Title:Understanding Earth’s paleoenvironmental evolution (on long timescales)

Abstract: Animals originated and evolved during one of the most unique times in Earth history—the Neoproterozoic Era—and early animal evolution has long been causally linked to environmental change during this interval. However, geochemical patterns of change are often noisy, and no stratigraphic section covers the entirety of Earth history; global database studies are required. Here, data from the Sedimentary Geochemistry and Paleoenvironments Project (SGP) will be used to demonstrate how machine learning methods and increased emphasis on accounting for sampling bias can yield a more resolved pattern of environmental change in deep time. The talk will also discuss the prospects and pitfalls of ‘team science’ approaches in the geological sciences. The results suggest that early animals evolved in a Neoproterozoic world that had lower oxygen levels and lower primary productivity than the Paleozoic, although the magnitude of oxygen change at the dawn of the Phanerozoic was likely less than commonly hypothesized. Finally, ecosystems along modern natural gradients of oxygen and primary productivity will be used to conceptualize Neoproterozoic ecosystems and deduce the possible role of environmental change in the Cambrian ‘explosion’ of animal life. 

*Please note that this lecture will not be recorded or posted after. 

Title: The life and times of a ferruginous lake

Abstract: Permanently stratified lakes that are also ferruginous (i.e. abundant dissolved iron) are biogeochemical hot spots for (microbial) redox transformations of major and trace elements. Across such an interesting set of gradients (light, oxygen, temperature, salinity, nutrients, etc.), there is really something to interest every flavor of biogeochemist. In this talk I will discuss one modest little lake in northern Minnesota that has given us some real insights into how ferruginous aquatic conditions function and the geochemical records they might leave behind. This is of particular interest to geoscientists who want to better understand how biogeochemical cycles operated in the Archean and Proterozoic oceans. Lakes aren’t oceans, though, and so I will address both the applications and limits of this analogy.

*Please note that this lecture will not be recorded or posted after. 

Title: Why do Great Continental Earthquakes Nucleate on Branch Faults?

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Title:Uranium Isotopes as Tracers of Seafloor Weathering

Abstract:The oceanic crust and marine sediments are exposed to pure and chemically altered seawater. Fluid-rock interactions between these reservoirs provoke a wide variety of chemical reactions that modify the physical and chemical properties of both the fluids and the solids involved, with implications for the global cycles of water, carbon dioxide, and fluid-mobile elements in Earth’s surface and interior. Uranium is a powerful tracer of weathering reactions at the seafloor because it is highly soluble in its oxidized form in seawater, and undergoes two flavors of isotopic fractionation: one during water-rock interaction, and one during redox transitions between U(VI) and U(IV). In this talk, we show how uranium isotopes can be used to fingerprint weathering dynamics in serpentinites and in marine sediments. We use our results to show that low-temperature weathering of oceanic serpentinites by chemically evolved seawater is pervasive at the seafloor, and that continental serpentinites host unique uranium isotope signatures driven by the grain size of U hosting minerals. We investigate the role of iron oxides as mineralogical hosts for uranium in seafloor serpentinites and discuss possible implications for the whole-earth uranium isotope cycle

Title:"Road Trip! Jay Quade, Field Geology, Geochemistry" Presented by Thure Cerling

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Title: Ontogenies of Orogenies and Erodibilities of Landscapes

Abstract:Understanding how erosion rates are influenced by tectonics, climate, and lithology is crucial for interpreting the evolution of Earth’s topography. The rate of rock uplift is one of the primary controls on erosion rate. Mountain ranges adjust to changes in uplift rate by adjusting their steepness so that erosion rates balance the rates of rock uplift. The amount that a landscape needs to steepen to achieve an erosion rate that balances the rate of rock uplift depends on multiple factors that control the efficiency of erosion, such as rock erodibility. Previous research has investigated the influence of erodibility on the relationship between erosion rates and landscape steepness by analyzing erosion rates and steepness values across catchments with varying fracture densities. These studies have shown that catchments with higher fracture densities exhibit greater erodibility and require less channel steepness to achieve a given erosion rate compared to catchments with lower fracture densities. However, the possibility of erodibility variations across different stages of mountain building (ontogeny) on a continental scale has yet to be directly investigated. In this talk, I will present results from ongoing research on the relationship between erosion rates derived from ¹⁰Be cosmogenic nuclides and channel steepness across orogens of different ages in the conterminous United States. Rock erodibility is expected to have a relationship with orogen age following from the general observation that during orogenesis, cooler, upper crustal rocks experience greater amounts of brittle strain than warmer, more ductile rocks at depth, creating a ‘fracture stratigraphy’. This fracturing process is expected to reduce the erodibility of the upper crust in young and tectonically active orogens. In contrast, areas that have not recently experienced intense deformation (i.e., tectonically quiescent), should have lower fracture densities.

