Over the past decade, SCAR Action and Expert groups (e.g. ADMAP, CGG) have demonstrated that the architecture of the Antarctic continental crust is much more complex than previously recognised. Crustal heterogeneity is superimposed on large scale mantle variability, and this contributes towards determining the heterogeneity in Geothermal Heat Flow in Antarctica. Antarctic Geothermal Heat Flow variations are particularly ill-constrained, especially at regional scale, but are critically important as they affect basal ice melting patterns and ice-sheet dynamics. The geodynamic evolution of Antarctica over time is also still ill-understood but hotly debated. West Antarctica, for example, was the site of long-lived subduction of Paleo-Pacific oceanic lithosphere but today the margins of Antarctica are predominantly composed of various types of passive continental margins. The interior of the continent in both West and East Antarctica appears to be criss-crossed by major continental rift systems. In West Antarctica, the West Antarctic Rift System provides the key lithospheric cradle for the rapidly changing West Antarctic Ice Sheet. And enigmatic subglacial basins in East Antarctica host the largest and notably most vulnerable marine-based portions of the huge East Antarctic Ice Sheet. All these tectonic features have been modified via interaction and superposition of fluvial and glacial erosion and associated isostatic responses, as well as dynamic (i.e. deep-seated mantle related) topography, and collectively these processes have imparted key controls on the evolution of Antarctica’s subglacial bed topography and bathymetry. Topography and bathymetry are two critical basal boundary conditions that affect past, present and future ice sheet dynamics and ice sheet-ocean interactions respectively.
The AGE PPG aims to combine, make more widely known and more openly accessible geological and geophysical data, also to the global geoscience community, and to develop better integrated interpretations from disparate geological, geochronological, geochemical, and geophysical datasets to help fill the current major knowledge gaps in Antarctica. AGE aims to work synergically with the BEDMAP and RINGS glaciological communities to foster the acquisition of new radar data and hence improve current realisations of bed topography and bathymetry. AGE intends to help launch and promote new ambitious geoscience projects both during the preparatory phases and ultimately during the 5th International Polar Year 2032/33.
We propose three pillars and task groups for AGE:
1. Architecture
Task group 1 will integrate, analyse and exploit more fully, also by using novel approaches, the wealth of data made available from previous and ongoing SCAR Action and Expert groups (e.g. ADMAP, CGG, GEOMAP, ANTVOLC). We aim to obtain a more comprehensive 4D picture of the Antarctic continental lithosphere, including its Archean nuclei, orogenic belts, sedimentary basins and its active and passive continental margins. The project planning group already includes a wide range of geophysicists with expertise in both imaging and modelling the crust and mantle, which will work synergically with our geological teams. This pillar will address key questions such as:
- What types of plate and continental margins does Antarctica incorporate; how have they evolved and what is their significance for the opening and evolution of ocean gateways?
- What is the distribution and architecture of crustal provinces from the oldest Archean cores to the youngest active and passive plate margins?
- What is the distribution and significance of on- and oN-shore sedimentary basins and what do they reveal about the evolution of the Antarctic lithosphere itself?
- What is the structure of the underlying mantle lithosphere; how has it evolved and how can its present heterogeneity be best explained?
- How do lithosphere and structural heterogeneities affect present and past topographic variability?
2. Processes
Task group 2 will focus on the processes governing the formation, destruction and preservation of the continental crust, the balance among these processes and the significance of the continental crust for radiogenic heat production in Antarctica.
Orogenic processes: Antarctica hosts several Archean continental blocks, the significance of which needs to be better constrained in the context of early Earth evolution. Our knowledge of Antarctic orogenic belts, particularly of Precambrian ones, is fragmentary at best. However, the styles of different orogenies, whether large or small and whether collisional or accretionary, play a key role for the distribution of radiogenic heat-producing elements. Fragments of Grenville-age orogenic belts have been described as either accretionary or collisional, and the same applies for different Late Neoproterozoic orogenic belts. If accretionary, did these orogens form in predominantly advancing or retreating settings and how long were these active? Long-lasting orogenies can concentrate heat-producing elements in their orogenic cores and can ultimately lead to hot orogens. Such orogens can also collapse leading to thinner lithosphere.
Erosion and basin formation: sedimentary basins can provide key information both about the underlying and the surrounding crust, e.g. via the age and provenance of the sediments. Antarctica has many large sedimentary basins, which need to be more fully understood in terms of their architecture and the processes responsible for their formation and evolution.
Crustal growth and destruction: Antarctica hosts many different plate margins, a major former long lived active plate margin in West Antarctica, and several different passive continental margins. The rift margin along the Indian sector is a particularly high-standing rift margin that reactivated the Late-Neoproterozoic East African-Antarctic Orogen. In contrast, the Australian sector was mostly a low-relief margin from the Oligocene onwards and this was likely conducive to a much more dynamic East Antarctic Ice Sheet in this sector. However, what caused the different margin styles in the first place remains to be investigated further.
Continental Rifting: Antarctica is dissected by numerous major rift systems and the tectonic and magmatic processes that affected them over time also needs to be researched further.
The nature of the lithospheric mantle is also poorly constrained, but volcanic rocks can be an excellent source of new information for research, particularly if coupled with more refined seismological observations and modelling.
The project planning group will involve multidisciplinary expertise, which will address investigations from field observations, geophysics and remote sensing to modelling.
Some of the key questions in this pillar are:
- What are the key geological processes that occurred from the oldest Archean cores to the youngest active and passive plate margins in Antarctica?
- How did major interior sedimentary basins form and evolve?
- What do volcanic rocks tell us about how Antarctica’s mantle evolved?
- How do spatially and temporally variable exhumation, glacial erosion and uplift rates relate to both surface processes and deeper crustal and mantle heterogeneities?
- What governs the different styles of continental rifting, passive margin formation and break up evolution both within and around Antarctica?
3. Interactions
Task group 3 will deal with the different kinds and levels of Antarctic interactions such as: the role of the Antarctic continent in plate tectonic evolution including the global supercontinent cycle; lithosphere, cryosphere, ocean and biosphere interactions through geological timescales, including water and CO2 exchange with the atmosphere and the cryosphere. The significance of Antarctica’s Archean cores including their interactions with early Earth and life aligns with ongoing projects of some members of the AGE planning group. Antarctica’s role in the global weathering cycle and impact on earlier glaciations, both in Snowball Earth and during Gondwana glaciation are important. Antarctica’s various orogens were accompanied by significant topographic changes: some of them likely exceeded todays Himalaya in size and extent and therefore were likely climatic game changers over time. Antarctica’s influence on the evolution of the biosphere is also a tantalising area for further multidisciplinary research.
Some of the key questions to be addressed are:
- What role did Antarctica play in the supercontinental cycle; how can its former neighbours inform us better on Antarctica’s cryptic composition, structure and processes?
- What role did the different parts of Antarctica play in the evolution of the Neoproterozoic plate tectonic puzzle and Snowball Earth?
- What influence did Antarctica’s different continental margins have for the evolution of ocean gateways, global currents and atmospheric evolution, and how do these different interactions influence the Antarctic biosphere?
- What role have interactions between surface processes and mantle and crustal heterogeneities played for Antarctica’s topography evolution, geothermal heat flow heterogeneity and ice-sheet dynamics and stability?
- What effects does subglacial geology have on sub-ice hydrology, including lake infill and drainage processes and subglacial network and groundwater flow processes?
