Mesozoic Antarctica

Antarctica hasn't always been the cold, icy continent that it is now. In the Mesozoic Era, 60-250 million years ago, Antarctica was lush and green. The Mesozoic (meh-su-ZO-ick) Era is the period of Earth's history when dinosaurs ruled the Earth. (The Mesozoic Era is divided into three periods: the Triassic, Jurassic, and Cretaceous. Those are probably names you're more familiar with.)

During the Mesozoic, the entire plant was warmer, so the poles were not as cold as they are now. There were vast forests of conifer trees and huge ferns growing in Antarctica! Why was the Earth so warm back then? Geologists have learned that there was rapid sea floor spreading. Magma was quickly venting to the surface, and along with it came a lot of CO₂ (a greenhouse gas) into the atmosphere, making it a very warm planet.

The warmer temperatures meant life could spread across the continent. It wasn't such a harsh habitat back then! We know there were plants growing at that time because we find fossilized pollen spores, pieces of wood, and even whole plant leaves. Imprint of the leaves can be found in sandstones and mudstones, creating pictures of the leaves that last for millions of years. 

Fossil print of a fern near my foot.

These plants provided food for many other organisms that lived in Antarctica at the time. There were insects, arachnids, and even dinosaurs, birds, and marsupials in Antarctica! Their fossils are commonly found at the northern end of the Antarctic Peninsula.

I do not work in the parts of Antarctica where dinosaur fossils are common, but I have come across the fossils of marine organisms that date back to this time period as well. The Antarctic Peninsula has a lot of fossilized prehistoric mollusks, including cephalopods (modern day members are squids and octopi) and bivalves (like clams).

Belemnite fossils in rock from Alexander Island.

Fossilized imprint of a bivalve. (Sorry, it's a little blurry!)

Antarctica was ice-free like this until about 35 million years ago. The Earth cooled and the Antarctic continent shifted further south, making it the polar ecosystem that we know today. Most people don't know that it was once very lush and green. It's fun finding traces of that history when we are bundled up against the cold in the field!