There’s a little corner of Lake Merritt that the improvers haven’t gotten around to, on the north shore by the pergola. Here the concrete walkway gives way to a stretch of old fill.
The original wetland that became Lake Merritt was known as San Antonio Slough. From Oakland’s earliest days, the locals kept trying to “reclaim” it by turning it into dry land, just as they did all around the bay. The whole waterfront is reclaimed land. The basic technique was to haul dirt and rock and rubbish down to the water, shove it in and tamp it down. In Gold Rush San Francisco they’d use abandoned ships for fill, but Oakland’s founding fathers had advanced beyond such crude strategems.
Some of this material came from the holes dug for building foundations, but it also came from quarries in the local hills ranging in size from little borrow pits to big enterprises like Blair’s Quarry (now Dracena Park) in Piedmont. Not just stone, either—Oakland had abundant gravel nearby, too. But a good share was probably rock from the macadamized streets, recycled as they were replaced with asphalt and concrete starting in the late 1800s.
If they weren’t trying to fill it in, the makers of Lake Merritt were trying to elevate its mucky shoreline and civilize it. The rocks in this part of Lake Merritt appear to be good old Franciscan chert, possibly from the “phthanite” diggings that the Realty Syndicate exploited in today’s Moraga Canyon. It made quality fill, hard and clean and compact. I don’t know how long it will stay visible as we continue to civilize the lakeshore. Visit it some time when you’re on a walk around the lake and the ground is washed clean. The more we kick it and scuff it and curse it for stubbing our toes, the more its polish gleams.
[Update: Since the date of this post in late 2014, this stretch of the lakeside path has been covered with concrete, to the relief of everyone with feet.]
Oakland Geology 
20 February 2015 at 1:02 pm
Thanks Andrew, I like your suggestion that the stones may from a building demolished as a result of the 1906 earthquake, and thanks also for the lead on the sandstone quarry on the peninsula – I hadn’t made the connection to those buildings at Stanford before and I agree there is a close similarity in the color and grain of the stones. I’ll keep digging.
Your best guess on the pylons matches mine. Cursory searching shows that someone associated with the Oakland Museum was interested in the original shoreline in the year 1800:
http://www.museumca.org/creeks/1180-OBOakHistOak.html
But it seems peculiar to me that no trace of public ceremony or commemoration shows up anywhere obvious. I’m guessing that I’ll find some info if I do a line-by-line review of the Measure DD records, or the folks at Parks and Rec may know about them because they occasionally get vandalized and have to be repaired (or in some cases, not).
20 February 2015 at 10:19 am
Jeff, I know the stones you mean. Obviously they’re recycled from somewhere, perhaps a ruined church from the 1906 earthquake. They remind me strongly of the locally quarried stone used at Stanford University and elsewhere.
It’s conceivable that a builder ordered a few railcars worth of Midwestern sandstone for a specific project, but building stone is primarily a local business, with prices limited by transport costs. More likely they’d get Sierran granite or Colorado limestone or imported Italian marble.
About the pylons, I don’t know. My best guess is that they might represent the original shoreline of San Antonio Slough, the body of water that was transformed into Lake Merritt.
19 February 2015 at 10:24 am
Perhaps you can help me resolve two stone mysteries by the lake.
1. I haven’t been able to identify the source of the building stones used to create the big circle at Astro Park (and the small tot lot on Lake Shore Ave). I get as far as the landscape architect who did the parks, and I get the impression that he used some cut stones that had accumulated at the city corporation yard, but not much more than that. On Oaklandwiki someone “had heard” that they were imported from Midwest quarries, but I don’t know enough to tell by looking at the stones.
and
2. What are those stacked stone pylons with “1800” inscribed in their tops that form wavy paths by the Lake Chalet and then reappear between the lake and the library at the other end of the lake?
I’m going to plan a visit to the Parks and Rec department over the next month or two, but am not sure if that’ll help.