure in atomistic scales mainly based on density functional theory (DFT) calculation. Combined with statistical thermodynamic analysis, DFT modeling can be very useful to investigate complex solid solution systems (e.g., involving multiple atomic sites) allowing for predicting energetic stabilities of minerals in hydrothermal and magmatic systems. The mineral replacement is a coupled dissolution-growth process in which a primary mineral dissolves in contact with fluid and is replaced by a more stable secondary mineral. Understanding mineral replacement reactions is essential in many natural and industrial processes including metasomatism, diagenesis, and metamorphism, and nuclear waste disposal. My research pursues mechanistic understanding of mineral replacements based on synchrotron nanoscale X-ray imaging. Combined experimental and analytical approaches have been developed to understand how mineral replacement is modified by the crystallography of the primary and secondary mineral.
Hydrothermal alteration of organic molecules complicates our ability to reliably interpret life on Earth and potentially elsewhere
March 5, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Dr. Bonnie Teece - JPL
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Hydrothermal systems are areas where heated and chemically distinct vent fluid is discharged from the subsurface into varied environments. These systems have been reported in the ocean and on land and can be fuelled by magmatic activity, exothermic chemical reactions, or impact events. Hydrothermal systems are key target areas for geobiology and astrobiology because the steep gradients between hydrothermal fluid and the surrounding environment can rapidly precipitate minerals and release energy that can drive abiotic and prebiotic organic chemistry and support biological communities. In addition, most of the generally accepted evidence for early life on Earth is associated with hydrothermal environments (e.g., 3.5 Ga Dresser Formation, Western Australia; 3.5 Ga Middle Marker Horizon, Barberton, South Africa), and hydrothermal environments have been discovered on Mars, Enceladus and possibly Europa. However, organic biosignatures (fossilized lipids) are altered by heat and commonly undergo rapid advanced diagenesis from hydrothermal fluid, making assessing their origin difficult. Additionally, organic molecules can be transported from the subsurface and surrounding environments and cycled in the system, undergoing rapid temperature changes that further affect the robustness of biogenicity interpretations. Here, I will present my work in land-based and deep-sea hydrothermal systems across the geological record on Earth to determine how we can find the most pristine organic biosignatures possible and inform our search for life on other planetary bodies. My work has focused on contextually bound interpretations, as I have discovered that the migration and preservation of organic molecules are heavily affected by the porosity and crystallinity of the minerals, the minerals present, and the sample’s location within the hydrothermal field. Lastly, organic geochemical proxies are based on petroleum geochemistry, which assumes slow burial and subsidence instead of the flash heating that can occur during abrupt changes in (or the introduction of) hydrothermal fluids. This non-typical alteration is particularly important when we consider the application of Earth-biased studies to other planetary bodies which lack plate tectonics. I will discuss these imitations and outline areas for future research to improve organic biosignature interpretations in hydrothermal systems.
Insights into the coevolution of early life and planets from silica-hosted biosignatures
March 11, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Kelsey R. Moore - Johns Hopkins University
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Since the dawn of life on Earth, microbial organisms have played a central role in shaping our planet. If life ever arose on other planetary bodies like Mars, the same is likely true of those early ecosystems. As our only known example of early life, microbial ecosystems on Earth are our best analog as we attempt to identify and interpret biosignatures on Mars. On Earth, these early microbial ecosystems set life on its evolutionary trajectory and have influenced key geochemical cycles and sedimentary processes throughout Earth history. Silica is one of these key geochemical cycles, controlling our climate along with the carbon cycle, and siliceous sedimentary deposits (chert) preserve one of the best records of early life on Earth. As such, silica and the chert-hosted fossil record are a critical component of our understanding of the early biosphere and the coevolution of life and the planet. However, there are major outstanding questions surrounding the evolution of the silica cycle, the mechanisms of silicification, and the role of early ecosystems in shaping the silica cycle. I combine experimental geobiology with spatially-resolved analyses of chert-hosted biosignatures to better characterize early life and its evolution, the evolution of the silica cycle, and the role of microbes in shaping the silica cycle and the planet. In this talk, I will described how cyanobacteria and organic-cation-silica interactions drive silicification and suggest that cyanobacteria may have played a critical role in the Proterozoic silica cycle. I will uncover insights into Proterozoic primary producers, their physiology, and adaptations to environmental stresses that help us better characterize the Proterozoic biosphere. Finally, I will extend these findings to help search for potential silica-hosted biosignatures on Mars. Through these studies, we can better characterize the coevolution of early life and our planet and perhaps extend these insights to early life on Mars, if it ever existed.
Unravelling records of complex geobiological processes with stable isotopes and organic biomarkers
March 12, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Benjamin Uveges - Cornell University
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The bulk of our understanding of biotic and Earth system evolution derives from geochemical signatures preserved in sedimentary and fossil records. However, our ability to deconvolve the complex environmental and biological processes contributing to these geobiological archives is often hindered by a disparity between the timeframes over which they occur, and the resolution at which we can make measurements. My research combines an array of stable isotopic, organic biomarker, and numerical modeling approaches to tease out a more detailed view of biogeochemical processes operating over a range of timescales. Further, I have worked to develop analytical techniques that push the boundaries of the resolution and concentration at which we can measure the stable isotopic ratios of carbon and nitrogen in an array of sample matrices. In this seminar I will demonstrate how I have applied these techniques to better understand the exotic nitrogen cycling of Mesozoic Oceanic Anoxic Events, and characterize the tumultuous path to an oxygenated atmosphere during the Great Oxidation Event, along with my plans for future research.
