The gravel bench is about 15 feet from the active rivers edge. No not under a big rock. I did get fill in or maybe the water table fill the bottom five inches of my hole. It is inside a slight bend with large sandy gravel where I dug.
OK, good info.
Sounds like you are digging in a high water flood deposit. The gold you described is typical for that type of zone.
Without knowing the river I can only tell you some basic understandings.
The bigger the rock the better the gold.
Gold follows the gut of the river. The gut is the center of the main water flow during the peak of the flood.
The river rearranges the loose material and as the flood starts to slow the gold stops and is buried.
This is why underwater dredging is so popular.
The heavy gold stops first.
The High banks of a river may have been in the rivers gut in the ancient past and hold good gold.
If you are in a river valley and the valley walls have river rounded rocks exposed the is a good chance there is gold there.
Miners say Gold is where you find it, but it aint always where you look.
I live in So California. I do most of my mining at the San Gabriel East Fork River.
Good gold there. Not always easy to find, but worth looking for.