Abstract
Astronomical insolation forcing is well established as the underlying metronome of Quaternary ice ages and Cenozoic climate changes. Yet its imprint on earlier eras (Mesozoic, Palaeozoic, and Precambrian) remains less well understood. In this seminar, we will explore how cyclostratigraphy can be used to distinguish climate modes in the pre-Cenozoic and to illuminate how Earth’s climate responded to astronomical forcing across geological time.
Because uncertainties on astronomical solutions (precession, obliquity, eccentricity) increase further back in time, pre-Cenozoic astronomical solutions cannot be applied as direct tuning targets. The Milankovic parameters can, however, serve as reliable metronomes for identifying the pacing of distinct climate states. These states were often more extreme than in the Cenozoic: global average temperature differences ranged from 5–32 °C, compared with 14–27 °C over the last 66 million years. Combined with an evolving biosphere and shifting plate tectonics, such extremes gave rise to distinctive Earth-system responses to orbital pacing. For example, the late Palaeozoic icehouse shows a pronounced eccentricity signal, linked to nonlinear cryosphere and carbon-cycle dynamics. By contrast, the Devonian warmhouse and the Late Cretaceous hothouse were marked by recurring episodes of marine anoxia, which may also have been paced by orbital rhythms.
Formally defining 405,000-year eccentricity cycles as chronostratigraphic units (astrochronozones) throughout the Phanerozoic would establish a common framework for comparing these responses and tracing the role of astronomical forcing across deep time. Moreover, Paleozoic and Precambrian cyclostratigraphy does not only shed light on Earth’s climate history: it also provides essential empirical constraints on Solar System dynamics, feeding back to refine astronomical solutions themselves.