Understanding rapid climate variations during the Late Ordovician in terms of astronomical forcing.

Cyclostratigraphy comprises the study of astronomically forced climate cycles as expressed in the sedimentary record. Such studies are particularly challenging when applied to the deep geological time. Recent studies (De Vleeschouwer & Parnell, 2014) however, have now successfully demonstrated the astronomical rhythm of climate changes as far as the middle Paleozoic. We are presenting a new research project that aims to develop an astrochronological framework for the Late Ordovician. We are investigating and selecting sections with the highest potential for our studies, i.e. complete stratigraphic sections across a range of paleoenvironmental and paleoclimatological settings. We are testing various proxies to detect multiple astronomical parameters. High-resolution data sets including a new stable isotope record from the Upper Ordovician paleotropical carbonates superbly exposed on the Anticosti Island in eastern Canada were examined for identifying shorter astronomical periods. Our preliminary analysis of the Anticosti data set suggests the presence of a strong astronomical signal. Our sampling resolution allows for detection of the precession and obliquity signals and their long-term modulations. This interpretation opens perspectives for the development of an improved temporal framework and enhanced climatic interpretations in the early Paleozoic.