Clay Bottom Question

[mu50stang]

I'm working a creek in Indiana that has a grey clay bottom. With Indiana being glacier gold or flood gold, should I try and dig past the clay to see whats there. I'm dredging so I would have to shovel it cause its real hard. Would it even be worth the time to try and dig it. Thanks.

 

[GrayCloud]

Post hole through it. This will give you the clay layer depth and a sample of what is under it.