Looking for petroglyphs on the Wissahickon

My son and I took a hike to see an old dam on the Wissahickon Creek, part of the Wise's Mill complex formerly occpying this stretch of the creek. The damn is constructed at a minor narrowing of the creek, between two sets of large, riverine boulders. It is a picturesque location. It's long been held by locals that the Lenape considered the Wissahickon Valley a sacred place, or at least a "haunted" one (to the extant that a distinction was made). With legendary locale's such as Devil's Pool (purportedly the site of a great spiritual battle) and (local witch ) Mom Rinker's Rock, the Valley has the potential to yield a great many lithic surprises.


After some foraging along the river bank below the dam, we moved closer to it, and took special notice of the large boulder at the foot of the falls. It is seen here slightly left of center in this image, behind the leftmost tree. It was possible to get closer to this boulder, and of course, we did so. We were rewarded for our efforts with the following image:


Ancient Native American petroglyphs? Maybe there are some cursory similarities to a few of the Safe Harbor Petroglyphs, but for the most part, not really. The Ogham alphabet? Please. Some miller's idle scratchings? Who knows? Natural anomaly? Could be.

The fun of doing this is that I just don't know what I'm looking at. Speaking as a scientist, there isn't a better feeling in the world.