地质学
极性(国际关系)
米兰科维奇循环
古地磁
白垩纪
地球磁场
古生物学
地磁反转
磁性地层学
地球物理学
化学
物理
磁场
冰期
生物化学
量子力学
细胞
作者
João Mauricio Figueiredo Ramos,Jairo F. Savian,Daniel R. Franco,Milene Freitas Figueiredo,Carolina Gonçalves Leandro,Fabrizio Frontalini
摘要
Abstract 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 ∼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.
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