Holleford RASC GA Tour



  • Type: Simple
  • AGE(ma): 550 ±100 a
  • Diameter: 2.35 km
  • Location: Ontario, Canada N 44° 28′ W 76° 38′
  • Shock Metamorphism: PDF in quartz grains (Robertson, Bunch, 1968)

a Dating Method: Geological – estimated to be in the latest Proterozoic or earliest Paleozoic times (Grieve 2006).

The Holleford Impact Structure is located 27 kilometres north of Kingston and 132 kilometres south-west of Ottawa in southern Ontario. Confirmation of the structure as an impact site dates only to the mid-1950’s. Several farms had been maintained at the site and the in the recent past aircraft have been flying overhead without anyone noticing that this may be an “unusual” structure. This is not surprising as the depth of the structure is only ~ 30 m (Beals 1960).

A systematic study of 200,000 aerial photographs of areas of the Canadian Shield was commenced in the early 1950’s when the Pingualuit Crater (formerly Chubb and then New Quebec) and the Brent Crater were confirmed as impact structures. As a result, Holleford was identified as a “structure of interest”. Over the years since that search, scientists have pieced together much of the Holleford Structure’s geological history (UNB 2003)


(Airphoto A1161-43) First identification of the feature was a result of a 1955 study of 200,000 aerial photographs of areas of the Canadian Shield conducted by the Dominion Observatory under the direction of Dr. Carlyle S. Beals, the Dominion Astronomer at the time.





Profile of the Holleford Crater as reconstructed from drill-hole and surface observations. It will be seen that the original crater surface dips nearly 800 feet below plain level, while the zone of fractured rock extends to an estimated depth of about 2,400 feet. The estimate of breccia depth at the centre depends on theoretical considerations advanced by J.A. Rothenberg.



THE HOLLEFORD CRATER – A meteorite travelling 55,000 kilometres per hour (15.3 kilometres per second) smashed into the earth here eons ago, blasting a hole 244 metres deep and 2.5 kilometres wide. Aerial photographs revealed the crater in 1955, and since then scientists have pieced together much of its geological history. Analysis of drill samples suggest that the meteorite struck in the late Precambrian or early Cambrian period (between 450 and 650 million years ago). At first the depression filled with water, becoming a circular lake. Later, Palaeozoic seas swept in sediments, filling the crater to its present depth of about 30 metres. The explosive impact of the meteorite (estimated to have been only 90 metres in diameter) is still evident in the hundreds of feet of shattered rock that drilling has detected beneath the original crater floor.