Paleomagnetic data on the Turonian-Santonian of the Southwestern Crimea: records of anomalous Geomagnetic Field regime in terminal Cretaceous Normal Polarity Superchron

Andrey Guzhikov1, Anastasiya Guzhikova1, Evgeny Baraboshkin2, Iliya Ryabov1

1Saratov state university
2Moscow state university


Anomalously large amplitude variations of the characteristic components of magnetization (ChRM) were recorded in the Turonian–Santonian interval of the southwestern Crimea. The postorientational genesis of them is substantiated, among other things, by the results of the fold test. Initially, an anomalously large scatter of ChRM was recorded in the Turonian, Coniacian, and Santonian deposits of the Aksu-Dere section. However, it could not be unambiguously associated with the peculiarities of the Late Cretaceous Geomagnetic Field regime due to the lack of data to substantiate the primacy of magnetization. The data from the Santonian interval of the Mt. Chuku section are of the key importance for elucidating the nature of high amplitude paleomagnetic variations. The variations in ChRM, like those in Aksu-Dere, are recorded in most of the Santonian of the Mt. Chuku section. The uppermost Santonian of the Chuku section, as well as uppermost Santonian of the Kudrino-2 section, are characterized by a high concentration of ChRM. If to convert the ChRM directions from the geographic coordinates into the stratigraphic one, we use the averaged occurrence elements of the layers, which are determined only by the tectonic inclination, then the fold test is positive. Therefore, the age of magnetization cannot be younger than the end of the diagenetic stage. The substantiation of the diagenetic (post-orientational) genesis of magnetization is identical to the proof of its primacy because the duration of diagenesis is short (the order of thousands to tens of thousands of years). The results of the fold test for the average directions for each Turonian–Santonian section of the SW Crimea also unambiguously indicate the pre-folding magnetization. Thus, the obtained data can be interpreted as a record of the anomalous behavior of the ancient Geomagnetic Field over several million years (at least), corresponding to the time interval from the base of Coniacian to the end of Santonian (~90 to 84 million years). The study was supported by the Russian Science Foundation Grant No. 22-17-00091, https://rscf.ru/project/22-17-00091/.