ESTIMATING SEA LEVEL DUE TO CRUSTAL STRETCHING OF THE MARGIN OF THE INDIAN OCEAN

Continental crustal extension is a precursor to the formation of a new ocean. The overall crustal extension causes change in the volume of global oceans hence change in sea level. The break-up of Gondwana that began during Late Triassic to Early Jurassic time caused continental crustal extension prior to forming the Indian Ocean. Extension started 184 Ma with rifting between SE Africa, Madagascar and Antarctica. This was later followed by rifting between Greater India, Australia and Antarctica beginning about 160 Ma. The most recent episode of extension occurred 34 Ma involving separation between Arabia and Horn of Africa. Gridded data sets including the age of oceanic crust, the current thickness of oceanic sediment and water depth coupled with a compilation of deep sea sediment porosity from Ocean Drilling Project data allows us to quantitatively determine the change in volume of the ocean displaced by extension of continental crust and its impact on the global sea level. Analysis of this data is divided into two parts: Spatial analysis using the gridded data sets and; Tectonic subsidence analysis using backstripping. A large amount of extension is observed in Australia, NE Antarctica, South Africa and India; we also see a small amount of extension in East Africa, the Horn of Africa, Arabia, and North and NW Antarctica. Our results from the margin of the Indian Ocean demonstrate that continental extension generated a 6.5 m rise in global sea level, which occurred mainly between 160 Ma and 100 Ma.