Paleomagnetism and rock magnetism of early Cretaceous Rajmahal basalts, NE India: Implications for paleogeography of the Indian subcontinent and migration of the Kerguelen hotspot

Studies have been carried out on Rajmahal Traps (RT), India to define rock magnetic properties and also to derive a paleomagnetic pole position to understand the paleogeography and the position of the Kerguelen hotspot during early Cretaceous time. The results comprised of 90 oriented block samples from 18 sites. Detailed rock magnetic studies indicate Single Domain (SD) magnetite [Fe3O4] is the dominant magnetic carrier with ilmenite, pyrrhotite, and maghemite in the accessory form. The calculated Characteristic Remanent Magnetization (ChRM) directions yield a mean declination of 317.51°; mean inclination of −61.92° (α95 = 3.6°; k = 93.39). The derived mean Virtual Geomagnetic Pole (VGP) position of the RT at ~117 Ma is 11.37°N, 297.58°E (62.42°W) with A95 = 3.5°, k = 99.99 (dp = 4.33, dm = 5.58), agrees well with the synthetic APWP of India. The calculated paleolatitude (43.1°S) suggest a mid-latitude southern hemispheric location for the Indian subcontinent at the time of formation of the Rajmahal Traps. This paleomagnetic pole of RT basalts has minimal effect of secular variation and comply with the Geocentric Axial Dipole (GAD) model. The postulation of migration of mantle plume and the global mantle circulations are tested, and the present study results are in accord with this, suggesting the southward migration of the Kerguelen hotspot (mantle plume) by at least 6°.

Figure (a) The paleogeographic position of the Indian subcontinent at ~ 117 Ma (Early Cretaceous) determined from the present study. (b) The mean paleomagnetic pole data of the Rajmahal Traps plotted along the synthetic APWP for India based on the GAPWaP model by Torsvik et al. (2012).



M R Kapawar, M Venkateshwarlu* (2020). Paleomagnetism and Rock magnetism of Early Cretaceous Rajmahal Traps Basalts, India: Implications to a paleogeographic position of Indian subcontinent and Migration of Mantle Plume. Journal of Asian Earth Sciences, 201 104517, external link.