Watch the lecture here.

Pistone is the Geological Society of America's Continental Scientific Drilling Division  2024-2025 Distinguished Lecturer.

Title: Moho Mission to the Foundation of Continents: The ICDP DIVE Drilling Project.

Abstract: It is more difficult to access the Earth’s interior a few miles below our feet than it is to explore the surface of another planet hundreds of thousands to million miles away. Drilling has made it possible to explore the Earth’s interior and thus, go deep. But the thrill to drill is quickly contrasted by the challenging pressure exerted by the rocks with increasing depth. Since Project Mohole in the 1960s, scientists have worked to reach the boundary between the crust and the mantle known as the Moho. This boundary representing the foundations of continents is usually beyond the reach of our present-day technology. However, in some places on Earth, it is possible to reach the crust-mantle frontier without going as deep. The Ivrea-Verbano Zone in the Italian Alps is the golden target to explore the crust-mantle transition zone in less than 1 mile depth. This is because the collision between tectonic plates that generated the European Alps brought the crust-mantle boundary to a shallow depth and thus, under conditions of low pressure, present-day drilling technology can sustain a borehole to this depth. Based on the collaborative effort led by more than 50 scientists, I will present the major outcomes of Phase 1 of the ICDP DIVE (Drilling the Ivrea-Verbano zonE) project tackling key questions related to the chemistry and architecture of the crust-mantle transition, the geophysical signatures, and insights into the deep biosphere.

Title: Multi-Scale Structure and Dynamics in Earth’s Lowermost Mantle.

Abstract:In Earth’s deepest mantle, there are two huge structures with anomalously lower seismic velocities than their surroundings. They are often called “Large Low Shear Velocity Provinces” or LLSVPs. These vast structures, potentially distinct in composition, are dynamic imprints of Earth’s 4.5-billion-year evolution. Their morphology and physical-chemical properties hold critical clues to the planet’s internal processes, from deep mantle convection to the cycling of materials over geological timescales. Besides these large-scale structures, seismic observations reveal widespread small-scale heterogeneities, including ultra-low velocity zones (ULVZs). These ULVZs, characterized by even lower seismic velocities, are found both inside, outside, and along the margins of LLSVPs, suggesting a complex and dynamic deep mantle environment. Here, I will discuss results about the formation, dynamics, and evolution of these multi-scale structures. Our findings provide insights into the interactions between LLSVPs, ULVZs, mantle plumes, and subducted materials, shedding light on the role of the lowermost mantle in driving Earth’s long-term thermochemical evolution.

Title: Role of Old-aged Groundwater in a Mountain Watershed - Application of Environmental Age Tracers and an Integrated Hydrologic Model.

Abstract: Headwater mountain systems provide an outsized proportion of the water resources throughout the Western United States. However, the role of bedrock groundwater in mountain hydrologic processes is largely unknown and poorly quantified. For instance, it remains uncertain how much groundwater is stored in headwater systems, the timescales over which groundwater moves through fractured bedrock, its role in headwater streamflow generation, and how it may be impacted by climate change. In this work we utilize observations of environmental age tracers, mountain groundwater levels, and high-performance integrated hydrologic modeling and particle tracking to quantify bedrock groundwater storage and stream discharge dynamics in the mountainous East River Watershed, Colorado (USA). Our combined observational and numerical modeling approach aims to elucidate the role of groundwater in streamflow generation within this high-elevation mountain watershed. We find that the release of old-aged groundwater storage is vital for sustaining streamflow, especially in the presence of low-snow years. However, this buffering of streamflow with groundwater may be temporary, as both simulated and observed groundwater level timeseries show declines over the past 7 years, suggesting a potential unsustainable loss of groundwater storage with unknown impacts on future streamflow. These results emphasize the importance of understanding the processes governing groundwater recharge, discharge, and storage changes in high-elevation mountains for effective management of downstream water resources.