Geomagnetic Secular Variations at the Permian-Triassic Boundary and Pulsed Magmatism During Eruption of the Siberian Traps

The tempo of Large Igneous Province emplacement is crucial to determining the environmental consequences of magmatism on the Earth. Based on detailed flow-by-flow paleomagnetic data from the most representative Permian-Triassic Siberian Traps lava stratigraphy of the northern Siberian platform, we present new constraints on the rate and duration of the volcanic activity in the Norilsk and Maymecha-Kotuy regions. Our data indicate that volcanic activity there occurred during a limited number of short volcanic pulses, each consisting of multiple individual eruptions, and that the total duration of discrete eruption pulses did not exceed ~10,000 years (hiatuses are not included). Our study confirms the occurrence of a thick interval in the lower part of the Norilsk lava sections, which contains a record of geomagnetic reversal and excursion. Based on combined evidence from paleomagnetic secular variation and typical timescales for such reversals, we conclude that the ~1-km-thick lava stratigraphy, corresponding to ~20,000 km ³ of basalt, of the Kharaelakh, Norilsk, and Imangda troughs was formed during a brief, but voluminous, eruptive period of several thousand years or less. Our data further suggest that the ore-bearing Norilsk-type intrusions are coeval or nearly coeval with the boundary between the Morongovsky and Mokulaevsky formations. We calculated a new Siberian Permian-Triassic paleomagnetic pole Norilsk-Maymecha-Kotuy (NMK): PLat = 52.9°, PLong = 147.1°, A95 = 4.3°, K = 23.2, and N = 49 lava flows. It is shown that geomagnetic field variations circa 252 Ma were similar to those observed in the latest Cenozoic.