Events

DeFord Lecture | Isaiah Bolden

Biogeochemical Fingerprints of Change in Coral Reef Ecosystems Across Space and Time by Isaiah Bolden, Georgia Tech

Abstract: Coral reef ecosystems are known to be in a global state of decline, largely attributed to sea-surface warming, ocean acidification, pollution, disease, and other direct human contributions. The impending transition away from calcified substrates to macroalgae dominance and other alternative stable states within these environments could translate to major losses in marine biodiversity, erosion of protective coastal barriers, stress on major fisheries, and numerous other sociocultural and economic impacts. My research combines discrete and autonomous measurements of carbonate chemistry, trace metal, and carbon isotope variability within coral reef environments, quantitative decomposition models of biogeochemical fluxes within reefs, and high-resolution mass spectrometry to investigate various geochemical proxies as fingerprints of stress-induced changes in reef metabolism and community composition. I also apply similar tools to understand the utility and nuances of coral skeletons as paleoclimate archives in modern and ancient reef ecosystems. Here, I will primarily report on (1) the use of temporal variability in modern reef seawater Sr/Ca ratios as an indicator of calcifier community composition shifts under compounding environmental stressors and (2) ongoing efforts to construct comprehensive paleoclimate records of Southern Caribbean temperature and aridity using co-located coral skeleton and speleothem geochemical analyses. The ultimate aim of research in my group is to build and apply sophisticated analytical and quantitative tools for detecting and monitoring environmental change on reefs and better protect the ecosystem services these dynamic environments provide.

DeFord Lecture Series
Since the 1940’s, the DeFord (Technical Sessions) lecture series, initially the official venue for disseminating EPS graduate student research, is a forum for lectures by distinguished visitors and members of our community. This is made possible through a series of endowments.

UTIG Seminar Series: AGU Special! Charles Babendreier & Eric Hiatt

Speaker: Charles Babendreier, Graduate Research Assistant, University of Texas Institute for Geophysics

Host: Shuoshuo Han

Title: Massive submarine landslides imaged offshore southern Oregon

Abstract: Submarine landslides are gravity-driven, mass transports that occur beneath the sea surface along the slopes of underwater geologic features (e.g., continental slopes, submarine canyons). In some cases, submarine landslides can destroy valuable ocean bottom infrastructure and/or generate tsunamis, posing risk to nearby coastal communities. At the Cascadia Subduction Zone off the west coast of the U.S. and Canada, the oceanic Juan de Fuca Plate slides beneath the continental North American Plate. Previous bathymetric and seismic imaging have shown that submarine landslides are ubiquitous along the Cascadia margin. In 2021, new multi-channel seismic data were acquired onboard the R/V M. G. Langseth using a 12 km hydrophone streamer and a 6600 in3 airgun source through the CAscadia Seismic Imaging Experiment 2021 (CASIE21). Using this dataset, we have an unprecedented opportunity to map the buried deposits of submarine landslides and characterize their structure along this margin. We identified 10 massive submarine landslide deposits offshore southern Oregon (latitudes 42°-44° N). Landslide deposits of this scale are not observed elsewhere along this margin. Two of the older deposits, both near 44° N, have the largest spatial extent. They are imaged over 55 km seaward of the deformation front and cover an estimated area of 17000 km2 and 7430 km2, respectively. The mean estimated surface area of the other eight events is 470 km2. Six of the ten observed slides exhibit compressive thrust features contained mostly within the seaward portion of the deposit. These are interpreted to be zones of impact-induced deformation from the slide material. Six of the ten deposits also contain at least one distinct region of high-amplitude, semi-coherent reflections, which we interpret to indicate detached slide blocks. Our observations from the seismic images suggest that most of these slides failed and displaced as cohesive bodies with high seafloor impact-velocities. Given the size and style of deformation of these deposits, some of these events could have generated great tsunamis. We will conduct stratigraphic analysis and integrate existing ocean drilling data to determine the age of these landslide events and investigate their impact on wedge evolution and tsunami hazards in this region.

Speaker: Eric Hiatt, Graduate Research Assistant, University of Texas Institute for Geophysics

Host: Sean Gulick

Title: Limited Recharge on Early Martian Aquifers: Numeric & Analytic Recharge Rate Estimates As Constrained By Geomorphic and Geochemical Observations

Abstract: The surface of Mars shows past evidence for liquid water at its surface, however the time water remained and its volume remain open questions. In this work, we derive an idealized mathematical solution for an equation often used to study groundwater flow on Mars. We use this solution to analyze and validate a computer model based solution in a configuration that reflects the geometry associated with a planet scale problem. We use publicly available elevation data to populate our model as well as Martian shoreline elevations proposed in previous works. This allows us to investigate possible combinations of shorelines and recharge rates that produce model outputs that resemble observations made on Mars. Large volumes of work have been produced to characterize the deposition and erosional history of landforms on Mars. There is general consensus that specific Martian terrains show evidence that make groundwater upwelling more likely. The same is true regarding groundwater sapping. We use these studies to eliminate model combinations that either produce upwelling or sapping in areas without evidence for these processes. In doing so, we find that recharge rates published in the literature are ten to one hundred times higher than our model predictions.

