Project 597 - Amalgamation and breakup Pangaea: The Type Example of the Supercontinent Cycle
There is widespread acceptance that between 300 and 200 million years ago, all of the Earth’s continental land masses were assembled into a giant supercontinent, Pangæa, surrounded by a superocean, Panthalassa. However, different configurations have been proposed, e.g. Pangæa A and B. The breakup of Pangæa over the last 200 million years resulted in the formation of new oceans (such as the Atlantic, Indian and Southern) between the dispersing continental fragments. For the past 25 years, however, evidence has been amassing that Pangæa was only the latest in a series of supercontinents that assembled and dispersed over the last 2.5 billion years. Although the mechanisms responsible are controversial, many geoscientists agree that repeated cycles of supercontinent amalgamation and dispersal have not just taken place, but have had a profound effect on the evolution of the Earth’s crust, atmosphere, climate, and life.
The focus of the proposed research is to understand the mechanisms that led to the formation of the latest supercontinent, Pangæa, and in so doing provide a template by which the origin of the older supercontinents can be evaluated. Although we know to a first-order where and when Pangæa formed, we do not know the locations and precise timing of assembly of the constituent pieces, and how or why Pangæa formed. The tectonic processes involved resulted in the creation and destruction of oceanic lithosphere, mountains, and by implication the mineral endowments that accompanied them. We will focus on the evolution of two types of Palaeozoic oceans whose contrasting fates were pivotal in the development of Pangæa; (a) interior oceans, such as the Rheic and Iapetus oceans which were located between converging continents and were consumed to produce Pangæa, and (b) exterior oceans which surrounded the continents during the entire Paleozoic, and became one superocean (Panthalassa) when Pangæa formed. Interior oceanic lithosphere originated between 600 and 500 million years ago and its closure produced a series of orogenic events culminating about 300 million years ago with terminal collision between Laurentia (North America), Baltica (western Europe) and Gondwana (South America-Africa), arguably the principal collisional event in the assembly of Pangæa. The evolution of the exterior ocean is primarily preserved in the 18,000 km long Terra Australis orogen, which was located along the periphery of Pangæa and records sem-continuous subduction between 570 Ma and 230 Ma.
The geology that records the evolution of these ancient oceans was widely dispersed by the breakup of Pangæa, and is now widely distributed. There are major uncertainties in the identification of the ancient margins of these oceans, the mechanisms and timing of initial rifting and opening, and the geodynamics of their closure. Key areas have been identified for field workshops and conferences that shed light on the origin of Pangæa.
By definition, any study of Pangæa is global in scope. Many countries and every continent have pieces of the puzzle and only by bringing geoscientists together from many nations can we obtain a comprehensive understanding of its origin. Our project will bring together scientists from at least thirty countries, from different geological disciplines with expertise in different regions, and from academia, government, and industry, with the goal of understanding the processes that resulted in the amalgamation of Pangæa will provide natural constraints for future geodynamic models of supercontinents.