Variation on a 36-Ma-old theme: length, intensity and rhythm of volcanism. A record from the Hocheifel (Germany)
Abstract K-Ar eruption ages of Tertiary alkali-basalt occurrences in the Hocheifel form the basis of a frequency distribution, whose significance and geological meaning are discussed. Volcanic activity in the area occurred between 45 Ma and 24 Ma, reaching a maximum at 36.0 Ma. The curve of volcanic intensity is periodically modulated, with a period of 4.1 ± 0.5 Ma. This rhythm appears simultaneously in all the volcanic rock types, making a correlation between rock chemistry and age impossible. Volcanism is considered to have been stationary throughout the entire eruptive period, as the geographic centres of all eruptive phases coincide.