Unpicking global mantle convection influences from the local: investigating asthenospheric versus lithospheric constraints on the evolution of

Unpicking global mantle convection influences from the local: investigating asthenospheric versus lithospheric constraints on the evolution of landscapes

This study will examine the role large-scale, global, mantle convection patterns might play on the long-term development of the Earth's landscape, versus higher-resolution, localised studies that focus on features of basal architecture of the lithosphere, or presence of subducted slabs (e.g. Kaislaniemi & van Hunen 2014). Much of the debate around long-term landscape evolution, centres around lithospheric response to dynamics of the mantle beneath, versus the architecture of the lithosphere itself, or its history of loading or heating (e.g. Wheeler & White, 2002).
Both geophysical and numerical studies on global mantle structure reveal broad-scale convection patterns that show the flow of mantle beneath plates (e.g. Barry et al., 2017), but such studies do not include higher resolution details, such as asthenospheric interactions with the irregular base of the lithosphere, or localised disrupted flow patterns around downwelling slabs (e.g. Xu & Zhao, 2009; Zahirovic et al., 2016). Nor do they take account of dynamics within the lithosphere, such as basin development or regions of uplift.
This project will look at three contrasting regions, which characterise different complexities of flow regimes within the shallow mantle: east Africa - an intraplate setting dominated by a large-scale mantle upwelling and lacking subducted slabs within the shallow mantle; south-east Asia - an area dominated by the complex interaction of downgoing slabs and ongoing subduction; and central Asia - an intraplate area with no obvious large-scale plume or active subduction but has slabs deep within the upper mantle from former subduction events (Figure 1).
All these areas have a wealth of information about the nature of the landscape development, with information about the timing and extent of basin development, regions of uplift, details of distribution of magmatism deriving from the mantle, and detailed geophysical constraints on the architecture of the lithosphere. This project will examine how much the presence of slabs influences local mantle convection patterns over global patterns. How much does a mantle plume upwelling influence localised flow at the base of the lithospheric mantle? And how much does the resultant mantle flow influence the evolving landscape above it, with development of basins or upland areas?