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Department of Earth Sciences

 
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A collection of all the seminars going on at the Department, either on the downtown site, or out at the Bullard Laboratories
Updated: 1 day 17 hours ago

Tue 22 Nov 12:00: Title to be confirmed

Wed, 21/09/2022 - 12:32
Title to be confirmed

Abstract not available

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Tue 15 Nov 12:00: Title to be confirmed

Wed, 21/09/2022 - 12:31
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Tue 08 Nov 12:00: Raising the Colorado Plateau – tales from xenoliths and petrological modeling

Wed, 21/09/2022 - 12:29
Raising the Colorado Plateau – tales from xenoliths and petrological modeling

High-elevation, low-relief continental plateaus are major topographic features and profoundly influence atmospheric circulation, sediment transport and storage, and biodiversity. Although orogenic surface-uplift mechanisms for modern continental plateaus near to plate margins, such as Tibet, are well-characterized, they cannot account for examples in intracontinental settings, such as the Colorado Plateau, southwestern USA . While strongly debated, most competing hypotheses that account for Cenozoic uplift of the Colorado Plateau acknowledge the importance of northwest-directed subduction of the Farallon oceanic plate beneath North America since c. 100 Ma. Here, I will describe the results of two in-depth investigations into mechanisms that may have caused uplift of the plateau; one being primarily tectonic, and the other being primarily petrological in nature. First, I show via study of lawsonite-bearing eclogite xenoliths collected from diatremes in the center of the plateau that the shallow-dipping Farallon slab may have penetrated through the proto-plateau SCLM at relatively shallow depth (120 km), shearing away 80 km of its mantle root. This removal likely caused asthenospheric upwelling and isostatic rebound of the plateau region during the Late Cretaceous to the Eocene. Secondly, I report on the results of recent petrological modelling that has investigated whether broad-scale hydration-induced metasomatism of continental lower crust can reduce its density and increase its buoyancy sufficiently to drive isostatic uplift. With reference to devolatilization of the subducting Farallon slab, we have applied open-system reactive transport fluid-rock interaction models to determine the spatial and temporal scales over which mineralogic transformations would have taken place following the infiltration of aqueous fluids into the proto-plateau lower crust. These data show that cumulative surface uplift of over 1,000 m can be achieved by metasomatism of an initial 40-km-thick continental crust, even at relatively modest fluid infiltration rates compared to modern-day subduction zones worldwide. This petrological effect should also be considered alongside purely tectonic arguments when accounting for anorogenic uplift in intracontinental regions, without the need to invoke contributions from extraneous mechanisms that lack a priori evidence, such as mantle plume impingement.

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Tue 07 Mar 12:00: Title to be confirmed

Wed, 21/09/2022 - 12:28
Title to be confirmed

Abstract not available

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Wed 09 Nov 16:00: Structure and uplift history of the Transantarctic Mountains: a test for convective instability in the upper mantle

Tue, 20/09/2022 - 15:23
Structure and uplift history of the Transantarctic Mountains: a test for convective instability in the upper mantle

The 3000 km long Transantarctic Mountains (TAM), and adjacent Wilkes Subglacial Basin, is one of the more dramatic physiographic features of the planet. Explaining their origin and uplift has, however, been a challenge. These mountains have formed in a tensional environment, and are up to 4500 m high. Recent seismic observation show that low shear-wave speeds, typical of asthenospheric mantle, extends to shallow depths under the edge of the TAM . In the Southern TAM this anomaly can be tracked 350 km inboard of the edge of the TAM , and in the Ross Sea sector 80 km under the edge. Here we test the proposition that ductile, small-scale, convective flow in the upper mantle can drive mountain building and coeval basin formation at the Earth’s surface. The TAM present an ideal location to carry out this test for two reasons: 1. The unusually good set of geological and geophysical data to constrain both crust-mantle structure and timing of uplift. 2. Subduction has not occurred along this boundary since 500 Ma, and thus we start with a clean slate.

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Wed 12 Oct 16:00: Title to be confirmed

Tue, 20/09/2022 - 15:23
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Wed 16 Nov 16:00: Title to be confirmed

Tue, 20/09/2022 - 15:21
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Wed 09 Nov 16:00: Structure and uplift history of the Transantarctic Mountains: a test for convective instability in the upper mantle

Tue, 20/09/2022 - 15:19
Structure and uplift history of the Transantarctic Mountains: a test for convective instability in the upper mantle

The 3000 km long Transantarctic Mountains (TAM), and adjacent Wilkes Subglacial Basin, is one of the more dramatic physiographic features of the planet. Explaining their origin and uplift has, however, been a challenge. These mountains have formed in a tensional environment, and are up to 4500 m high. Recent seismic observation show that low shear-wave speeds, typical of asthenospheric mantle, extends to shallow depths under the edge of the TAM . In the Southern TAM this anomaly can be tracked 350 km inboard of the edge of the TAM , and in the Ross Sea sector 80 km under the edge. Here we test the proposition that ductile, small-scale, convective flow in the upper mantle can drive mountain building and coeval basin formation at the Earth’s surface. The TAM present an ideal location to carry out this test for two reasons: 1. The unusually good set of geological and geophysical data to constrain both crust-mantle structure and timing of uplift. 2. Subduction has not occurred along this boundary since 500 Ma, and thus we start with a clean slate.

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Thu 15 Sep 14:00: Redox processes in subduction systems Barrow Award

Mon, 12/09/2022 - 09:32
Redox processes in subduction systems

Abstract not available

Barrow Award

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Thu 15 Sep 14:00: Redox processes in subduction systems Barrow Award

Tue, 16/08/2022 - 12:33
Redox processes in subduction systems

Abstract not available

Barrow Award

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Thu 15 Sep 14:00: Title to be confirmed Barrow Award

Fri, 12/08/2022 - 17:40
Title to be confirmed

Abstract not available

Barrow Award

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Wed 07 Sep 16:00: Title to be confirmed

Fri, 12/08/2022 - 14:41
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Wed 07 Sep 15:00: Title to be confirmed

Fri, 12/08/2022 - 14:41
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Wed 07 Sep 14:00: Title to be confirmed

Fri, 12/08/2022 - 14:40
Title to be confirmed

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Wed 07 Sep 12:00: Title to be confirmed

Fri, 12/08/2022 - 14:40
Title to be confirmed

Abstract not available

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