Intracratonic stability: A comparison of paleomagnetic data from the north and the south of Dharwar Craton, India

Abstract

The prominent bend of Dharwar craton, India was recently suggested to post-date the ‘stabilization’ phase of the craton via a ~30°, anticlockwise, vertical-axis intracratonic rotation. The prima facie evidence for this rotation was the realignment of dyke trends following correction of the inferred deformation. The proposal also appeared to be consistent with the observed structural grain in the host Archean basement. We argue that using the trend of dyke swarms is not the ideal method to assess intracratonic rotation and instead we use variations in paleomagnetically determined declination data from these dykes. We find that multiple early Paleoproterozoic dyke swarms (the 2367, 2216, and 2082 Ma generations) preserve a systematic offset with a large uncertainty. The mean paleomagnetically permissible anticlockwise rotation is 19° ± 17°. Dykes emplaced during the ~1888 Ma LIP do not show the same offset, which suggests that rotation occurred prior to this time. Therefore, the 2082-1888 Ma interval brackets the window for any deformation and tectonism required to bend the Dharwar craton by about ~20°. No large-scale deformational events are documented in the Dharwar craton during this critical interval apart from the earliest stages of Cuddapah basin formation. We argue that the ‘observed’ rotation results from biases associated with how trends of dykes and their magnetic directions are compiled when age data are limited. The curvature of geological features in Dharwar craton is likely the tectonic inheritance of the Neoarchean collision between the Western Dharwar and Eastern Dharwar cratons.