A few photos from last May’s spring field trip with the Geological Society of Washington… Here’s the group at Chain Bridge Flats (far westernmost-Washington, D.C.), looked at the metamorphic rocks there — a metagraywacke melange known as the Sykesville Formation.
Boulder of Cambrian-aged Antietam Formation quartzite, washed ~25 miles downstream by the Potomac River, bearing characteristic Skolithos trace fossils.
A close-up of the side of this boulder, showing another trace fossil, Diplocraterion, as well as one of the Skolithos tubes.
GSW field trips are free and open to the general public. If you’re in the D.C. area, watch the D.C. Geology Events website for opportunities like this, and then come on along and join the fun!