The Oakland shellmound

6 February 2023

One thing geologists have to do, in any city in the world, is to erase the human changes imposed on the ground so they can see the landscape beneath. Whenever I do that in Oakland, mentally removing the accumulation of 150 years of buildings and development since Horace Carpentier (boo! hiss!) came across the Bay and staked out his downtown grid, I envision a wide grassland and wildflower-covered hills, punctuated by thick stands of oaks near the Bay and a striking redwood grove around Redwood Peak: the Ohlone world.

The Ohlones didn’t do a lot of building or digging on their land, just a little bit here and there, like the ocher quarry up by Holy Names University. They may have scooped out swimming holes in the creeks near their sweathouses. They left grinding holes, from centuries of pounding acorns into meal, where the rock was good. But they did make one kind of big thing, they and their ancestors — shellmounds. Geologists, be warned: one of these might fool you.


Shellmound near Mill Valley, 1909 (source)

The name is undignified, but the shellmounds can be thought of as the local version of the tells in the Middle Eastern countries, the remains of successive mud-brick villages that dot the ancient floodplains of the Fertile Crescent. The shellmounds may have begun as refuse heaps at seasonal campsites where abundant seafood and other resources supported generations of feasts, but the larger ones came to serve as burying grounds and ceremonial sites of regional importance. They became sacred. There were thousands of shellmounds around the Bay. Oakland had some too.

When agents of the Spanish empire came, removing the Ohlones and taking the land, the shellmounds were no longer living destinations. Later, American settlers saw them as a raw resource and started to dig them up in the 1850s. The mounds had good soil. The shells were mined and burned for lime, or crushed for roadbeds. The bones were dumped; artifacts were taken for souvenirs by generations of kids and passers-by, to be lost or broken. Museums hoarded some collections. The subject is a bitter one for the Ohlones and other Indigenous peoples, who still live among us and deserve better.

Wood and Munro-Fraser’s history of Alameda County, published in 1883, noted: “At some remote period there had been Indian camps upon the northern bank of the San Antonio Creek, and the mounds, composed mainly of oyster-shells, are not yet entirely obliterated.” San Antonio Creek was the brackish inlet where the Oakland harbor is today; see it on the inset of the 1869 Sessions map.

On the point at the east end of the creek, a shellmound is shown on the main map. Halley’s history of Alameda County, published in 1876, made note of its presence in the 1850s: “Shell Mound, the residence of Captain E. F. Rodgers, at the head of the estuary, became noted as a nursery and for the excellence of its fruit orchard.”

It became a military site during the Civil War years (which may be when this place took on the name “Union Point”), but the mound survived to be recorded in 1889 when the land was being subdivided as the Shell Mound Tract, at the intersection of Livingston and Water Streets.

When Nels Nelson, a UC Berkeley archeologist, published his survey of the Bay area’s shellmounds in 1909, he noted several in Oakland.

The map isn’t entirely reliable at the scale of publication (or the scan preserved online), but he located the cluster of big ones at the mouth of Temescal Creek, known collectively as the Emeryville Shellmound. He noted three more that had once existed in the Elmhurst area and another at the mouth of Brooklyn Creek, directly beneath the O in “Oakland.” Perhaps that last one was really the Union Point shellmound.

Remarkably, that location, 1901 Livingston Street, is a city-owned parcel, a triangular gravel lot by railroad tracks that’s now leased to a construction firm.

Perhaps the Ohlones would take it back. They could make it a nice adjunct to Union Point Park, the Embarcadero Cove Marina collection of historic buildings, and the art workshops in this modest district.

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The Curran Quarry

23 January 2023

Maple Avenue, in the upper Dimond neighborhood, used to be called Quarry Street. It was an old county road that served at least two quarries, starting with the Fruit Vale White Cement Gravel quarry in the 1870s. The road entered a small valley that cut through the southern tail of the Piedmont crustal block and over a small saddle in the ridgetop to the quarry, which exploited the light-colored fault gouge along the Hayward fault. Here it is on the digital elevation map based on a lidar survey of the fault zone a few years back.

This post is about the second quarry, which has had various names over the years. Its old scar is in the center of the image.

It was opened by James O’Brien some time before 1883 and was known as the O’Brien quarry. Later, when John F. Curran took it over, it became the Curran quarry, but it was also called the Fruitvale Red Gravel quarry, probably to differentiate it from the nearby white gravel quarry. Curran, a Canadian-born resident who died in 1912 aged 72, owned land around present-day Curran Avenue.

Like nearly all Oakland quarries, it produced crushed rock. Some jobs, like roadbeds for trains and cars, demanded hard “blue rock,” but there was also a good market for crummier stuff, and that’s what was here. Being so near the fault, the rock was pervasively shattered, which left it open to weathering and alteration. The area is mapped as mixed Franciscan rocks, which doesn’t tell us much because “Franciscan” is a grab-bag term.


Qpoaf is really old gravel, KJf is undivided Franciscan rocks, and Jsv is Leona volcanics. Find it on the main geologic map toward the middle.

In 1904, the county was asked to give Quarry Street the more appealing name of Maple Avenue. (At that time Oakland had not yet annexed it.) Later that year the owner of the 22-acre parcel the quarry sat on offered the “Crescent View Tract” to the county for use as a hospital, but nothing came of it. The state mineralogist took note of the Curran Quarry in 1906: “The rock is termed ‘red cement gravel,’ and is a very much altered rock, recemented by a red clay. Used as a top dressing for roads and walks.”

