Paleomagnetism and provenance of the lower Cambrian sedimentary rocks of the Udzha Uplift (north of the Siberian platform)

Abstract

Lately, data have been increasingly indicating an unusual, abnormal state of the magnetic field at the boundary of the Precambrian and Phanerozoic. This fact significantly limits the possibility of employing the paleomagnetic approach for creating various paleoreconstructions in this time interval, and it allows a better understanding of the evolution of the Earth’s magnetic field. Until recently, there was no exact binding of Lower Cambrian sections bearing an anomalous paleomagnetic record to the chronostratigraphical chart, which made it impossible to obtain adequate estimates of the duration of the anomalous state of the magnetic field. In this study we present the results of a paleomagnetic study of the Lower Cambrian terrigenous-carbonate rocks of the Udzha and Anabar Uplifts (Emyaksa and Medvezh Formations). New evidence has been obtained of the anomalous paleomagnetic record in these rocks, which manifests itself in the objective existence of two significantly different directions of the high-temperature magnetization components, the formation of which cannot be explained by a later remagnetization. U-Pb dating of detrital zircons constrains the maximum depositional age of the Manykay and Emyaksa Formations to ~520 Ma, which, in combination with the faunistic characteristic of the upper part of the Emyaksa Formation, points to the Atdaban age of studied successions. The age constraints obtained indicate a specific paleomagnetic record, and due to the peculiarities of the generation of the geomagnetic field of the terminal Precambrian–Early Cambrian Period, trace the paleomagnetic record back to the Atdaban age, inclusive.