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

While 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 similar to 20 and similar to 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. The Cretaceous Normal Polarity Superchron (CNPS) was characterized as a "quiet zone," which includes no geomagnetic reversals during similar to 38 Myr. A number of studies propose significant fluctuations in geomagnetic intensity, with distinct features observed in paleosecular variations, including periods of reversal events, and the actual occurrence, timespan and ages for these rapid magnetozones have been under debate in literature. This paper provides the age and constrains the timespan of two of these debated reversals (i.e., M"-1r" or ISEA, and "2") during the CNPS. The determination of the age of the reversals during the CNPS is a fundamental support for global correlations. Orbital tuning for M-1r (ISEA) has an age of 117.03 +/- 0.14 Ma and a timespan of 20 kyr The reversal "2" has an age of 116.16 +/- 0.14 Ma and a minimum timespan of 10 kyr DSDP Site 402A has an average 5 cm/kyr sedimentation rate and eccentricity Milankovitch cycles rules sedimentation patterns