Skootamatta Lake

SKOOTAMATTA LAKE – Syenite**– South Ontario, Canada

  • Type: Circular formation
  • Diameter:  length  7.5 km, width  4 to 6 km
  • Location: N 44° 50.14’ W 77° 16.7’
LAKE SKOOTAMATTA – east (looking west – courtesy Jon Buchannan sitting in the right seat of GO ZooM). Compare this image with Presqu’ile (below).

The Skootamata Syenite is a large, roundish body centred in Anglesea Township. The body covers an area of approximately 30 km2 , and underlies a large part of Skootamatta and Sheldrake Lakes. Access is provided by county roads east from Highway 41 and the town of Cloyne.


The Skootamatta Syenite is centrally located in the Elzevir Terrane. The body is slightly elongate to the south-southwest with a length of 7.5 km and a width of 4 to 6 km. The Skootamatta Syenite has not been studied in detail. Mapping of Anglesea Township was undertaken by Meen (1944) and was later followed up by the work of Moore and Morton (1986) who cover only the far eastern part of the pluton. These two sources provide all the known information on the Skootamatta body.

**The syenite is a light grey to pale pink, massive equigranular rock. There is a weak foliation in places. The syenite is coarse- to medium-grained for the most part with a minor decrease in grain size towards the contacts. Mineralogy consists of microcline, albite and biotite with accessory sphene, apatite and magnetite. The very low colour index is suggestive of a mafic content of 5% or less. Quartz is present in very minor amounts, varying from trace to 5%, and can only be detected in thin section (Moore and Morton 1986).

Compare this image of the confirmed impact structure at Presqu’ile Lake with Lake Skootamatta syenite (above). There is a striking resemblance between the two structures.

This is a classic example that a circular geologic shape is not firm evidence of an impact event, but it is worth investigating. It took ground explorations of the structures to confirm (in the case of Presqu’ile) or refute (in the case of Skootamatta) an impact event.