The Central Kerguelen Province(50°-55°S) includes the volcanically active Heard and McDonald islands and contains a major sedimentary basin (Kerguelen-Heard Basin). Recent Ar/Ar dating of the ODP samples showed that basalts from the top of volcanic basement are Albian age (102 Ma). The Albian constructional phase of volcanism, was followed by an Oligocene-Miocene episode that produced mostly intrusive and extrusive volcanics ranging from alkaline basalts to trachytes and rhyolites. Volcanism was confined to the eastern part of the province and around Heard Island.
The Kerguelen-Heard Basin is a 'sag' basin containing more than 2000m of Cainozoic sediments. The basin covers an area greater than 40,000 km2. A prominent seismic reflector (the 'acoustic discordance') within the basin appears to be caused partly by a diagenetic 'front' associated with a Late Paleogene - Early Neogene unconformity. Deformation of the section above this unconformity is caused by deposition dominated by vigorous bottom current activity during the Neogene.