Magnetic stratigraphy of the Permian-Triassic traps in the Kotui River valley (Siberian Platform): New paleomagnetic data

Abstract

The Permian-Triassic effusive traps in the Kotui River valley (Siberian Platform) were studied in detail by a paleomagnetic method, resulting in a summarized magnetic stratigraphic section of the studied sequence. The presence of the reversed polarity zone corresponding to the Khardakh Formation was argued for the section basement. Inside the Kogotok Group, the boundary between the direct and reversed polarity zones occurs in the lower part of the Onkuchak Formation and mismatches the boundary between the formations of the Kogotok Group, as was accepted before. These results contradict the presence of the transition record between the direct and reversed polarity zones in basalts of the lower part of the Onkuhcak Formation. The strong transitional interval between the Ivakinsk Formation and the upper parts of the Nadezhda Formation of the Norilsk section has no analogs in the Kotui section. This means the absence of any significant volcanic activity in the Maimecha-Kotui province during the intense eruptions in the Norilsk region resulting in origination of the greater part of the lower formations of the trap sequence. These data and possible correlations of the traps of the Kotui River valley and Norilsk region indicate that the Norilsk and Maimecha-Kotui sections were temporally overlapped.