Looks like you are in my buddies back yard. Literally... lol. Still it's a good place to mess around as long as they don't come tell you it's private property but I've never had a problem there

The actual river bottom is at least 40 feet down right below where you were standing in the middle of the canyon. Everything there underneath you is tailings from the mines up on the east side of the main channel. So where you were digging
IS on the inside bend, but you have to imagine that originally the river naturally flowed 40 feet beneath you before the tailings from the sluice in " ____canyon" upstream from you filled the canyon with those hydraulic tailings. This video is from a few miles away from where you were.
The old
Red Dog Cemetery | Nevada Cemetery District is not far from where you were up on the east hill. I have relatives buried there and a lot of history in the area. A good book for you to read is
You Bet gold fever: A true documentation: Jerry Brady: Amazon.com: Books where it tells about my Great Aunt Nettie being the only person to ever witness a murder in the town. The books are rare these days but worth reading. I used to dredge on Jerry's property back in the day