PILOT LAKE IMPACT CRATER
by: Charles O’Dale
- Type: Complex
- Age Ma: 445 ± 2a – ORDOVICIAN
- Diameter: 6 km
- Location: N 60° 17’ W 111° 1’
- Shock Metamorphism: PDF and breccia with a melt matrix
a pre-1977 K-Ar, Ar-Ar and Rb-Sr ages recalculated using the decay constants of Steiger and Jager (1977) Ages in millions of years (Ma) before present. The relatively high quoted age precision of the structure was obtained from a single impact related rock sample (breccia with a melt matrix). Based on this, the age should be viewed with caution (Grieve 2006).
ABSTRACT: Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably ‘rubble pile’ asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids.
Evidence that Pilot Lake, an eroded impact structure, was collected in 1965. Planar deformation features in quartz occur in some of the discovered brecciated gneiss boulders found around the site (Grieve 2006).
The lake depths were found to be larger than for neighboring lakes. The bottom was found to be nearly flat and covered with sediment. On the western lake shore granite gneiss was found, conspicuous because of its highly fractured condition, similar to the rocks found around the Brent crater. Microscopic examination of the rocks revealed PDF, and the small pieces of impact breccia was similar to the Brent breccias (Hodge 1994).
We took these images of the Pilot Lake Crater flying in from the north and leaving the area to the south. As illustrated in the images we took while flying over the structure, the lake is an excellent “sign post” for pilots flying over the area.
Brent Dalrymple, Radiometric Dating Does Work! Reports of the National Center for Science Education
Dence, M. R., Innes, M.J.S. and Robertson,P.B., Recent geological and geophysical studies of Canadian craters. in Shock Metamorphism of Natural Materials, eds. B. M. French and N. M. Short, Mono Book Corp., Baltimore, MD, pp. 339-362. 1968.
Grieve R.A.F., Impact structures in Canada, Geological Association of Canada, 2006.
Hodge, P. Meteorite Craters and Impact Structures of the Earth, Cambridge University Press, 1994.
University of New Brunswick, 2012.