Comparison of Tectonic Phases and Geomagnetic Reversals in the Late Mesozoic and in the Cenozoic

Abstract

The authors consider the chronological relation of two groups of phenomena in the history of the Earth over the last 150 mln years. One of them is relatively short (a few million years) tectonic phases, or orogenic phases, identified by H.W. Stille in 1924 and characterized by an increase in compressive deformation in mobile belts of the Earth. Deformations that occur during such phases are quite explicable by collisional interactions of lithospheric plates. However, these interactions do not explain the synchronous occurrence of phases in different belts and on different continents. The other group is the frequency of magnetic reversals, i.e., changes such that the positions of magnetic north and magnetic south are interchanged. Tectonic phases are more frequent in epochs of frequent geomagnetic reversals. During the last 24 mln years, when geomagnetic reversals were especially numerous, tectonic phases came one after another in short intervals. An emerging trend for them is the lagging of phase peaks by one to two million years relative to the most frequent magnetic reversals. The chronological relations identified show that tectonic phases are determined not only by geodynamic processes in the lithosphere but also by the action of energy pulses that occur in the Earth's core and at the boundary of the core with the mantle, where the Earth's magnetic field is generated. On the geological time scale, this interaction takes place quickly, which excludes energy pulse convection and prompts the search for other mechanisms of this transfer. It is possible that it takes place because the lithosphere is affected by alternating body forces that occur under a change in currents in the core, which is followed by changes in the mode of the Earth's rotation and the adaptation to it of lithospheric masses.

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