Kokoamu Greensand
Stratigraphic range: Chattian ~27.3–25.2 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Otiake Group
Underlies	Otekaike Limestone
Overlies	Earthquakes Marl
Thickness	up to 7 metres (20 ft)
Lithology
Primary	Greensand
Other	Limestone
Location
Coordinates	44°42′S 170°30′E / 44.7°S 170.5°E / -44.7; 170.5
Approximate paleocoordinates	50°30′S 176°18′W / 50.5°S 176.3°W / -50.5; -176.3
Region	Canterbury, Otago
Country	New Zealand
Extent	Around Duntroon, South Island
Kokoamu Greensand (New Zealand)

The Kokoamu Greensand is a geological formation found in New Zealand. It is a fossil-bearing, late Oligocene, greensand rock unit of the eastern South Island, especially the Waitaki District of North Otago and the southern Canterbury region. The formation was named by geologist Maxwell Gage in the 1950s. In North Otago it underlies the thicker and harder Otekaike Limestone.^[1] The formation gets its green colour from the mineral glauconite which forms slowly on the ocean floor.

Fossil content

The formation was laid down in shallow seas some 26-30 million years ago. It contains abundant microfossils of foraminifera, ostracods and coccoliths, those of larger marine invertebrates such as the shells of brachiopods, gastropods and scallops, as well as corals, echinoderms, and crustaceans. Vertebrates found in the formation include fish, penguins and cetaceans. Many of the fossils discovered in the formation are held in the Geology Museum of the University of Otago.^[1]

See also