astrochronostratigraphic

Astrochronostratigraphy is a field in geology that combines astronomical theory with stratigraphy to build high-resolution, absolute time scales for sedimentary records. It uses the imprint of Earth's orbital variations on sediments to assign numerical ages to layers, extending dating capabilities beyond radiometric techniques. The approach sits at the intersection of cyclostratigraphy, astrochronology, and chronostratigraphy.

The method detects orbital-periodicities in sediment sequences using proxies such as lithological cycles, stable isotopes (δ18O, δ13C), magnetic susceptibility, or color changes. Time-series analyses (Fourier, wavelet) reveal cycles corresponding to the Milankovitch climate cycles: eccentricity (~100 kyr), obliquity (~41 kyr), and precession (~23 kyr). The observed pattern is then tuned to astronomical solutions to produce an astrochronology, often anchored by independent ages, magnetostratigraphy, or global event tie-ins. Robust results require relatively continuous sedimentation, careful handling of diagenesis, and consideration of possible hiatuses or variable sedimentation rates.

Applications include refining regional and global timescales, correlating stratigraphic sequences across basins, and constraining the durations of climate events and biological turnovers. Astrochronostratigraphy has been particularly influential in Cenozoic and Mesozoic records but is applicable to other intervals where clear orbital signals can be detected.

Limitations involve diagenetic alteration, hiatuses, reservoir effects, and potential bias from mis-tuning or weak independent anchors. Despite these challenges, astrochronostratigraphy provides a powerful framework for integrating astronomical forcing into geological time scales and for improving the precision of sedimentary chronologies.