Variation rates of carbon- and biota-related events in deep time: challenges and progress

The proposal of novel theoretical ideas in Earth history such as plate tectonics and Darwinian life evolution has led to great leaps forward in the disciplinary development of geosciences. The rapid development of Earth-systems science in modern days has allowed integration of interactions among the Earth spheres and comparison at a range of time scales, favoring the development of novel theories. Comparison of geological events at different time scales is of particular importance. In modern days, changes in the Earth system are occurring at an unprecedented rate, in particular, a rapid increase in atmospheric CO2 concentrations and declines in biodiversity. Although not comparable in amplitude with changes observed in deep time, modern changes clearly exceed them in the rate. This indicates that rates of variation in the carbon cycle and biodiversity in deep time are critical to understanding the trajectory of global changes in modern days and their consequences. However, it is a grand challenge to investigate rates of geological events in deep time due to generally low temporal resolution and unavailability of reliable proxies for some paleoclimatic and paleoenvironmental factors. Consequently, the causal relationships of life to environments in Earth history have been investigated mainly on the basis of the amplitudes of geological and biological events. To address this knowledge gap in rates of processes between the deep time and modern records, it is necessary and important to conduct multidisciplinary studies. It is notable that the rapid development of isotopic geochronological dating techniques has greatly enhanced precision dating of past events, and that big data analysis of paleontological records, high-resolution stratigraphic correlations, and astrochronological techniques have contributed to improvements in the dating resolution of ancient events by an order of magnitude or better, presently yielding dates with an accuracy to tens of thousands of years that can provide a robust high-resolution geochronological framework for geochemical, isotopic, and lipid biomarker studies. In addition to the dating issue, it is of significance to propose novel proxies for paleoenvironmental analysis and to develop numerical simulation techniques suitable for reconstruction of interactions among Earth-system spheres in deep-time systems. Large models with the aid of artificial intelligence are likely to become important tools for qualitative evaluation of causal relationships between the carbon cycle and biotic events on the basis of intrinsic rates of variation. Preliminary studies were conducted in recent years on rates of variation of geological events such as the Big Five mass extinctions of the Phanerozoic, but these investigations were conducted at low (ca. million-year) temporal resolutions that are incompatible with rates of modern changes. It will be essential to achieve temporal resolutions on the millennial scale in order to undertake accurate comparisons between ancient and modern changes in the global carbon cycle and biodiversity. The data gained through high-resolution studies of deep-time systems will enable us to bridge observational and theoretical gaps in knowledge between the modern and ancient Earth systems as well as to better achieve a more holistic understanding of interactions among its spheres, stimulating a transformative advance of interdisciplinary Earth-systems research.