Comments for Oakland Geology

Comment on Driveway of delight by Sheldon White

Sheldon White — Mon, 30 Nov 2009 17:26:04 +0000

I see some of the little chalcedony nodules from the Sibley Quarry in there! And the Actinolite was probably from Wildcat Creek or Ring Mountain.

Comment on Oakland from the air by kelly

kelly — Tue, 24 Nov 2009 18:59:15 +0000

If you post that photo of the airship you could win a flight also if you sign up for their last minute deals and can make it last minute it’s a bit more affordable good luck

http://www.airshipventures.com/tracking-sightings.php

Comment on Oakland from the air by Mike Hardy

Mike Hardy — Mon, 23 Nov 2009 20:29:49 +0000

I know! Every time I see that thing float by I want to hop on it. Previously I was thinking the Sausalito seaplane would be fun, but I think the airship would beat it on many levels. One of these days…

Comment on Treasure! by Dan L

Dan L — Sat, 21 Nov 2009 17:23:57 +0000

Any chance of a photo of that red chert? I would rather see it as an illustration for your excellent blog than a heavy-load dumpster full of grayish stuff :-) [Well, there's here and here.]

Comment on Rocks of Leona Quarry Con’d. by Andrew

Andrew — Mon, 09 Nov 2009 18:48:03 +0000

That shows how parochial I am. I haven’t gotten around to visiting the Briones Formation. Looks like it will be fun.

Comment on Rocks of Leona Quarry Con’d. by P J Evans

P J Evans — Mon, 09 Nov 2009 05:08:15 +0000

I found a small rock like that along Arroyo del Valle, south of Livermore, in the 1960s. (Don’t know where it is now; I’ve moved enough times that it probably got left behind somewhere.)
It had some recognizable turret shell bits, including one lengthwise cross-section, but was mostly just shell hash.

Comment on Rocks of Leona Quarry Con’d. by Jacob Lee Fink

Jacob Lee Fink — Mon, 09 Nov 2009 04:31:21 +0000

Those rocks with the shells in the gray sandstone/siltstone are locally known as Briones Formation. Indeed shallow marine environment. They can be seen all around peaks about the East Bay. I have seen similar rocks at Mission Peak in Fremont and around the Norris Canyon area between San Ramon and Castro Valley.

Comment on Rocks of Leona Quarry Con’d. by Andrew

Andrew — Mon, 09 Nov 2009 01:55:07 +0000

Las Trampas–that would be over the hills. It’s been on my list of places to visit for years.

But these rocks aren’t the kind you would get from a landscaping company, I don’t think. They struck me as the kind of rocks a big homebuilding contractor might have lying around from another project, like one in Tracy or, as you suggest, in the San Ramon Valley.

Comment on Rocks of Leona Quarry Con’d. by Jef Poskanzer

Jef Poskanzer — Sun, 08 Nov 2009 20:04:26 +0000

Cool. Las Trampas has a bunch of these, are there any quarries near there?

Comment on The Rocks of Leona Quarry by Andrew

Andrew — Sun, 08 Nov 2009 00:29:35 +0000

I've been doing some reading about the Coast Range Ophiolite, of which the Leona Quarry rocks are a part. The most recent work I've seen considers this rock not a lava, but a highly compressed and altered tuff, that is, the ash and rubble erupted from volcanoes. So the little flat features in the last photo would be the remnants of lapilli: pebble-size particles, like bits of pumice or lava, that are now almost erased. It's thought to be about 150 million years old, unlike the far younger volcanic rocks of Sibley volcano.