Archive for the ‘Old quarries’ Category

Anomalies of Sausal Creek: Dimond Canyon

14 October 2019

This is the second of four posts about the peculiarities of Sausal Creek, going from its headwaters to the Bay. Here I’ll address Dimond Canyon, the 2-kilometer segment between the Warren Freeway and the flats of Dimond Park. The steep walls of the canyon, which is several hundred feet deep, are entirely hard sandstone of the Franciscan Complex, part of the Piedmont block.

This is the same stone quarried for decades in Rockridge (the Bilger quarry) and the land that would later become Piedmont (the Blair quarries and the Davie Stadium quarry). In fact the Diamond Cañon Quarry was one of two here in the canyon. It’s now occupied by the Zion Lutheran Church, as seen here from across the canyon.

The quarry scar appears on this terrain map as a big round nick in the canyon wall next to Park Boulevard.

A while ago in this space I described Dimond Canyon as a classic water gap — a stream-cut gorge crossing a bedrock ridge that otherwise seems impenetrable.

Geology textbooks will tell you there are two ways for streams to make a water gap. In the first way, the stream was there first (an antecedent stream) and a ridge of resistant rocks rose up around it. In dynamic California, this is a straightforward explanation of our water gaps. In the second, the ridge was there first, inherent in ancient deformed rocks buried under younger strata, and the stream (a superposed stream) cut down to, then into it while stripping off the overlying material. That’s how they explain the Delaware Water Gap and other examples in the gentle Appalachians.

Dimond Canyon is actually a semi-classic water gap. Yes, the ridge it crosses must have risen while the stream was cutting down, but the story is complicated by the fact that the watershed upstream lies across the Hayward fault, and is constantly being moved to the right. This means the canyon has hosted streams from several different watersheds over the past million years or so.

Therefore the streams feeding Sausal Creek today could not have dug the canyon; some predecessor watershed did it. There must have been gaps and surges in the water (and sediments) flowing through this canyon. If we ran things backward a million years, what would it show? The exercise would be blurred by serious uncertainties, but the matter is not beyond all conjecture.

I beg your indulgence as I present some slides from my talk to the Friends of Sausal Creek last month. They’re Google Earth views looking west across the fault. Here’s today, with the fault trace shown in red.

The view may be a bit confusing as I rewind the motion on the fault at about 10 millimeters per year. The far side looks the same because we’re focusing on it while it moves leftward, toward San Leandro. For a long time, Sausal Creek has been carried past small watersheds that, like today’s, could not possibly have carved Dimond Canyon. But about a million years ago, Dimond Canyon would have lined up with the watershed of Arroyo Viejo.

This looks promising because the watershed (the part above the fault) is about twice the size of Sausal Creek’s, giving it roughly twice as much water and cutting power to match.

But to make the canyon, you have to have something pushing up the ridge while the stream across it keeps cutting its way down. There’s nothing obvious that would have been pushing up the bedrock ridge at this time.

Going back a bit further, though, we line up with the great big watershed of San Leandro Creek, a dozen times larger. This stream has plenty of cutting power, evident in the canyon it’s dug where the dam and reservoir sit.

And finally, we have a mechanism here for uplifting the ridge that Dimond Canyon cuts across. The hills of San Leandro consist of a large slab of gabbro so big and strong that it deflects the Hayward fault slightly. Back when the sandstone of Dimond Canyon was grinding past the gabbro of San Leandro, the jostling between these two bodies of rock, caught in a vice by the geometry of the fault (a restraining bend), would have pushed both sides upward because that’s the only way out of the vice. And all the while San Leandro Creek would have been cutting a nice deep water gap as that hard rock rose.

Eventually, inevitably, the fault carried the water gap out of reach, and ever since then Dimond Canyon has housed lesser creeks for episodes of a few hundred thousand years. Sausal Creek trickles down the canyon today not doing much to it, the shrunken tenant of a structure built by a mightier maker.

This story (and that’s all it is really) appeals to me because it would also explain the presence of the Fan — the swath of gold on the geologic map representing Pleistocene sediment.

I’ve always regarded it as a fossil alluvial fan because of its shape on the map, but maybe that’s accidental. Maybe it’s just a chunk of old East Bay land that was lifted along with the Piedmont block, or washed off of it afterward.

I first posted about the problem of Dimond Canyon more than 10 years ago. Takes a while to figure out some things.

On Pryal’s quarry

21 January 2019

As I find the time (or as the subject hijacks me, in this case), I sniff around for details of Oakland’s rock quarries. There are a good two dozen of them. One I’ve always been curious about first appears in 1868 in The Natural Wealth of California, by Titus Fey Cronise: “The quarry from which the stone used in erecting the Deaf and Dumb and Blind Asylum was obtained, is situated on Pryal’s ranch, about four miles from Oakland. The supply of this stone is exhaustless.”

First thing was to find Pryal’s ranch. Andrew Dewitt Pryal (1832–1907), universally known as “A. D.,” had a spread in Chabot Canyon, the valley of Temescal Creek below the Lake Temescal dam. It was a thriving nursery that Pryal had started back in 1853, on land just upstream from Vicente Peralta’s reserve. Here it is on the Henkenius map of 1888, which has the arc running across the middle representing four miles’ distance from City Hall. It also labels the streams; Harwood Creek is called Claremont Creek today.

