Magnetic Reversals During the Deccan Volcanism: Paleomagnetic Insights From the Pachmarhi Dykes

Abstract The three main dyke swarms that are linked to the Deccan Continental Flood Basalts are the Nasik‐Pune, Western Coastal, and Narmada‐Satpura‐Tapi (N‐S‐T) swarms. Encompassing approximately 244 mapped basaltic dykes, mainly trending E‐W and positioned along an ancient tectonic zone, the Pachmarhi dyke swarm is situated in the eastern N‐S‐T segment. The length of these dykes varies from 140 m to 22 km, with a mean abundance between 5 and 15 km. According to petrographic and rock magnetic analyses, the main magnetic remanence carriers are high‐ and low‐titanium magnetite particles, primarily in the pseudo‐single domain state. Paleomagnetic analyses of 14 dykes show that two of them exhibit both polarities within the same dyke, seven have reverse polarity, and five have normal polarity. This implies periodic intrusion of magma during geomagnetic reversals. The mean ChRM directions for normal and reverse polarity dykes are D m = 329.3°, I m = −40.3° ( k = 80.1, α 95 = 8.6°, n = 31) and D m = 154.4°, I m = 39.5° ( k = 122, α 95 = 5.5°, n = 69), respectively. The combined mean ChRM direction ( D m ≈ 332°, I m ≈ −39.8°) yields a paleopole at 37°N, 68.6°W, closely aligning with the Nandurbar‐Dhule (N‐D) dykes and the Deccan Superpole. The results indicate that the Pachmarhi dykes were formed during a mostly synchronous magmatic episode along the Narmada–Son Lineament. Due to the lack of direct geochronological constraints for these dykes, their precise correlation with the eruptive history of the Deccan Traps remains unresolved.