DeFord Lecture | Julia Cisneros

The morphology of alluvial sand dunes

Abstract: In the process of sediment transport through a shearing flow, dunes are forming and simultaneously recording their surrounding conditions. These records offer clues about the movement of wind and water across an ancient, otherwise unknown, landscape. In turn, dunes are influencing how sediment is transported. Key to leveraging these records of ancient environments is our understanding of the links between flow, sediment transport, and bedform morphodynamics. To gain that critical understanding, we use modern bedforms to understand the conditions of the Earth and planetary systems and improve how contemporary environments are managed.

This talk will highlight research that aims to investigate dune formation and dune shape in big and small rivers and in shallow laboratory flows. This investigation allows the comparison and validation of the key processes controlling the formation of low-angle dunes. I then identify and discuss the conditions when one process may dominate in creating complex dune shapes. This talk highlights the balance between bedform superimposition and sediment suspension as controls on the formation of low-angle dunes. This information is vital to improving our approach to managing contemporary rivers under modern stressors and revealing the deposits of ancient rivers.

DeFord Lecture Series
Since the 1940’s, the DeFord (Technical Sessions) lecture series, initially the official venue for disseminating EPS graduate student research, is a forum for lectures by distinguished visitors and members of our community. This is made possible through a series of endowments.

DeFord Lecture | Jonathan Ajo-Franklin

Exploring the Subsurface with Regional DAS Networks: Results from the Imperial Valley Dark Fiber Project by Jonathan Ajo-Franklin, Rice University

Abstract:With recent advances in the large-scale deployment of distributed acoustic sensing (DAS) approaches utilizing telecommunication infrastructure, the asymmetry between the per-channel cost of high-resolution passive seismic recording and corresponding active source deployments continues to increase. This has motivated renewed interest in both large-scale ambient noise studies as well as improved utilization of shallow natural seismicity for imaging applications. In this study, we highlight three approaches for using DAS, ambient noise, and shallow earthquakes to constrain larger scale S-wave velocity and reflectivity structure utilizing data acquired as part of the Imperial Valley Dark Fiber Project (IVDFP). The project targets structures near the Brawley Geothermal Field relevant to understanding the seismic signatures of hidden geothermal systems; to date, almost 19 months of continuous DAS data has been acquired on a 27 km (7000+ channel) dark fiber array stretching from Calipatria to Imperial, CA. In our first example, we show on-going work seeking to combine the high spatial density of DAS and anthropogenic ambient noise imaging to constrain zones of hydrothermal alteration directly beneath the Brawley field. In the second example, we attempt to utilize the abundant natural seismicity in the Brawley Seismic Zone (BMZ) recorded by DAS, and local earthquake tomography to improve constraints on S-wave structure over a larger region. In the third example, we image large lateral reflectivity features near the field using coherently scattered S-waves and 3D migration, an approach not possible using the classical sparse seismic arrays. These results are compared to existing datasets and interpreted to be related to deep hydrothermal alteration and fault-related structures at the southern termination of the Brawley Seismic Zone (BSZ).
Further information in: Ajo?Franklin, J., Rodríguez Tribaldos, V., Nayak, A., Cheng, F., Mellors, R., Chi, B., Wood, T., Robertson, M., Rotermund, C., Matzel, E. and Templeton, D.C., 2022. The Imperial Valley Dark Fiber Project: toward seismic studies using DAS and telecom infrastructure for geothermal applications. Seismological Society of America, 93(5), pp.2906-2919.

DeFord Lecture Series
Since the 1940’s, the DeFord (Technical Sessions) lecture series, initially the official venue for disseminating EPS graduate student research, is a forum for lectures by distinguished visitors and members of our community. This is made possible through a series of endowments.

Doctoral Defense | Natchanan (Mint) Doungkaew

The final doctoral examination for NATCHANAN (MINT) DOUNGKAEW is scheduled for DECEMBER 9; 1:00 PM; JGB 4.102 (Barrow Family Conference Room) and VIRTUAL.

The PhD project ” Fracture Growth In Chemically Reactive Geologic Systems: Experimental And Field Studies” was supervised by Dr. Peter Eichhubl.

Committee members include: Drs. Nicola Tisato, Mark A Helper, James E Gardner, David N Espinoza

The defense is open to all members of the University community and the public.

ZOOM link: https://utexas.zoom.us/j/93225848830

Alumni Reception at AGU in Chicago

Join the Jackson School of Geosciences for an alumni reception at AGU’s annual meeting in Chicago.

WHEN: Wednesday, December 14 | 12:00pm – 2:00pm 
WHERE: Fatpour TapWorks McCormick