Lower Piedmont Park walk (#28)

Walk number 28 in Charles Fleming’s Secret Stairs East Bay winds around the fine homes and hills of Piedmont along the valleys of Wildwood and Bushy Dell creeks. Here’s the route, shown on the Google Maps topo base.

walk 28 topo

The first and last part of the loop is in the watershed of Wildwood Creek while the rest is in the Bushy Dell Creek watershed. (They run down Lakeshore and Grand Avenues respectively, separated by Warfield ridge, and combine down at Lake Merritt where their names are sunk in bronze by the pergola.) Geologically, the walk covers the uppermost part of the big Pleistocene alluvial fan and the edge of the Franciscan bedrock block that underlies most of Piedmont.

geologic map

We start at the Lakeshore-Winsor split in the stream valley and make our way toward the divide. On Portsmouth Road the high ground of the bedrock zone stands out ahead.

At the far end is a steep climb to Wildwood Avenue, where we can look back across the stream valley to the ridge topped by Calmar Avenue, on the Oakland side of the city line.

Turning the other way, we look over the valley of Bushy Dell Creek. Once a large formal garden, this part of the valley was filled and leveled for its current use as a sports complex. It appears never to have been a quarry, unlike Dracena Park to the north or Davie Tennis Stadium to the south.

We turn upstream along the creek, where the land is relatively untouched. Just above this spot is the site of what was reputed as a sulfur spring.

The geologic setting doesn’t really give much support for the presence of a proper sulfur spring like the one in Walnut Creek, but after all this time the question is moot. Certainly I didn’t notice any odor. The grotto was very pleasant anyway, and there’s real bedrock all around. It’s mapped as Franciscan sandstone of the Novato Quarry terrane.

The route goes farther up and takes a loop past a pair of boulders.

Take a close look at these: they’re genuine Oakland-style blueschist, globs of old ocean crust that have been carried tens of kilometers down into the earth along a subduction zone, then spat back out, possibly more than once. (The details are at the bleeding edge of California geology.) The one boulder displays good color and mineralogy:

The other has some nice slickensides to show us.

Coming back downstream and past the baseball diamond, we pass the entrance to the football field. The view looks down the valley toward the lake and downtown.

Near here we can see more exposures of the sandstone bedrock, but soon afterward the route returns to the alluvial fan. The two substrates make subtly different topography, but that can be hard to see given the heavily landscaped landscape.

Palm Drive offers a picturesque farewell view of the Bushy Dell Creek valley.

Again we cross the divide between the two watersheds at Wildwood Avenue. The near valley is accentuated by glimpses of the higher hills.

I never get tired of this stuff.

Here’s the route in more detail.

route map

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6 Responses to “Lower Piedmont Park walk (#28)”

  1. Ann Wilkins Says:

    Hi Andrew, About how long is this walk i.e. 3 miles and a little over an hour? Longer? Shorter? Would be interested in taking the walk.

  2. Andrew Says:

    It’s just under 2 miles. I recommend that you buy the book if you like walks like this. My versions of these hikes focus on the geology, but the book is about historical and cultural sights—and paths and stairs, of course. The book has detailed directions that I don’t include here.

  3. Kathy Yam Says:

    Where is the photo of the two boulders with the slickensides and minerology and path between them? I walk in Piedmont Park most every morning and I don’t recognize that spot. I am curious. Also, there are several sulphur springs in Piedmont Park. Most notably next to the path under the big Eucalyptus tree at the fork in the road. It has been running pretty well this summer. Sometimes it is very stinky and other days it is not. There is black H2S silt in the spring. Another sulphur spring is under the patio behind the Community Center.

  4. Kathy Yam Says:

    I found the spot with the boulders this morning with the help of some friends. Slickensides and all! Now it is obvious. We don’t usually approach the boulders from that direction.

  5. Andrew Says:

    Thanks for that info, Kathy! I must poke around there some more.

  6. Andrew Willats Says:

    I teach environmental science at Piedmont High School, directly adjacent to the park. Unfortunately, we don’t have a geology class, but I wonder if you have some more specific suggestions for examples of the formations you discuss, such as the two boulders. Also, geology is not my strong suit – any suggestions for an East Bay specific reference book or another website? Thanks!

    [Geology of the San Francisco Bay Region by UC Press is an excellent, inexpensive guidebook with a decent introduction to the basics of the science.

    The only website on East Bay geology, or Bay area geology for that matter, is this one. —Andrew]

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