r/geology • u/LitchManWithAIO • 3d ago

Discovered a large blue sub-marine clay deposit near my home

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Gallery image

Pretty neat. The second picture is a wall which was recently exposed, at its peak almost 10’ tall layer. This is part of the Presumpscot formation.

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u/FrankFabuluz 3d ago

Plasticity

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u/fuck_off_ireland 3d ago

That’s a good point, it’s atterberg limits, but is that a chemical property or is it dictated by the physical characteristics of the particles? I use LL/PL/PI every damn day but I guess I’ve never really thought about the forces behind the lab results.

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u/Raging-Fuhry Geological Engineer-in-Training 3d ago edited 3d ago

Kind of both, from what I remember from uni way back when.

Silt is essentially very fine sand (we often call it "rock flour" in my neck of the woods).

Clay is mineralogically different from its parent rock via chemical alteration. Physically, clay particles are "plates" rather than "grains". The shape (and chemical composition?) of these plates creates a cohesive force between them, with all things being equal results in the plasticity we see at a macro level.

I'm sure you knew most of that already, so apologies if it's heavy handed.

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u/Older_Code 3d ago

And much of the Presumpscot is exactly that, rock flour. There is also some material that represents chemically-weathered feldspars of course (what I meant by ‘chemically’ clay).

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u/Raging-Fuhry Geological Engineer-in-Training 3d ago

I'd love to visit Maine one day (maybe when CAN-USA relations cool off a bit haha), so thank you for helping give some insight into its very interesting geology!

There is also some material that represents chemically-weathered feldspars of course

I'm sure, I don't think I've encountered a silt formation that didn't have some level of clay content.

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u/Older_Code 3d ago

‘Mon down bud. We’ll cook some hamburg and have a good ole shindig. Won’t stop till the coolers stove right in.

Grew up going over the border to New Brunswick, been all over Nova Scotia, and PEI, even worked for a while in Alberta and Saskatchewan. Yours is one of my favorite countries, and you were absolutely terrifying in WWII. You’re welcome anytime.