The Haughton Crater
The Impact Crater
The Puijila darwini fossil was found in the Haughton Crater. The fossil's remarkable state of preservation is largely due to the environment of the crater at the time it was deposited.
The Haughton Crater is a 16 km-wide, circular depression on Devon Island in Canada's High Arctic. The crater was formed by the impact of an asteroid or comet that was 1 to 2 km across. Fracturing and other effects of the impact extend beyond the crater's rim, bringing the diameter of the entire structure to 23 km.
Geologists are still uncertain about when the crater formed. In the 1980s, researchers using fission track and argon dating techniques concluded that the crater was about 24 million years old. However, recent age dating using more accurate techniques yielded an age of approximately 39 million years old. Ongoing research by expedition-team member John Gosse aims to resolve the geologic dating of the crater using different techniques.
After the crater formed, a series of lakes developed within it. Following a significant period of erosion of the crater (possibly a few million years), eroded sediments accumulated on the floor of one of these lakes. Over time, the lake vanished but the sediments remained. These deposits make up a geological unit called the Haughton Formation.
These lake sediments contain fossilized remains of plants and animals that lived in and around the lake about 23 million years ago, near the beginning of the Miocene Epoch. This is the only known record of early Miocene vertebrate life at high northern latitudes.
Puijila frequented the shore and shallows at the lake edge and died in the area. We do not know the cause of death, but shortly after the animal died the body sank to the lake bottom, where it was subsequently buried and preserved.
Palaeontology in the Crater
Fossil bones were first discovered in 1978 in the lake sediments. Later palaeontological investigations between 1979 and 2008 found an assortment of plant and animal fossils.
The species represented by the fossils that have been found are diverse in size and kind:
- a rhinoceros (team member Mary Dawson found this remarkable fossil in 1985)
- a small, deer-like animal
- a tiny shrew
- a small rodent
- a relative of the swan.