Events

Bureau of Economic Geology Seminar Series

DeFord Lecture | Dr. Roger Creel

Retreat, Regrowth, and Rapid Thinning: Reconstructing the Holocene History of the Antarctic Ice Sheet by Dr. Roger Creel, Department of Geology and Geophysics, Texas A&M University

Abstract: Understanding how the Antarctic Ice Sheet changed during past warm periods helps us project how fast Antarctica may shrink during the 21st century. The research I will present constrains Antarctic Ice Sheet change during the Holocene (11.7 – 0 thousand years ago), which is the last time global temperatures may have exceeded early Industrial (1850 CE) values. I will first estimate the Antarctic contribution to Holocene global mean sea level via a statistical framework that merges glacial isostatic adjustment models with observations of past sea level and nearfield Antarctic constraints. This estimate requires constructing the first quantitative estimates of Holocene mountain glacier volume and sea level change due to ocean thermal expansion, which I will discuss. I will then use cosmogenic nuclide exposure ages and marine sedimentary data to reconstruct how Antarctica thinned during the Holocene. I will close by comparing Antarctica’s Holocene history to modern and future trends to give perspective on the response of our largest ice sheet to warming.

UTIG Seminar Series: Weisen Shen, Stony Brook University

Speaker: Weisen Shen, Stony Brook University

Host: Duncan Young & Chuanming Liu

Title: Seismic architecture of the deep continental crust and its implications

Abstract: Thermal, chemical, and isostatic properties of continental lithosphere play critical roles in understanding the geological evolution and continental dynamics of the Earth. For polar regions like Greenland and Antarctica, knowledge of these properties is required to develop better understanding on how their icesheets react to the changing climate. In contrast to this importance, our assessment to these properties, especially for the deep crust, have been indirect and subject to high uncertainties. The seismic architecture of the deep crust (e.g., Moho topography, seismic velocities and their ratios) provides a unique window to constrain these properties. In this talk, I will present some recent progress in constraining and interpreting the seismic properties such as Moho and velocities of deep crust of the United States and Antarctica. The progress allows a more accurate determination of thermal and rheological properties of the continents, and brings in the potential to quantify the polar ice-sheets’ response to the changing climate.

Bureau of Economic Geology Seminar Series

DeFord Lecture | Dr. Marjorie Cantine

Matters of Time: Controversy, Correlation, and the Dating of Sedimentary Records by Dr. Marjorie Cantine, College of Environment, Department of Earth and Space Sciences, University of Washington

Abstract: Time is a master variable in the Earth sciences, key to calculating rates and fluxes, drawing causal relationships between events, and determining the frequency of events. The importance of time motivates us to try and quantify it in sedimentary records of Earth’s changing life and environments. In this talk, I’ll discuss some of the geological and analytical challenges at the frontier of telling time in Earth’s complex surface environments and share the progress that my research group is making in dating the rise of animals on the Precambrian Earth.

UTIG Seminar Series: Jim Hurrell, Colorado State University

Speaker: James (Jim) Hurrell, Colorado State University

Host: Danielle Touma

Bureau of Economic Geology Seminar Series

DeFord Lecture | Dr. Manuele Faccenda

Central Mediterranean Structure and Dynamics From Combined Geodynamic and Seismological Modeling by Dr. Manuele Faccenda, Department of Geosciences, Università degli Studi di Padova, Padova, Italy

Abstract: The Tertiary tectonic evolution of the Central Mediterranean and its first-order present-day structure have been relatively well constrained by abundant geological and geophysical data. Yet, several uncertainties persist about the mechanisms that led to the present-day surface morphology and deep slab geometry. With this respect, over the past few years new geodynamic and seismological modeling techniques have been combined to reproduce the recent large-scale evolution of the Central Mediterranean and provide mechanical constraints through the mapping of seismic anisotropy. The geodynamic simulations were designed and calibrated according to paleogeographic-tectonic reconstructions and seismological observations available in the literature. It is found that, although the opening of back-arc extensional basins in response to the retreat of the Ionian slab is a common feature in all models, structural heterogeneities within the Adria plate and/or the geometry of its Tyrrhenian passive margin profoundly impact on the segmentation of the subducting slab and the amount of Ionian trench retreat. This scenario is supported by anisotropic P-wave travel-time and S-wave splitting-intensity tomography models of the upper mantle covering the entire Mediterranean basin. The isotropic component of our preferred tomography model is dominated by numerous fast anomalies associated with retreating, stagnant, and detached slab segments. In contrast, relatively slower mantle structure is related to slab windows and the opening of back-arc basins. The anisotropy patterns are interpreted as the result of asthenospheric material flowing primarily horizontally around the main slabs in response to pressure exerted by their mid-to-late Cenozoic horizontal motion, while sub-vertical anisotropy possibly reflects asthenospheric entrainment by descending lithosphere.

The last part of the seminar is then dedicated to the discussion of a recent, stochastically-based, anisotropic tomographic model of the Etna volcanic field (Sicily, Italy), where a cylindrical pattern of P-wave slow axes is imaged in the 6-16 km depth range. According to the predictions of geodynamic modeling, this peculiar and unprecedently imaged structure should be primarily related to a radially distributed vertical dikes departing from a pressurized magma chamber.

UTIG/BEG Seminar Series: Gene Humphreys, University of Oregon

NOTE: This seminar is hosted jointly with the Bureau of Economic Geology and will be held at 3pm. The seminar will be followed by a reception in the first floor UTIG lobby at 4pm.

Speaker: Gene Humphreys, University of Oregon

Host: Thorsten Becker

Title: The Columbia River flood basalts– plume-triggered delamination and lithospheric reconstruction

Abstract: The Columbia River flood basalts present the interesting case of Yellowstone plume interacting with both subducting slab and North American lithosphere. The flood basalt’s eruptive distribution and intensity were strongly controlled by a piece of plume-destabilized lithosphere. In particular, this lithosphere delaminated when Yellowstone melt separated it from North America, and the delaminating lithosphere drew Yellowstone plume (and uplift and volcanism) rapidly northward. The uplift and lithospheric weakening caused crustal extension (gravitational collapse), which in turn enabled abundant diking and intense volcanism.

The first stage of continental construction occurs with addition of basalt to the crust; subsequent melting can segregate the basalt into granitic rock and residuum, and the residuum can eventually sink back into the mantle. As it turns out, the delamination removed lithosphere from beneath an older (Cretaceous) granite-residuum pair, allowing the residuum to sink. This drove uplift of the granitic Wallowa batholith, and the evacuated lower crust drove crustal flow into the volume beneath the batholith.

Maybe the main lesson here is that plumes and lithospheres are each gravitationally unstable, and in an inherently complicated continental environment, many interactive gravitationally unstable processes are likely to occur and even accentuate each other.

Hot Science - Cool Talks: "The Future of Texas Water"

Texas is no stranger to extreme weather, but how will climate change shape our water supply in the years ahead? In the next Hot Science – Cool Talks, Dr. Robert Mace dives into the future of Texas water, exploring how careful planning, conservation, and resilience are key to sustaining our communities through dwindling aquifers and unpredictable droughts. With water shortages affecting everyone—because we all depend on it—this discussion will highlight the biggest challenges and innovative solutions to ensure Texas has enough water for generations to come. In partnership with the Barton Springs-Edwards Aquifer Conservation District.