East Tasman Plateau
[4] In the late Cretaceous the East Tasman Plateau was at 65°S and it moved north to 60°S in early Oligocene.
The earliest continental East Tasman Plateau rocks that have been brought to the surface of the sea are of Neoproterozoic age, and include gneiss, rhyolite, quartzite, sandstone, ferricrete, and metamorphosed sediments.
[3] The eastern edge of the plateau facing the Tasman Basin is steep, dropping more than 1,000 metres (3,300 ft) and composed of granite.
[5] From early to mid Eocene, 55 to 37 Ma, the climate on nearby land was uniform, wet and cool and supported angiosperm forests.
[5] During this period around 36 million years ago the plateau started sinking to a depth of 300 metres (980 ft).
[6] The sinking has been at the rate of 1 kilometre (0.62 mi) in 10 million years (0.1 mm/year), so the buildup of sediments is not keeping pace with submergence.
The sediment cores from the East Tasman Plateau give a history of the temperature of the Southern Ocean and are valuable in seeing the limits of climate change in the future.
[10] The top of the seamount is fairly flat and domed, but once down to 900 m (3,000 ft) deep the sides slope off very steeply.
[10] The Cascade Seamount is a volcano formed during the Late Eocene period as a result of the Balleny mantle plume.
[11] High frequency echograms show that the top of the seamount is covered in sediment, but that the steep slopes are rocky.
[13] Above the sea at this location typical Southern Ocean animals are found such as several kinds of whales, albatross and petrels.
[14] Molluscs found on the Cascade Seamount include Cuspidaria brazieri (Brazier’s spoon-shell), Cuspidaria erma (noble spoon-shell), Veprichlamys perillustris (shining scallop), Fusitriton magellanicus retiolus (Magellanic rock-whelk), and Sassia kampyla (curved rock-whelk).
