Project Report: Grinding Through the Ediacaran-Cambrian Transition.

The Neoproterozoic Era (1000 - 541 Ma) was one of the most dramatic in Earth history: metazoans evolved, the supercontinent Rodinia formed and broke apart, the global carbon cycle underwent high-amplitude fluctuations, oxygen concentrations rose and climate experienced at least two episodes of worldwide glaciation. However, the discontinuous and fragmented nature of outcropbased studies has hindered developing quantitative models of Earth system functioning during that Era. The Geological Research through Integrated Neoproterozoic Drilling (GRIND) project will begin to rectify this scientific shortcoming by obtaining 13 cores, each between 150 to 600 m in length, through the archetype successions that record the environmental and biogeochemical context during which animals evolved. The specific targets are the Ediacaran-Cambrian transition (ECT; c. 560-530 Ma) strata of west Brazil (Corumbá Group), south China (Doushantuo, Dengying and equivalent formations) and south Namibia (Nama Group). Our objective is to create a core network of correlative ECT strata that will enable the construction of a high resolution, temporally constrained geobiological, stratigraphic and geochemical database, as well as to provide a legacy archive for future research. The goal is to understand the drivers of the Neoproterozoic Earth system revolution: it began with simple eukaryotes that populated Earth during the preceding billion years of the Mesoproterozoic, underwent multiple Snowball Earth events and emerged with the oxygenated, diverse ecosystems of the Cambrian. The excellent outcrops of the Nama Group in Namibia are central to the success of the GRIND project, as is the invaluable expertise and support of the Geological Survey of Namibia. The stratigraphy of these rocks is well-documented and is an archetype of the late Ediacaran to early Cambrian. Furthermore, the presence of abundant ash beds offers excellent opportunities for obtaining high-precision U-Pb geochronology, making the Nama Group an ideal target for acquiring precise temporally constrained and detailed geobiological and geochemical data to meet our research goals. [ABSTRACT FROM AUTHOR]