The Basics

Inspired by the beautiful rock-cuts found on the highway between Sudbury and Orillia, I'm going to create my own geology guide to this stretch of highway. I could probably find a site that has already done this but I want to learn it.

The Basics

This map gives the central divisions:
The GREEN areas were covered by oceans attached to the Great Lakes and Hudson Bay, so they have simple newer deposits and fossils. Everything that is not GREEN is super-old and scrapped clean.
The PINK is the Canadian Shield - a layer of primordial granite formed by the super-volcanoes that were forming "land" instead of lava. This is the basement level but its great age means it has been folded and heated many times, including fault-lines that lead to lava eruptions bringing precious metal to the surface (aka 'greenstone belts')
The PURPLE areas are deposited metamorphed sedimentary and volcanic rocks that "rest uncomfortably on Archean granitic" below. Generally low-grade or minor. This is known as the 'Huron Supergroup' and is only slightly younger than granite beneath.
The YELLOW  the geological region called the "Grenville Province". It is considered part of the Canadian Shield but it is the youngest part and it has been squished against the older granitic part.
This squishing has made it a geologically complex with sheets of lands being pushed under and over each other. For example Parry Sound seems to be a piece of the Adirondac Highlands that got shoved around until it thrust out up here. Once you drive east of Sudbury you are immediately in the Grenville Provice, and you stay in it until you hit Lake Simcoe, so this will be our focus.

My main resource will be *Ontario Geological Survey - Open File Report #6143* which covers the geology of Georgian Bay's eastern shore.


The full range of the Grenville Province

The Grenville Province - Gathering Clues

What is the 'Grenville Province'?

This #academic webpage# tells me what the Grenville Province is - but I cannot yet understand it. So the project for this week is understanding this.



Wikipedia: "The Grenville orogeny was a long-lived mountain-building event that happed on the supercontinent Rodinia a million years ago. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland" [orogeny = continental plate crumples and is pushed upwards]

The Ontario portion has "not undergone any regional metamorphic overprinting" since it formed.
The Parry Sound section is full of "migmatitic quartzite, gneiss, anorthosite, and gabbro"