That map isn’t lined up with true north, so let’s be more systematic. The next set of maps all cover the same area. Here it is on the Dingee map of 1884:

and in Google Maps today:

So the Pryal ranch was on First Street, now Chabot Road, in the bottomland now occupied by Clover Drive, Chabot Court, Patton Street and part of the Chabot Elementary School grounds. Can you see what caught my eye? It’s that excavation on the north side of Chabot Road east of the hill, or what looks like one. There are so many quarry pits around.

Here’s a photo of the old ranch from the 1897 book Athens of the Pacific:

and roughly the same shot today, from farther east and higher up at the end of Margarido Drive:

Pagoda Hill got its name from the eccentric mansion built on its crown by J. Ross Browne. The young eucalyptus grove was typical of the time; Californians had been planting various Australian species for many years. Later a subdivision of Browne’s land was named Eucalyptus Hill, and Eucalyptus Road runs through it. There even seem to be a few trees left from that grove.

Anyway, back to the quarry. The original Deaf Dumb and Blind academy was a gorgeous thing built of an excellent “blue granite” that unfortunately was all discarded after the school burned down in 1875 and was rebuilt with a different plan. All “blue granite” means in this context is a hard stone with visible grains and no lime. And now we can look at the geologic map of the Pagoda Hill area.

The hills are made of Franciscan melange, a body of mostly metamorphosed sandstone and shale (argillite) with various-sized lumps, or knockers, of things like basaltic lava (fg, for greenstone), chert (red blobs) and serpentine rock (blue).

Here’s what’s over there. At the top of Roslyn Court, right under the big “J”, is greenstone. It’s shot with calcite veins and would never be picked to build a structure.

On Roanoke Road, the street between the “m” and the red blob, there’s mostly hard sandstone of the type customarily called “blue rock” by local quarriers.

I concluded, from a close-up look at the contours of the land and the general lack of decent rock, that there was no quarry here. It would have been one of the largest quarries in the county, supporting decades of production, but there’s no record of such a thing. This was just your usual digging and grading for a housing development.

So where was Pryal’s quarry? On the south side of his property. I remembered a photo displayed during an Oakland Heritage Alliance walk in Chabot Canyon: a shot looking across the valley along the old train trestle, and on the bare hills opposite was the high, rugged face of the abandoned Berkeley Rock Company quarry. I did my best to reproduce that photo by standing on the old grade, next to the top of Reata Place, and looking southwest. The quarry scar, as I recall the old photo, was at upper center about where the heavy cable passes in front of a house and lamppost.

That’s the rock face on Broadway, between Brookside Avenue and the Margarido Stairs, where three new houses were inserted about 10 years ago.

California State Mining Bureau Bulletin 38, from 1906, says about Berkeley Rock’s operation: “The deposit is a much altered trap-rock, and is used for concrete, macadam, and gutter rock. The company produces about 250 yards a day.”

I conclude that Berkeley Rock was working a cut that Pryal had opened 30 years earlier. That Pryal’s quarry produced enough good rock for a large stone building was a lucky accident, because the melange zone is a plum-pudding of mixed rock types.

The Berkeley Rock quarry made news during its years of operation, which started in 1902. The quarry’s 10-acre site was in the way of the Broadway extension, and a lawsuit in 1905 established that the road would go through. On 18 July 1906, an unknown dastard booby-trapped the quarry’s main engine with a package of dynamite, gravely injuring Frederck Hoffman, the superintendent. They used to call such criminals dynamitards. Another dispute over the quality of the company’s stone led to gunfire later that year. The company continued in business, however, for a few more years until the Oakland and Antioch Railway established its right-of-way through the property in 1911 and the Broadway extension was finally pushed through in 1915.

The homes in the old quarry have some rocks lying around. More Franciscan “blue rock.”

This tale still leaves a mystery. Cronise’s book also contains this interesting passage: “In 1864, Mr. A. D. Pryal, owner of a large ranch about four miles east from Oakland, discovered a vein of auriferous quartz in the Contra Costa hills, which cross his lands. Some of the specimens from this vein were rich in free gold, and the mine opened under the name Temescal, paid well for a short time, but the dislocation of the strata, a little below the surface, rendered its further working unprofitable.”

Gold is otherwise absent in the East Bay, as far as I know.

The Dunn-Spring Quarry, north Berkeley

27 November 2017

Glendale-La Loma Park, a little ballfield/playground complex in the north Berkeley hills on La Loma Road, is a repurposed quarry that’s had a true Berkeley history. The original quarry, operated by J. J. Dunn, appears to date from 1892. John J. Dunn, a Canadian immigrant born in 1839, was a major contractor in California building roads and sewers starting in the 1870s. This is Dunn portrayed in 1896 in the Oakland Tribune.

In 1900 Dunn advertised the quarry for sale “on account of sickness,” and died of Bright’s disease (kidney failure) in St. Helena that June.

