Viewfield
Key facts
- Country
- Canada
- Diameter
- 2.5 km
- Age
- about 190 ± 20 million years
- Location
- 49.58° N, 103.07° W
Nothing: the crater lies about 1 km beneath the farmland of south-eastern Saskatchewan.
Viewfield is a small buried impact crater about 2.5 km across in south-eastern Saskatchewan, in Canada. It has been an oil field since the late 1960s.
Discovery. In 1969 an oil well drilled in the area struck oil in an unexpectedly thick zone of broken rock. Seismic surveys and further drilling revealed a round, bowl-shaped structure with a raised rim. Study of the cores later showed breccia and shock features, and the structure was identified as an impact crater.
What it hit. The impactor struck a sequence of Palaeozoic sedimentary rocks, mainly Mississippian limestones and dolomites, in the Williston Basin. The crater was soon buried by Jurassic sediments.
Age. The youngest disturbed rocks are Triassic and the oldest rocks lying over the crater are Jurassic, so the impact happened around 190 million years ago, give or take about 20 million years.
Oil. Oil collected in the broken rock of the crater rim, which acts as a reservoir, sealed by the sediments above. The field has produced millions of barrels.
Why it matters. Viewfield is one of the clearest examples of how a small impact crater can create an oil trap, and its discovery encouraged oil companies to look for others. The impactor is unknown.
Did you know?
Viewfield was discovered in 1969 when a well struck oil in broken rock.
Oil collected in the broken rock of the crater rim.
The crater lies about a kilometre underground.