Couture
Key facts
- Country
- Canada
- Diameter
- 8 km
- Age
- about 430 ± 25 million years
- Location
- 60.13° N, 75.33° W
Lac Couture, a round lake about 8 km across in the Arctic tundra of northern Quebec. Boulders of impact melt rock lie along its shores.
Couture is an impact crater about 8 km across, filled by the round waters of Lac Couture in the Nunavik region of northern Quebec, in Canada.
Discovery. The round lake was noticed on aerial photographs and maps during a systematic search for impact craters on the Canadian Shield in the 1960s. Geologists visiting the lake found loose blocks of impact melt rock, rock that had been completely melted by the impact and then cooled, and impact breccia along the shores and in glacial deposits south of the lake. Ice sheets had scraped these rocks from the crater and carried them a short distance. Shock features in quartz and feldspar in these blocks confirmed an impact.
What it hit. The impactor struck ancient crystalline rock of the Canadian Shield, mainly granite and gneiss more than 2.5 billion years old.
Age. Argon dating of the melt rock suggests an age of about 430 million years, in the Silurian, with an uncertainty of about 25 million years.
Why it matters. Couture is one of several crater lakes in northern Quebec, along with Pingualuit, Clearwater Lakes and La Moinerie, that show how common impact craters are on the ancient, stable rocks of the Canadian Shield. The impactor is unknown.
Visiting. The lake is extremely remote and can be reached only by aircraft.
Did you know?
Lac Couture was identified during a 1960s search for impact craters in Canada.
Ice sheets carried blocks of melted rock out of the crater.
The crater is completely filled by a lake.