In 1904 the Dunn quarry was reopened by Louis Titus, former head of People’s Water Company, as part of the Spring Construction Company. Its dawn-to-dusk blasting operations infuriated local residents, who obliged it to shut down in 1909 by threatening the business-friendly city council with a recall campaign. The company made the gaslighting claim that they were not operating a quarry, even though the rock from the pit was being used for streets and homes in the Thousand Oaks tract, but were in fact building a reservoir for the People’s Water Company.

After its abandonment the Spring quarry became an attractive nuisance, drawing generations of youngsters to its steep sides and deep swimming hole. Even those who didn’t swim in the cold, murky groundwater must have enjoyed the view.

In 1950 an 11-year-old boy drowned, and the city fenced off the quarry. The city acquired more property around the site in 1957, and eventually it became what you see today.

Unfortunately I have found no details of the site’s geology, although Titus called it a basalt quarry. The geologic map shows the downhill side as basalt of the Moraga Formation and the uphill side as the conglomeratic Orinda Formation.

This is the basalt. The brownish streaks are slickensides — friction marks from faulted fractures.

Other volcanic rocks here include rhyolitic tuff, a minor component of the Moraga Formation. It’s distinguished by its light color and broken (brecciated) texture.

Superficially, it resembles the Northbrae Rhyolite that makes up Grotto Rock Park and its sister parks, but unlike that heroically strong stuff it degrades quickly when exposed at the surface.

At the foot of the cliff you’ll find pieces of this excellent conglomerate from the Orinda Formation.

But the fact that it has crumbled down the cliff and will fall apart in your hands means that the rock face would be treacherous climbing. The city should be more forthright in discouraging climbing here; instead they just say “check out the other Berkeley parks with rock features…” Stay off it, and if an earthquake strikes while you’re standing there, jump back fast.

Orinda’s 1204 Hill

30 October 2017

As far as I know this hill has no name, but it’s a highly visible part of Orinda. You pass it on Route 24 between the Wilder exit and downtown, as seen in this Google Maps perspective view. The USGS topo maps give it an elevation of 1204 feet, so I’ll call it 1204 Hill.

It’s part of San Pablo Ridge, but the west branch of San Pablo Creek cut a deep gorge through the ridge while it was being uplifted, forming a classic water gap. That’s clear to see in the 1915 topo map, made before anything significant was developed there.

During the mid-20th century, at least four quarry pits ate their way into this hill, one on the north side and the others on the south. Now it provides a bit of seclusion to the exclusive luxury Orinda Wilder development. I paid the hill two visits this month, and to me it offers seclusion from Orinda Wilder. Here it is, as seen across Wilder Valley last summer.

A fire road encircles the hill for your visiting convenience. It offers good views all around. This is looking north across 24 to grassy Eureka Peak along with wooded Vollmer Peak behind it. Both are also part of San Pablo Ridge.

And in the other direction is the last, southernmost lump of San Pablo Ridge, separated from 1204 Hill by another branch of San Pablo Creek.

Looking west, Route 24 approaches the wall of the Oakland Hills. Eureka Peak, at the right edge, and 1684 Hill on the left, part of Gudde Ridge, form the sides of Siesta Valley.

Both peaks are made of the same lava of the Moraga Formation. The formation is folded like a taco shell under Siesta Valley, a geological feature called a syncline, and hey why don’t we look at the geologic map now. This is the same area shown in the topo map.

“Tmb” is the basalt lava of the Moraga Formation — the taco shell — and “Tst,” the Siesta Formation, is the filling. That red line with the little arrows is the axis of the syncline. The light-yellow unit “Tms” is sedimentary rocks, also in the Moraga Formation, that were laid down between eruptions of lava. To the right of the black toothed line — the Moraga fault — the rocks are much younger and I won’t mention them again.

The quarries were excavating freshwater limestone from the Siesta Formation, used to produce cement and soil amendments, and basalt from the Moraga Formation, used for crushed rock. Here’s the lava.

Where lava flowed onto wet ground, the underlying clay got baked and the steam oxidized the lava, turning both materials red. It’s not always easy to tell what’s what.

There are bits of light-gray limestone here and there. You can tell by the way a drop of acid fizzes vigorously on it. I didn’t take a picture, but I did stop to shoot examples of mineralization in the lava. They might be copper compounds, or phosphates, or several other possibilities that aren’t easy to identify just by eyeballing.

There’s also a little conglomerate that looks for all the world like the Orinda Formation. It goes to show that a geologic map is a simplification of a wacky, complicated Earth. However, I don’t quite trust the stone because it’s loose, not a proper outcrop.

Climbing the hill from the fire road is a scramble. There are only subtle trails, the kind that deer make. But on top of the hill there’s the stubs of a former water tower, and a stone spiral with a little cairn at the center, the kind that locals make. And outcrops.

The last thing to mention is the quarry scar. It displays the structure of the Moraga Formation nicely.

But the exposures are unapproachable and dangerous.

I’m not sure what the developers plan to do with this hill. Probably nothing except watch it closely. The closest street to the quarry scar has home sites only on the far side of the road, and there’s a wide ditch between the road and the quarry that will catch falling rocks.

I’m gonna keep my eye on this interesting spot.