EARTHTIME: A COMMUNITY-BASED EFFORT TOWARDS HIGH-PRECISION CALIBRATION OF EARTH HISTORY

Many fundamental problems in the geosciences rely on precise and accurate knowledge of geological time. For example, in paleontology information on the rates of origination vs. extinction of fossil taxa is essential to understanding what drives biological evolution and the precise timings of major extinctions is crucial for pinpointing probable causes. Interactions and/or interdependence among Earth's major biogeochemical cycles can only be examined through space-time correlations of multiple extended, uninterrupted, and high-resolution geochemical time series. Similarly, Earth's paleoclimatic conditions can be effectively evaluated only with a common geological timescale to quantify synchrony, lags and leads among climate proxy records. In each case geological time is customarily treated as the "independent variable"; deductions and conclusions are made assuming that the geological timescale as given is basically precise and accurate. The time has come to reframe these research areas with a new geological timescale with significantly improved accuracy and precision standards commensurate with new and emerging geochronologic and chronostratigraphic methodologies. Current geological timescales are based on data of highly variable quality. Most, if not all of these compilations are tied to paleontologically defined boundaries. Furthermore, many timescales have averaged dates obtained by different techniques, with differing (though largely ignored) absolute uncertainties. Inconsistent calibrations between different geochronometers are increasingly evident and must be reconciled before a seamless timescale can be contemplated. The result, which is propagated into subsequent publications, is a timescale that is often poorly calibrated in absolute terms. Consequently, the greatest uncertainty in most analyses of geologic and evolutionary rates is the timescale itself. To address these problems EARTHTIME is proposed as a new community-based effort to focus attention on the calibration of at least the last 800 million years of earth history using a unified, multi-chronometer approach. This in turn will allow earth scientists to address a whole new series of questions that rely on knowledge of precise rates of biological, geological, and climatic change.