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ESS Department - April 25th, 2024
Will Hoover - "Chemo-mechanical evolution of a slow slipping subduction interface" Abstract: Episodic tremor and slow slip is an enigmatic component of the seismic cycle that occurs at the fluid-rich subduction interface down-dip of the seismogenic zone. Fluid-driven chemical reactions in this interface produce talc-, chlorite- and amphibole--rich rocks that modify its rheology, however we know little about how they influence episodic tremor and slow slip. I will reconstruct the evolution of an exhumed subduction interface shear zone from the depths of modern episodic tremor and slow slip, and show that talc-rich rocks hosted slow slip deformation and should not be overlooked in models of the seismic cycle. Tsai-Wei Chen - "Temperatures of Vein Formation Associated with Plate Interface Deformation Constrained by Oxygen and Clumped Isotope Thermometry" Abstract: In this talk, I will begin by introducing my research on quartz-calcite...
ESS Department - April 18th, 2024
Constraining the age of collision between the Kohistan-Ladakh arc (KLA), an intra-oceanic arc remnant, and Eurasia along the Shyok suture zone is critical to understand the development of the India-Eurasia orogenic system. Estimates of the timing of KLA-Eurasia collision span 100 – 40 Ma, permitting conflicting tectonic scenarios in which the KLA either collided first with Eurasia or first with India. Each of these scenarios has very different implications for how India-Eurasia convergence was accomodated and the linkages between Himalayan orogenesis and global climate change in the Cenozoic. In this talk I will present field observations, structural analyses, and U/Pb zircon ages that constrain the tectonostratigraphy and structural development of the Shyok suture zone in Ladakh, NW India. These results support multi-stage arc-continent accretion models for the India-Eurasia collision because they show that KLA-Karakoram collision likely...
ESS Department - April 11th, 2024
Ice-infiltrated sediment, or frozen fringe, is responsible for phenomena such as frost heave, ice lenses and meters of debris-rich ice under glaciers. Understanding frozen fringes is important as frost heave is responsible for damaging infrastructure at high latitudes and sediment freeze-on at the base of glaciers can modulate subglacial friction, influencing the rate of global sea level rise. Here we describe the thermomechanics of liquid water flow and freezing in ice-saturated sediments, focusing on the conditions relevant for subglacial environments. The force balance that governs the frozen fringe thickness depends on the weight of the overlying material, the thermomolecular force between ice and sediments across liquid premelted films and the water pressure required by Darcy flow. We combine this mechanical model with an enthalpy method that conserves energy across phase change interfaces on a fixed computational grid. The force balance...