Orbital Tuning of Short Reversed Geomagnetic Polarity Intervals in the Cretaceous Normal Polarity Superchron

Abstract

AbstractWhile the Cretaceous Normal Polarity Superchron has documented instances of brief reversed polarity intervals, the absence of accurate age determinations for such abrupt shifts poses a challenge in leveraging them as reliable reference tiepoints. This study presents a cyclostratigraphic analysis of gamma‐ray data from the DSDP Site 402A. The identification of Milankovitch cycles allowed us to construct a 405‐kyr astronomically‐tuned age model for two reversed events that occurred in the Aptian. Our results estimate an age of 117.03 ± 0.14 Ma for the Chron M”‐1r” or ISEA and 116.17 ± 0.14 Ma for reversal “2,” with timespans of ∼20 and ∼10 kyr, respectively. Sedimentation patterns are influenced by orbital eccentricity cycles with an average sedimentation rate of 5 cm/kyr. The short time intervals related to these reversals exposes the difficulty in their detection in cores through paleomagnetic analysis as well as in deep‐tow surveys.