140 The Proterozoic-Phanerozoic Transition: Laying the Foundation for the Modern Earth System

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
Mile High Ballroom 2AB/3AB

GEOLOGICAL RESEARCH THROUGH INTEGRATED NEOPROTEROZOIC DRILLING (GRIND): THE EDIACARAN-CAMBRIAN TRANSITION

Paper number: 140-10
Program: Technical Sessions
Time: 10:05 AM – 10:20 AM

Authors

Abstract

The Neoproterozoic Era (1000 - 541 Ma) is 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 outcrop-based studies has hindered developing quantitative models of Earth system functioning during that Era. The Geological Research through Integrated Neoproterozoic Drilling (GRIND) project begins to rectify this scientific shortcoming by obtaining 13 cores through the archetype successions that record this environmental and biogeochemical change.

The specific targets are the Ediacaran-Cambrian transition (ECT; c. 560-530 Ma) in south Namibia (Nama Group), strata of west Brazil (Corumbá Group), and South China (Doushantuo, Dengying and equivalent formations). Drilling in Namibia and Brazil is complete, and drilling in China will commence in 2023. The drill sites allow sampling of shallow-to-deeper marine rocks across shelf-to-basin transects. The work aims to 1) construct a highly resolved temporal framework that will lead to the development of age models for the ECT; 2) refine the patterns of biotic evolution of organic-walled and mineralised microfossils, metazoans and trace fossils, and identify the links between and test hypotheses about biological evolution and environmental change, and 3) using fresh, unweathered samples, determine the palaeoenvironmental and biogeochemical conditions that led to the rise of oxygen and distinguish cause-and-effect relationships and basin-specific versus global-scale secular trends in geochemical and stable isotope patterns.

We present sedimentological data from the characterised split cores from Namibia and Brazil, and proposed analyses by international research groups. Split cores are permanently archived at an in-country repository as well as the Federal Institute for Geosciences and Natural Resources in Germany. All cores will be available for future research, education and national capacity building activities and mark the first step towards creating an on-shore core archive that will match in stature that of the IODP.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-381418

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