The area got annexed in 1909 and developed by the 1920s, but the quarry pit was abandoned at an unknown date and sat vacant until after World War II. It’s visible at the top of this photo from the winter of 1945, at which time the city owned it.


Original photo from Oakwiki

The pit was subdivided and filled with homes over the following decade, and today it looks like anywhere else up there.

The house on the corner has a wonderful exposure of serpentinite that deserves its own post some time.

From the street, everything looks green and lush and fine. From across the valley, though, there are spots visible where that “red cement gravel” has been freshly exposed by our recent hard rains.

Quarry pits are wounds to the land that Earth tries to heal.

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Oakland stone landmarks: The McElroy Fountain revisited

9 January 2023

I made a brief post about this fountain a few years ago — it was the first “Oakland stone landmark” post — but a reader’s question pushed me all the way into a worthy rabbit hole.

When John E. McElroy died unexpectedly on 24 March 1909 at less than forty years of age, the city of Oakland mourned a public benefactor whose unborn child would never know him. As the City Attorney, McElroy wrested back Oakland’s waterfront lands from the railroad, undoing one of the great crimes of our founder, the scoundrel Horace Carpentier. He also helped establish our reputation as a legitimate City Beautiful in a way that went beyond grand boulevards and splendid public buildings: children’s playgrounds. He was elected four times; the last time both the Democrats and the Republicans endorsed him.

Park Commissioner James Edoff, a close collaborator and friend, launched a private donation drive to honor McElroy’s memory with a large fountain in Lakeside Park. The design, by Park Commission architect Walter Reed, was submitted in March 1910. A scale model was put on display 7 July 1910, and the Tribune reported, “Granite, marble and concrete are up for the consideration of the commission and as soon as the decision is made and the funds which the city will contribute towards its erection are turned over to the commission the work will begin. It is thought that the commission will decide in favor of the use of granite in the construction.”

Bids came in that August from six companies, including the Raymond Company (whose Sierra White granite clads City Hall) and California Granite Company, and the Colusa Sandstone Company won the job. The city chipped in the majority of the $15,000 needed.

I suspect that the bids fell into two categories: the granite companies could supply their own stone while the other firms could emphasize their skills and connections.

Colusa Sandstone Company was a very successful firm whose quarries, just east of Sites and still visible today, supplied the stone and stoneworkers for some of San Francisco’s finest Belle Epoque landmarks: the Ferry Building, the Emporium Building, the Kohl Building, the Spreckels Building and more. They could arrange for premium stone from the best sources and finish it to the highest state of artisanship.

That October the Tribune reported, “The basin and other portions of the fountain will be of white marble, for which the city has provided.” Specifically, as other stories reported, it was Georgia marble.

“Georgia marble” was effectively a trademark at the time. Then and today, this stone comes exclusively from Pickens County in northwestern Georgia, west of the former gold rush town of Dahlonega and home of an annual marble festival. The Georgia Geologic Survey described the rock and the marble industry as of 1907, when the state was second only to Vermont in the value of its output. Many buildings in Washington DC use Georgia marble. The statue of Lincoln in the Lincoln Memorial sits on stone identical to the McElroy Fountain.

All the evidence points to the Georgia Marble Company’s Cherokee Quarry, located east of Tate, which at the time supplied a coarse-grained stone of white or “clouded” color with light blue-gray bands. See some of it at the historic Tate mansion on the quarry grounds.

Marble is what happens to limestone when it’s buried and subjected to the pressure and heat found several miles underground. Old geologic reports assign this marble an Early Cambrian age, making it a good half-billion years old. It was originally a body of limestone that collected on the floor of the Iapetus Ocean, which resembled today’s Atlantic in being the result of continental rifting. The metamorphism that turned this stone to marble happened later, in Ordovician time, when plate tectonics forced the coasts of the Iapetus Ocean back together. This continental collision wrinkled and folded the rocks at the heart of the Appalachian Mountains, in the inner Piedmont and Blue Ridge belts.

The bluish streaks are considered to be remnants of bedding in the original limestone. They have a little magnesium in them and a touch of iron.

Cherokee Quarry marble is exceptionally pure and notably coarse grained, both of which account for its strength and endurance.

Now that I know more about this distinctive stone, I expect to recognize it everywhere.

In June of 1911 bids were received on the tiling and mosaic work: “The marble tiling and mosaic work will be one of the most beautiful portions of the fountain. Of four colors of imported marble, the stone will be wrought into designs at the entrances in consonance with the rest of the fountain.” Marbles to be used in the tiling and mosaic are green Verdi antique, white Alaska, or heavily veined Italian, red Numidian, yellow light Sienna and nemesis marble.” (Visit the Getty Museum’s online thesaurus for more on some of these.)

Work on the mosaic was still in progress when the Park Commission formally accepted the fountain on 6 July 1911, only 16 months after McElroy’s death. The fountain was dedicated on 17 September 1911, in an elaborate ceremony attended by thousands. After a series of speeches and musical selections, McElroy’s little boy, John Jr., turned the fountain on. Then Scott’s Band played “The Stars and Stripes Forever,” followed by “America” with the crowd singing along.

Even the water is special. The fountain lies on top of a reservoir that serves the Lakeside Park grounds. It was once (and may still be) fed with groundwater from two wells nearby, perhaps in one of those nondescript little huts in the park.

The 11 years since my previous post have not been kind to this exceptional structure.

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