Anomalous magnetization of the Permian-Triassic Nedubrovo red beds, Moscow basin

Abstract

A Nedubrovo member was recently described by (Lozovsky et al., 2001) and is the subject of continuing disputes due to the uncertainty of its age. Numerous determinations of fauna and flora allow to suggest the age of the Nedubrovo deposits as Upper Permian (Arefiev et al., 2016, Lozovsky et al., 2016) or Lower Triassic (Lozovsky et al., 2017). The uniqueness of the Nedubrovo member is also determined by the absence of its stratigraphic analogues within the Moscow sedimentary basin. Here we present the results of complex paleomagnetic and rock magnetic studies of the oldest Nedubrovo horizons of the Lower Triassic of the Moscow basin, which are outcropped in the lower stream of the Kichmenga River and lie on the clays of the Vyatkian stage of the Upper Permian. We found the paleomagnetic direction of the characteristic component of the magnetization of the studied red beds to be anomalous (slat = 60.04521°, slong = 45.74047°, N = 142, D = 246.3°, I = –6.6°, K = 10.0, α95 = 3.9°) and, with a high degree of probability, it corresponds to the period of significant and prolonged deviation of the Earth’s magnetic field configuration from the Geocentric Axial Dipole (GAD). The presence of anomalous paleomagnetic directions in Late Permian sedimentary and volcanic sections within Eurasia can be used as a powerful tool for local and regional magnetostratigraphic correlations, and it also indirectly suggests the Late Permian age of the Nedubrovo sediments.