A Late Cretaceous true polar wander oscillation

Area of Science:

• Paleomagnetism
• Geophysics
• Earth Sciences

Background:

• True polar wander (TPW), or planetary reorientation, is a known phenomenon on other celestial bodies and Earth today.
• Evidence for past TPW on Earth is challenging to interpret due to concurrent plate tectonic movements.
• The existence of Late Cretaceous TPW around 84 million years ago (Ma) is debated, with some paleomagnetic data suggesting stability.

Purpose of the Study:

• To investigate the prevalence of true polar wander in Earth's past, specifically during the Late Cretaceous period.
• To re-evaluate existing paleomagnetic data and present new findings to resolve the debate on Late Cretaceous TPW.

Main Methods:

• Acquisition of a new, high-resolution paleomagnetic record from two overlapping stratigraphic sections in Italy.
• Analysis of paleomagnetic data to reconstruct past changes in Earth's spin axis orientation.

Main Results:

• The study presents evidence for a significant true polar wander oscillation of approximately 12° between 86 and 78 Ma.
• This oscillation represents the most recent large-scale TPW event documented in Earth's geological record.
• The findings challenge the long-held assumption of a stable spin axis over the last 100 million years.

Conclusions:

• The new paleomagnetic data strongly support the occurrence of true polar wander during the Late Cretaceous.
• This discovery necessitates a revision of our understanding of Earth's rotational stability over geological timescales.
• The findings have implications for interpreting past climate and paleogeographic reconstructions.