Oakland Geology

As far as I can tell, Oakland has more rock types within its boundaries than any other city in America. When I added them up for a talk I gave at East Bay Nerd Nite, I counted more than 25, from limestone to blueschist. This 30-mile road trip will take you to most of them, with the Hayward fault as a bonus. It starts above the UC Berkeley campus and runs south the length of the high hills, then goes back north through Montclair and Piedmont to end at Mountain View Cemetery.

That’s 1200 pixels wide if you click on it, but don’t worry, I’ll show it in pieces below for more detail. In fact, let’s go to part 1 right now. It goes from Grizzly Peak through Joaquin Miller Park on Grizzly Peak and Skyline Boulevards.

The numbered segments correspond to the formations on the geologic map, as follows:

1. Moraga Formation (basalt, andesite, tuff)
2. Orinda Formation (conglomerate)
3. Claremont Shale (chert, shale, dolomite limestone)
4. Sobrante Formation (mudstone, shale)
5. Unnamed mudstone/sandstone
6. Redwood Canyon Formation (sandstone, siltstone)
7. Shephard Creek Formation (sandstone, mudstone, siltstone, shale)
8. Oakland Conglomerate* (conglomerate, sandstone)
9. Joaquin Miller Formation (sandstone, shale)

Then there’s part 2, from Joaquin Miller Park to the edge of Montclair on Skyline, Grass Valley Road, Golf Links Road, Mountain Boulevard, Keller Avenue, Campus Drive and Redwood Road.

1. Serpentine (serpentinite, blueschist)
2. Oakland Conglomerate* (conglomerate, sandstone)
3. Knoxville Formation (conglomerate, shale)
4. Leona volcanics (metatuff, metabasalt)

Part 3 takes the freeway to Montclair Village, where you won’t see any rocks, then goes down Moraga Road to Piedmont’s Dracena Park and over to Mountain View Cemetery, where rocks are abundant.

1. No rocks to be seen, but do stop on Medau Place and spot the offset curbs where the Hayward fault crosses it
2. Franciscan melange (argillite, metachert, greenstone)
3. Franciscan sandstone (sandstone, siltstone)
4. Franciscan melange

The cemetery’s melange has many bodies of hard rock (knockers) that stand above the ground. They have their own blog category. Search this site, or check the category list on the right, for posts I’ve written about these rock units.

*The cobbles embedded in the Oakland Conglomerate offer more rock types, including granite, quartzite, gneiss and schist. That’s how I get up to 20.

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