Last May, we took a long weekend to go dig fossils at the Stonerose Interpretive Center in Republic, WA. The fossils are from the Eocene epoch (about 50 million years ago), when eastern Washington was tropical. The city of Republic was part of an ancient lake.
For a nominal fee ($6/person plus $4 for hammer + chisel rental), you can dig in the fossil bed north of town. They reserve the right to inspect them in case you uncover a new species, but allow you to keep up to three fossils per person. A benefit of inspection is they’ll also tell you what it is. You can also keep a sample of the lake bottom, worm tracks, and some other stuff. In all, we ended up with a lot.
From their web site:
Over many years, layers of sediment built up on the lake bed. Much of this material was powdery ash from volcanic activity occurring in the area.
These layers of the old lake bottom can be seen today as layers of fine-grained tuffaceous shale, volcanic ash hardened into sedimentary rock. The layers of shale split apart like pages in a book revealing fossils and information about the ancient lake and its surrounding vegetation. Within these layers, the insects and fish that drifted to the lake bottom, and the leaves and twigs that floated downstream or blew into the lake can now be seen as fossils.”
This is a sample of the lake bottom:
Here are examples of worm tracks: