Late Permian magnetostratigraphy on the eastern Russian platform

The Late Permian is characterized palaeomagnetically by the transition from the long-lasting Permo-Carboniferous reversed polarity superchron (PCRS; also called: Kiaman reversed superchron) to the subsequent Permo-Triassic mixed polarity superchron, often called Illawarra mixed polarity superchron. Many discussions have been devoted to the exact time of the onset of the Illawarra reversals. Apparently contradictory data have been obtained from magnetostratigraphic sediment successions formed in different environments in many regions of the world. These sediments have been dated using classical geological or palaeontological correlation methods without the possibility of absolute age control because volcanogenic materials are missing. Application of the local or regional stratigraphic schemes leads to difficulties and apparent diachronous age estimates of the end of the PCRS. This paper shows that in agreement with earlier investigations, the continental red beds of the Upper Permian Tatarian stage on the eastern Russian platform record the Kiaman/Illawarra boundary. The Illawarra reversal sequence measured in a type section at the Volga river can be correlated well with the corresponding polarity pattern found in the Tethyan realm if one assumes a longer duration of the Tatarian than previously suggested.     

C geochronological constraints for the volcanic history of the island of Ischia (Italy) over the last 5000 years

The chronology of the most significant eruptions at the island of Ischia in the last 5000 years has been studied by means of Accelerator Mass Spectrometry to obtain ¹⁴C data. The results are in good agreement with stratigraphical and archeological constraints. This allows interpretation of the measured dates as ages of the eruptions which produced the deposits overlying or incorporating the sampled paleosols and charcoal fragments, respectively. These ages define the timing of volcanism in the last 5000 years, suggesting that the recent volcanic activity at Ischia is characterized by periods of very intense volcanism alternating to periods of quiescence. This timing of the volcanism is correlated with the behaviour of the magmatic system and dynamics of resurgence of the Mt. Epomeo block.     

Magnetic stratigraphy of Vesuvius products. I. 1631 lavas

An extensive palaeomagnetic study has been undertaken to provide further elements leading to a better assessment of the volcanic history of the Vesuvius. This work refers to lavas for which the date of emplacement have recently been questioned; i.e. either during the period 968–1037 or in 1631. From 7 sites, 97 sun-orientated specimens have been collected. The dominant magnetic carrier for all sites consists of magnetite on the basis of an analysis of IRM acquisition. The linearity analysis carried out on at least 6 specimens per site subjected to PAFD has indicated the presence of single- and multi-component magnetizations. The within-site mean directions of 5 sites are close to each other suggesting that lavas from these sites can be ascribed to the same volcanic event. The remaining 2 sites can also be referred to this event on ground of stratigraphical considerations. The plotting of the between-site mean directions of the previously mentioned 5 sites on the Vesuvius secular variation curve suggests that the lavas from these sites could not be emplaced during the period 968–1037 but some hundred years later than 1301. The stratigraphic and historic dating of deposits and a building, respectively, at one of the 2 remaining sites allows to conclude that all the investigated flows had to be emplaced during the 1631 event. Therefore, this event was characterized not only by explosive activity but by an important effusive phase as well.