Searching for novel dark energy metabolisms: thermodynamics-guided cultivation of microbial life from the subsurface biosphere
March 18, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Heidi Aronson - UC Berkeley
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Microbial life dominates Earth's phylogenetic and metabolic diversity, with most of it residing in energy-limited marine and terrestrial subsurface environments. Despite their influence on global redox cycling and ecosystem function, anaerobic subsurface microorganisms remain largely uncultured and poorly characterized. The unknown physiologies of these microorganisms likely involve a wide diversity of novel or obscure metabolic reactions that are not accounted for in our estimations of subsurface energy flux and biogeochemical dynamics. Using a thermodynamics-guided cultivation approach, my research investigates three novel microbial metabolic reactions—sulfur comproportionation, sulfur disproportionation, and phosphite oxidation—spanning scales from microbial physiology to elemental cycles. By integrating systems energetics, field research, geochemistry, genomic sequencing, laboratory-based cultivation, and multi-isotope analyses, I study how the feedbacks between these microorganisms and their subsurface environments shape biogeochemical cycling and push the boundaries for the limits of life on Earth.
Uncovering the carbon cycle of anoxic environments
March 19, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Elliott Mueller - University of Colorado
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For the first two billion years of Earth history, microbial life and our planet coevolved under an anoxic atmosphere. Today, microbial communities abound in anoxic environments — like the continental and marine subsurfaces — where they actively cycle carbon and nutrients. These facts demonstrate that sustainable biospheres do not require molecular oxygen to thrive. Indeed, our best hopes for finding life beyond Earth likely lie with planets and moons that may be anoxic as well. Despite the importance of anaerobic microorganisms to planetary evolution and astrobiology, there are major open questions surrounding their influence on Earth’s carbon cycle. My research program focuses on the rates, mechanisms and limitations of anaerobic organic degradation, which is a key component of global carbon dynamics. Central in this process is microbial fermentation, a commonly overlooked anaerobic metabolism that transforms complex organic matter to simple organic acids (e.g. acetate). These organic acids are then rapidly consumed, generating potent greenhouse gases like carbon dioxide and methane. By combining method development, metabolic modeling and experimental geobiology, I harness organic acids as a window into the carbon cycle, informing the fate of modern climate, the structure of the ancient biosphere, and the potential for life elsewhere in the Solar System. In the first part of this seminar, I will present new Orbitrap mass spectrometry techniques that I have developed to measure precise isotope ratios of organic acids with unprecedented sensitivity. I will demonstrate how the isotopic signatures of organic acids identify their metabolic origins and quantify their in situ turnover rates. These analyses offer unique insights into the microbial activity of anoxic subsurface ecosystems and valuable applications to astrobiology research. In the second half, I will shift perspectives to the role of microbial fermentation on the ancient Earth. I will present isotopic signatures in lipid biomarkers that trace the activity of fermentation throughout the Proterozoic. Taken together, these studies shed light on how anoxic worlds can build sustainable and diverse biospheres.
An eventful start: The early history of animals in the Ediacaran.
March 20, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Scott Evans -
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The first evidence of abundant, complex animals is preserved among exceptionally preserved, soft-bodied fossils of the Ediacara Biota. As such, this biota represents the premier dataset for understanding the emergence and diversification of animal life on this planet. While the recognition of such fossils is critical in furthering our understanding of metazoan evolution, our view of the Ediacaran is limited by the relatively few exceptional deposits containing abundant and well-constrained examples of these unique taxa. Further, the relationships between these ancient complex life forms and modern animals are often enigmatic, leaving many interpretations contentious. Despite these limitations, global patterns support significant changes in diversity, disparity and ecological structure within the Ediacaran Biota of similar magnitude to those observed during major biotic turnover events of the Phanerozoic. These global trends are necessarily constructed from local studies, so it is imperative to understand the varied controls on these records to interpret any large-scale biotic signals. I will highlight several new advances in our understanding of the Ediacara Biota – from an extinction event to new localities and species – that help to contextualize these exceptional fossils within the broader picture of the evolution of animal life on this planet.
Arthropods in Deep Time: A Model System for Paleobiology
April 2, 2025
noon - 1 p.m.
3853 Slichter Hall
Presented By:
- Russell Bicknell -
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Arthropods (spiders, scorpions, and crabs) are the most diverse and disparate group of animals alive today, making up over 75% of known modern animals. They also have an extensive fossil record ranging from the dawn of complex life—the Cambrian—to today. Arthropod exoskeletons have evolved to meet the demands of different ecological and environmental conditions, including structures used for protection, swimming, and predation. In rare circumstances, an unprecedented level of anatomical, functional, and ecological information is preserved in the arthropod fossil record. This exceptional preservation provides us with the data needed to evidence form, function, and ecology in fossil forms. My research leverages exceptionally preserved material to reconstruct extinct predators in 3D, and combines these models with computational methodologies (e.g., 3D finite element analyses, kinematics) to advance the modern synthesis of paleobiology. In doing so, I highlight that examination of extinct arthropods has dramatically expanded how we understand biological processes within a deep time context.