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JUAN EMMANUEL

Georgian Bay Formation “Bent” Rocks

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JUAN EMMANUEL

Hi guys, I visited Mimico Creek 2 days after the Canadian Thanksgiving this October which also happened to be a really hot day, which was perfect for exploring. 

During my time hunting the Georgian Bay Formation of Toronto I would come across these exposures that look “folded”. Does anyone happen to know as to what this really is? Here is a pic I took on that trip I mentioned to show as an example.

I would find the same distortion in other parts of Toronto, not just in Mimico Creek, but also in places like along the Humber River and Etobicoke Creek.

CEE75BAC-47EB-4222-9582-721E9799D38E.thumb.jpeg.a329a1ef982756bd8383d931941e503c.jpeg 

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DPS Ammonite

Your photo above is a section of folded shale, siltstone and stone. Compressional forces from the right and left created it. See: 

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Mississauga Geology - close up of the Georgian Bay Formation

 

The City of Mississauga is underlain by bedrock formed during the Palaeozoic Era. The Queenston Formation and the underlying Georgian Bay Formation were both formed during the Ordovician Period (400 to 425 million years ago) when this area was covered by a shallow warm sea.

The Georgian Bay Formation has been classified as Upper Ordovician in age. It consists of blue-grey and green-grey shales with interbedded sandstone, green-grey siltstone and grey argillaceous (very fine grained) limestone (Bond et. al. 1976). The harder interbedded units occur with increasing frequency towards the top of the unit. The limestones and siltstones also contain abundant fossils. The shales of the Georgian Bay Formation are exposed in numerous places along the walls of the Credit River valley and it’s tributaries.

The contact with the overlying Queenston Formation is gradational and is exposed within the City along the steep-sided valleys of the Credit River. The Queenston Formation is a very distinctive red-shale, characteristic of much of the area below the Niagara Escarpment. It is Upper Ordovician in age and has been described as thick bands of dark red, iron rich (hematitic), fissile, calcareous shale, interbedded with very fine grained, homogeneous, grey to green layers of limestone. The Queenston Formation is exposed along creek valleys in

the Streetsville area, to the north along Fletchers Creek and as part of a shale plain just north of the Queen Elizabeth Way along the western border of the City.

 

https://www.flickr.com/photos/reighleblanc/7611696250

 

 

 
 

 

 

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ynot
11 hours ago, JUAN EMMANUEL said:

Does anyone happen to know as to what this really is? 

Looks like normal geologic folding caused by mountain building processes.

 

2 hours ago, DPS Ammonite said:

This is a section of folded shale, siltstone and stone.

I see nothing "folded"in Your picture(?).

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FossilDAWG

That sort of very small-scale folding is, I think, produced by local slumping or slipping on the soft deformable shale layers.  Also bear in mind that ~12,000 years ago there was 3-4 km of moving ice on top of those rocks.  The movement and weight of those glaciers could easily have produce local folding like you are seeing.

 

Don

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DPS Ammonite
59 minutes ago, ynot said:

Looks like normal geologic folding caused by mountain building processes.

 

I see nothing "folded"in Your picture(?).

Poorly written. I meant to refer to the poster's photo above. I also added

the text to the flicker photo. 

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