Plate reconstruction studies show that the Neotethys Ocean was closing due to convergence of Africa and Eurasia towards the end of the Cretaceous. The period around 75 Ma reflects the onset of continental collision between the two plates, although convergence was still mainly accommodated by subduction, with the Neotethys slab subducting beneath Eurasia. Africa was separated from the rapidly north moving Indian plate by the Owen oceanic transform in the northeast. The rest of the plate was surrounded by mid-ocean ridges. Geologic observations in large basins show that Africa was experiencing continent-wide rifting related to northeast-southwest extension. We aim to quantify the forces and related paleostresses associated with this tectonic setting. To constrain these forces, we use the latest plate kinematic reconstructions, while balancing horizontal gravitational stresses, plate boundary forces and the plate's interaction with the underlying mantle. The contribution of dynamic topography to horizontal gravitational stresses is based on recent mantle convection studies. We model intraplate stresses and compare them with the strain observations. We find that slab pull, horizontal gravitational stresses and transform shear tractions in general acted with the same orientation as the absolute motion of the African plate 75 Ma. Both the balance between these three and the other, resistive, forces, and the fit to strain observations require the net slab pull, as experienced by the plate, to be low, pointing to the absence of a mature continuous Neotethys subduction zone at the time. This corresponds well to reconstructions of micro-continents interfering with the Neotethyan subduction.

Matthew Kemp

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Stories are an essential part of our everyday life, vehicles to understand how the world around us works, both physically and emotionally. They allow us to organise otherwise random facts and events into a cohesive and logical structure, making them easier to understand and remember. Science itself is also full of facts and processes, often seemingly disconnected but that, when put in context, pave the road for scientific discoveries. We propose that classical story-telling strategies can also be used to communicate science to a variety of audiences, specialist and non-specialist alike, and present a few practical examples of how this can be achieved. We focus on what we call the “story circle” narrative structure (see Fig. 1), a distillation of the “Hero’s Journey”(Campbell, 1949; Harmon, 2009). In this storytelling framework, the circle begins with a hero who, posed with a question, chooses to venture beyond their familiar space in a quest for answers. When the hero returns to familiar territory, they have been forever changed by their journey. Firstly, we discuss how this story circle can be directly mapped onto the structure of a research paper, enabling researchers to write up their work in a way that makes it easier to follow for the reader. Then we apply the story circle strategy to a real research example aimed at explaining large-scale mantle convection, in a story where silica is the “hero” who descends into the deep in a subducting slab to then rise back up to the surface in an upwelling plume. This approach to communicating science by exploiting its story-like qualities is key when explaining complex deep Earth processes to the non-academic public who, understandably, can struggle to grasp these concepts due to their abstract nature and detachment from everyday life. Ultimately, the scientific process is an expression of the most fundamental story of humanity – researchers look at the world as it is, see questions that need answering and go on a voyage of discovery to find the answers. When they return, the world has changed because of what was found on that journey. And so the cycle repeats, the circle keeps turning, and the ideas keep changing after every iteration. In science, however, we will never truly write “The End”.