Continental uplift, subsidence and topographic scaling: Some implications for the history of mantle convection
Histories of mantle convection have implications for understanding most geological processes including lithospheric uplift and subsidence, stratigraphy and distribution of natural resources, and magmatism. Geodynamic models of mantle convection are now complex and predict a range of time-dependent phenomena (e.g. upwelling sheets, plumes, spokes and downwellings). Whilst theory used to explain mantle convection is advanced, the observational database that constrains its evolution is scant. In a few places, such as the North Atlantic Ocean, geochemical and geophysical observations combine to convincingly constrain a history of mantle convection. These observations indicate that convection there is time-dependent. Its evolution affects asthenospheric temperatures, which control plate thicknesses and strength, regional uplift and subsidence, and the chemistry and volume of magmatism. In contrast, the observational database for continental regions is sparse. The continents offer both a challenge and an opportunity. An obvious challenge is that, compared to the oceans, continental lithosphere and its relationship to sub-plate processes are poorly understood. An opportunity is that we can make a suite of geological and geomorphological observations that constrain its evolution on a range of length and timescales. I will show examples of observations that constrain histories of sub-plate support at passive margins. And how drainage patterns can be used to invert for continental-scale uplift and erosion histories, which help to fill in gaps between spot measurements of uplift and denudation. Spectral analyses of drainage patterns goes some way to explaining why simple erosional models can be used to predict uplift, denudation and sedimentary flux histories. I will show examples of how these observations and models can be combined with major element chemistry of extrusive mafic magmatism and shear wave tomography to constrain histories of asthenospheric support.
https://www.munich-geocenter.org/events/seminars/frontiers-in-earth-sciences-23/frontiers-in-earth-sciences-2019-06-14
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Continental uplift, subsidence and topographic scaling: Some implications for the history of mantle convection
Abstract
Histories of mantle convection have implications for understanding most geological processes including lithospheric uplift and subsidence, stratigraphy and distribution of natural resources, and magmatism. Geodynamic models of mantle convection are now complex and predict a range of time-dependent phenomena (e.g. upwelling sheets, plumes, spokes and downwellings). Whilst theory used to explain mantle convection is advanced, the observational database that constrains its evolution is scant. In a few places, such as the North Atlantic Ocean, geochemical and geophysical observations combine to convincingly constrain a history of mantle convection. These observations indicate that convection there is time-dependent. Its evolution affects asthenospheric temperatures, which control plate thicknesses and strength, regional uplift and subsidence, and the chemistry and volume of magmatism. In contrast, the observational database for continental regions is sparse. The continents offer both a challenge and an opportunity. An obvious challenge is that, compared to the oceans, continental lithosphere and its relationship to sub-plate processes are poorly understood. An opportunity is that we can make a suite of geological and geomorphological observations that constrain its evolution on a range of length and timescales. I will show examples of observations that constrain histories of sub-plate support at passive margins. And how drainage patterns can be used to invert for continental-scale uplift and erosion histories, which help to fill in gaps between spot measurements of uplift and denudation. Spectral analyses of drainage patterns goes some way to explaining why simple erosional models can be used to predict uplift, denudation and sedimentary flux histories. I will show examples of how these observations and models can be combined with major element chemistry of extrusive mafic magmatism and shear wave tomography to constrain histories of asthenospheric support.
