AT THE BOTTOM (OF INDIA): PROTEROZOIC PALEOMAGNETISM AND GEOCHRONOLOGY OF THE SOUTHERN GRANULITE TERRAIN

The site-level combination of paleomagnetism and geochronology is being increasingly used to track Precambrian terranes through deep time. The Southern Granulite Terrain (SGT) of India is a collection of highly metamorphosed crustal blocks of Archean to Neoproterozoic age in Southern India. There has been limited paleomagnetic and geochronological work of varied quality done on the numerous Proterozoic mafic dykes hosted in the northern blocks of the SGT. Mafic dykes are excellent recorders of the ancient geomagnetic field due to favorable geochemistry, rapid cooling, and suitability for field tests of remanence age. New techniques for isolating minerals (zircon/baddeleyite) for U-Pb dating make the dykes a useful target for precise geochronology. In this study we examined dyke swarms in the Northern (Salem) block of the SGT. The age of contiguity of the SGT with the Dharwar Craton to the north is a matter of debate. Comparison of paleomagnetic data from the Dharwar and the SGT will test their connection. In addition, these paleomagnetic data can be utilized in reconstructions of India in the various posited Proterozoic supercontinents (Columbia, Rodinia). Paleomagnetic data from 51 sites – demagnetization, rock magnetic properties, and field tests – in the Southern Granulite Terrain will be shown along with discussion of the paleogeographic consequences of these data. Preliminary pilot demagnetization reveal that the majority of sites (>40) carry a stable remanence component unrelated to the present day field.