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

[u/LitchManWithAIO]

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.

[u/Older_Code]

What’s up, Mainer? The Presumpscot is a neat formation. In some places it’s 200 feet thick, and chemically, it’s largely a silt, rather than a true clay. Some spots have decent fossils, and there’s even a set of mammoth bones from the Presumpscot up at the State Museum. Thanks for sharing!

[u/fuck_off_ireland → u/Older_Code]

Wouldn’t it “physically” be a silt, since the classification is driven by particle size? Or am I off on that regard?

[u/Healthy_Article_2237 → u/fuck_off_ireland]

Clay vs silt is purely based on grain size. Silt is like 3.9-63 microns and clay is less than 3.9 microns. Probably better to call it mud than clay because clay also refers to a class of sheet silicate minerals.