Help identifying bedrock

[Metal.detective]

So I'm new to the panning and sluicing game. I've got several good places here in eastern NC. A river is right in my back yard. In this river the bottom is mostly a grayish rock that covers the bottom. HUGE sections of rock...Some places as big as football fields. The rocks are rounded in places and sharp pointy tops sticking out in other places. Is this bedrock? I'm going to try and go out digging for a little while today if the rain lets up and they aren't generating to much and have the river up. I'll take some pictures to get a visual aid for y'all to see. Thanks for the help.