Speaker: Emily Stoll, PhD candidate, Dept. of Earth & Planetary Sciences, Harvard University

Title: Basins in a pre-plate tectonic world? A non-uniformitarian basin model and examination of the 3.4 Ga Strelley Pool Formation, Western Australia

Abstract: Plate tectonics significantly contribute to the long-term habitability of a planet, including through climate regulation, nutrient recycling, and niche development. However, Earth may not have had plate tectonics throughout its history, with many researchers proposing a non-uniformitarian geodynamic regime, partial convective overturn (PCO), instead. In PCO, dominantly vertical tectonism is driven by density instabilities between rising granitoid diapirs and sinking mafic and ultramafic volcanic material. Predicted effects of PCO on the rock record focus on structural, igneous, and metamorphic evidence, many of which are non-unique. To supplement this, we propose a qualitative model of PCO basin sedimentology, stratigraphy, and architecture based on characteristics of salt minibasins. We argue that halotectonics provide an appropriate analogue for PCO surface processes as both have density-driven diapirism resulting in surficial patterns of domal relief and inter-diapir accommodation. Our PCO basin model is characterized by the combination of (1) paleohighs over domes, (2) syn-depositional diapirism, and (3) diapir-influenced basin shape. We compare our model to the 3.4 Ga Strelley Pool Formation, a proposed type-example of a PCO basin based primarily on structural and igneous studies. We examine the provenance, stratigraphy, and sedimentology of the Strelley Pool Formation across six different greenstone belts within the East Pilbara Terrane, Western Australia to see if it has evidence supporting the three characteristics of a PCO basin. Preliminary results suggest that there is a more complex tectonic story than simple PCO diapirism.