Theme 3: Global Palaeogeography and Geodynamics
Theme Co-leaders: Dietmar Müller (Australia), Hanlin Chen (China)
3.1.1 Title: Understanding the deep driving forces of Earth’s large-scale topography through time
3.1.2 Leader(s) from different ACTER partner institutions:
3.1.3 Project description:
Aims and Background – Continents and sedimentary basins through time record fundamental Earth system cycles, reflecting environmental change, migration of fauna and flora and shifting coastlines. It was originally thought that successive advances and retreats of shallow inland seas mainly reflect global sea level variations (eustasy). It is now well known in principle that large-scale surface morphology such as the high topography of the East African Rift, the low-lying Amazon River Basin and the southwest to northeast tilt of the Australian continent are strongly controlled by processes deep within the Earth, but progress has been slow in quantifying the magnitude and time-dependence of these relationships. Advances in simulation and modelling have bolstered the view that the convecting mantle may indeed play a profound role in driving the evolution of sedimentary basins and continental interiors, in addition to smaller-scale structural reactivation that may rather be related to changes in plate boundary forces and intraplate stress fields through time.
The overarching aim of this project is to understand the deep-seated driving forces of large-scale topographic change, providing new, dynamically self-consistent, global-scale models of the Earth’s subduction history, deep plume sources and dynamic topography for the past 550 million years. By fusing geological observations with geodynamic models through space and time we seek to answer three key questions:
1. What are the long-term patterns and magnitudes of mantle-convection-driven topography?
2. How have the fundamentally different plate tectonic configurations before and after the assembly of the supercontinent Pangaea affected large-scale mantle convection flow and surface topography over the last 550 million years?
3. How are fluctuating mantle upwellings and plumes dependent on the history of subduction, and how does this interplay drive surface subsidence and uplift? Mantle convection phenomena affecting surface topography include mantle flow driven by subduction, large- scale mantle return flow, the arrival of mantle plume heads at the surface, the pulsing of mantle plumes and ephemeral upper mantle convection beneath basins. These processes result in regional uplift and subsidence of continental interiors and margins, creating or destroying sedimentary basins and modulating their evolution, but it is often not obvious how to separate their effect from eustasy. In addition, recent advances in plate tectonic reconstructions allow us to constrain the longitudinal position of continents for times pre- dating the oldest ocean floor. This breakthrough opens the opportunity of extending plate tectonic reconstructions from the last 200 Myr (million years) to the beginning of the Phanerozoic (550 Myr). So far there is no systematic understanding of how mantle processes have influenced surface elevation globally over long geological timescales (100s of millions of years). The most recent generation of numerical models, coupling plate tectonics with mantle convection, vastly increases our ability to understand the evolution of continental margins and interiors, in terms of uplift and subsidence, and the waxing and waning of inland seas.
The fundamental key for linking surface and deep Earth processes is in devising and testing alternative absolute plate motion reference frames. The profound difficulty is that even though we have good control on palaeo-latitudes of continents, palaeo-longitudes are ill-constrained. It has been suggested that large igneous provinces (LIPs) and kimberlites at the Earth’s surface of the past 300 Myr have mostly been sourced by deep plumes from the edges of the two large low-shear-wave velocity provinces (LLSVPs) overlying the core-mantle boundary in the African and Pacific hemispheres; these are referred to as the “Plume Generation Zones” (PGZs). However, whether the African and Pacific LLSVPs have remained in the same place through the amalgamation and dispersal of Pangaea is not known and subject to much debate.
3.1.4 Participants (including research students):
- Prof. Dietmar Müller (The University of Sydney)
- Prof. Sanzhong Li (Ocean University of China)
- Mr. Xianzhi Cao (Ocean University of China, PhD candidate)
- Dr. Nicolas Flament (The University of Sydney)
3.1.5 Relevant publications:
- Müller, R.D., Flament, N., Matthews, K.J., Williams, S.E., Gurnis, M., 2016. Formation of Australian continental margin highlands driven by plate–mantle interaction. Earth and Planetary Science Letters 441, 60-70.
- Flament, N., Gurnis, M., Müller, R.D., Bower, D.J., Husson, L., 2015. Influence of subduction history on South American topography. Earth and Planetary Science Letters 430, 9-18.
- Heine, C., Yeo, L.G., and Müller, R.D., 2015. Evaluating global paleoshoreline models for the Cretaceous and Cenozoic. Australian Journal of Earth Sciences 62, 275-287.
- Herold, N., Buzan, J.R., Seton, M., Goldner, A.P., Green, J.A., Huber, M., Markwick, P., Müller, R.D., 2014. A suite of early Eocene (~55 Ma) climate model boundary conditions. Geoscientific Model Development (GMD) 7, 2077–2090.