Astrochronology

Astrochronology is the science of dating and correlating sedimentary, ice, and volcanic records by interpreting the imprint of astronomical cycles on Earth’s climate and sedimentation. It relies on regular variations in insolation driven by Earth's orbital parameters and axial precession, obliquity, and eccentricity (Milankovitch cycles) to create time scales within geological records.

The core methods include identifying cyclical patterns in climate proxies (oxygen isotopes, pollen, illite crystallinity), applying spectral analysis and cross-wavelet methods to detect orbital frequencies, and tuning records to an astronomical target solution such as the Laskar Milankovitch solutions (La2010, La2004). Once tuned, the resulting astrochronology provides numerical ages that anchor sedimentary sequences and paleoclimate reconstructions.

Applications: dating and correlating marine, lacustrine, and ice-core records; constructing high-resolution time scales; testing climate models; linking regional records to global orbital forcing. Limitations: non-unique tunings, gaps and diagenetic alteration in records, changes in sedimentation rate, regional climate signals that do not track insolation directly, and uncertainties in orbital solutions for deep time.

Astrochronology sits at the intersection of geology, climatology, and astronomy, complementing radiometric dating and magnetostratigraphy, and is essential for understanding the pacing of past climate events and the calibration of geologic time scales.