Kokoamu Greensand facts for kids

Quick facts for kids Kokoamu Greensand Stratigraphic range: Chattian ~27.3–25.2Ma PreЄ Є 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

The Kokoamu Greensand is a special type of rock layer found in New Zealand. It's known for having lots of fossils! This rock unit formed about 26 to 30 million years ago, during a time called the late Oligocene epoch. You can find it mostly in the eastern part of New Zealand's South Island, especially around the Waitaki District and southern Canterbury Region.

What is Kokoamu Greensand?

This rock formation gets its name from geologist Maxwell Gage, who named it in the 1950s. It's called "greensand" because of its unique green color. This color comes from a mineral called glauconite, which forms very slowly on the ocean floor.

The Kokoamu Greensand is a layer of rock that lies beneath another, thicker rock layer called the Otekaike Limestone in North Otago. It's like a sandwich, where the greensand is the bottom slice of bread.

How it Formed

The Kokoamu Greensand was created in shallow seas millions of years ago. Over time, sand and tiny bits of marine life settled on the seabed. The glauconite mineral slowly grew, giving the sand its green tint. This process happened over a long period, eventually forming the rock layer we see today.

Fossils Found Here

The Kokoamu Greensand is famous for its many fossils. These fossils tell us a lot about the ancient life that lived in the seas around New Zealand millions of years ago. Scientists study these fossils to understand Earth's history.

Tiny Fossils

This rock layer contains many tiny fossils, often called microfossils. These include:

• Foraminifera: These are like tiny amoebas with shells.
• Ostracods: Small crustaceans, often called "seed shrimp."
• Coccoliths: Even tinier, these are plates from single-celled algae.

Larger Marine Animals

You can also find fossils of bigger marine animals in the Kokoamu Greensand. These include:

• Shells of brachiopods, snails, and scallops.
• Different types of corals.
• Echinoderms, like sea urchins and starfish.
• Crabs and other crustaceans.

Ancient Vertebrates

Some amazing vertebrate fossils have also been found here. Vertebrates are animals with backbones. These include:

• Various types of fish.
• Ancient penguins.
• Early whales and dolphins.

Many of these incredible fossils are kept and studied at the Geology Museum of the University of Otago.

Ancient Penguins

The Kokoamu Greensand is especially important for understanding the history of penguins. Several species of ancient penguins have been discovered here:

Ancient Whales and Dolphins

This formation also provides clues about the early evolution of whales and dolphins. Here are some of the ancient cetaceans found: