Paleomagnetism of the Abinskaya Group of the Kuznetsk Depression (southern Siberia) – Implications for the Evolution of the Siberian Large Igneous Province at the Permian–Triassic Boundary

Abstract

—We report results of a systematic paleomagnetic study of the Abinskaya Group of the Kuznetsk depression, including a typical volcanic complex that reflects important features of the evolution of the Permian–Triassic Siberian large igneous province (LIP). Four zones of magnetic polarity have been established in the group’s deposits. We revise the correlation of the volcanic sheets of the Mal’tsevo Formation (Fm.) at the base of the group with the Ivakinsky Fm. of the Norilsk region, which is linked to the initiation of trap magmatism. The beginning of the eruption of the Saltymak complex volcanic rocks in the Kuznetsk area corresponds to the boundary between subchrons LT1n.1n and LT1n.1r (251.2 Ma) within the Kedrovka sub-formation of the Mal’tsevo Fm. This boundary was traced in the magnetostratigraphic sections of the Maimecha-Kotui, Koltogor-Urengoy, Western Taimyr, and Norilsk regions of the Siberian LIP and suggests a correlation of the Mal’tsevo Fm. volcanic rocks with the upper part of the undifferentiated interval of the Onkuchak – Tyvankit (?) fms., the base of the Korotchaev Fm., the Verkhnetam Fm. and the top of the Samoed Fm. The duration of this main pulse of volcanism in the Kuznetsk depression did not exceed 0.1 Myr. The volcanic sheets of the second, significantly weaker pulse of the Yamin Fm. are compared with the Maimecha Fm. of the Maimecha-Kotui area and the top of the Korotchaev Fm. of the Koltogor-Urengoy area. Thus, the accumulation of the entire Abinskaya Group, including the sedimentary complex of the Sosnovka Fm., lasted no more than 1.5 Myr. Except for the initial stage, this coincided with the eruption of most of the Maimecha-Kotui and Koltogor-Urengoy trap sections. The early magmatism of the Ivakinsky time and its analogs in other areas of the Siberian province during the Permian–Triassic boundary in the Kuznetsk depression probably corresponds to the break between the Taylugan Fm. and the Abinskaya Group. The mean paleomagnetic pole (PLat = 59.0°, PLon = 160.3°, A95 = 5.7°, N = 33) calculated for the entire studied section reflects the paleogeography of the Kuznetsk depression and can be considered a reference pole for the Permian–Triassic boundary.