venturing4th: Blue rocks

Usually we have more difficulty finding a state geo-site from the directions in Albert Dickas' book, 101 American geo-sites you've gotta see, than we have actually seeing the formation. But today was the exception. We googled Brandywine Creek State Park in Delaware and got the address to the Visitor's Center and our GPS took us right there.

The instructions were fairly clear - "on the hillside between the parking lot and the footbridge over Rocky Run are large outcrops that belong to the Wissahickon Formation...." So far so good, there were plenty of rocky outcrops on that section of the trail. The second part is where we got into trouble. The book states - "Approximately 500 feet south of the bridge, darker masses of the Wilmington 'Blue Rock' Complex make their appearance." First off, the bridge had been damaged in hurricane Irene and we had the ford the little stream on slippery rocks. Frederick started counting off the steps from the south side of the bridge and when we reached approximately 500 feet we began looking for rock formations that looked like the picture in the book. We have done this type of exercise several times before, always successfully.

We could find nothing that looked like the Wilmington "Blue Rock" Complex as shown in the book so we kept on walking, and walking, and walking. We could find some bluish looking rocks but nothing like the picture. Finally, after about 45 minutes of walking, we found the most blueish rocks we could and showed Mr. Spock. He agreed that we had done what we could so we walked back to the car to eat our lunch along the shore of the Brandywine Creek.

As we were eating our lunch I studied the book some more and that is when I noticed that there was a picture attribution to the Delaware Geological Survey on the picture we were using. I suspect that Al Dickas used a picture that vividly showed the rocks in the best light and he did not take a picture where he told us we could find the blue rocks. In the future, we will have to be more careful.

Still, it was a beautiful day and we had a nice stroll in the park. There were lots of people using the park where we were. There had been a bike race from 10 - 2 pm today, so there were still some cyclist coming in to the finish. People were also tubing on the creek, fishing, jogging the trail and walking, just as we were.

Oh, the two different types of rocks show the titanic clash of two land masses more then 500 million years ago and the formation of the Appalachian mountain chain, among other things. When fractured, the quartz of the Wilmington Complex often shows rocks that vary from bluish gray to bright royal blue (as was shown in the picture). Named "blue rocks" by nineteenth-century quarrymen, they are so closely associated with the city that its baseball team - a Class A affiliate of the Kansas City Royals - is affectionately named the Wilmington Blue Rocks.

We were in three states to get to today's geo-site in Delaware. Going, we crossed the Commodore John Barry bridge. It spans the Delaware River which forms the border between New Jersey and Pennsylvania.

Under the trusses of the Barry Bridge.

Bicyclists zipping by on the shore of the Brandywine Creek.

The yellow tape marks the finish area.

Signs on the closed bridge over Rocky Run that we needed to cross.

You can just make out the damage to the bridge on the right side of the picture.

Nice layering in this rock.

Mr. Spock agreeing the the blue rocks, just to the right of the fence, is the best we are going to get.

On the north side of the bridge are the outcrops that belong to the Wissahidkon Formation, the metamorphosed remains of sand and mud from the Iapetus Ocean. This section is between the parking lot and the footbridge over Rocky Run.