For part three I want to discuss glacial outwash deposits. First of all, glacial outwash deposits are large deposits of sorted glacial material that have been washed down stream generally beyond the terminal moraines of the glaciers. These could have formed while the glacier was present or after it receded, and the streams and rivers changed their courses.
One of the interesting things about some of these larger outwash deposits is that they consist of multiple eras of glacial gravels, even on the N-S waterways. This is because they consist of the material that the glacier bulldozed out of the river channel each time the glacier advanced south. The massive amounts of water that came from the melting and receding glacier would have worked and moved all the material that had been piled up in the channel at the terminal end of the glacier. These waters sorted, concentrated and moved the outwash gravel miles and miles down the part of the river channel that was not glaciated.
These unglaciated channels that have the outwash gravels in them also have a good chance of having shallow bedrock since the channel was never cut out by the glaciers. The few outwash areas of prospected in western PA and eastern Ohio that are beyond the glacial limits have produced gold and generally have exposed bedrock in places.
The sheer volume of material that has been outwashed beyond the end of the glaciers boggles the mind and should have good placer gold potential. One of the draw backs is that so far as I have read and seen in the field is that these larger outwash deposits are also generally covered by a skim of recent alluvium that is generally not good bearing. So one must get through this upper layer of barren material before getting to the potential good glacial outwash under it.
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