Archive for the ‘oakland fossils’ Category

The fossil treasury of UCMP

18 May 2015

Last month, as part of Cal Day, they were giving backstage tours at the UC Museum of Paleontology. The day is a mob scene, but on the last tour of the afternoon I had a fine time being shown around by two of the museum’s scientists.

The collection is vast, the world’s largest university collection. Only part of it is in the Valley Life Science building. There’s also a building in Richmond, and there are great accumulations of tar-seep fossils (from La Brea and McKittrick) housed in Sather Tower—the Campanile—because they smelled too much to keep with the others.

The collection at Valley Life Sciences is housed in huge cabinets that slide along tracks to open enough space to pull out the drawers. Many of those drawers are full of microfossils.

UCMPmicros

These are a huge part of California’s heritage. It was a thorough knowledge of microfossils in the rocks of the Central Valley and Southern California that informed and guided our petroleum industry. California remains America’s fourth-largest oil and gas producing state thanks to this scientific-industrial heritage.

But naturally, the museum had some of their photogenic specimens out. This Triceratops horn, with slices sawn off to expose its interior, was a privilege to hold. Unfortunately, the Bay area has no dinosaur fossils at all, although a few marine vertebrates from Mesozoic times have been found.

triceratop-horn

This ammonoid shell was interesting because it has a beautiful set of tooth marks on it, courtesy of a mosasaur. In the corner of the photo is a drawing of the specimen, as published in a scholarly paper.

mosa-chomp

Mosasaur fossils, to my knowledge, are not known from California either. Not yet, anyway.

And this thing sitting on the floor gave me joy. It’s a stump from the world’s first forest, dug up in rocks of Middle Devonian age in upstate New York.

psaronius-erianus

The inscription reads, “Psaronius Erianus Dawson / [Hamilton Group] Tree Fern / GILBOA, Schoharie Co. NY.” The Gilboa forest was first excavated in the 1870s. When I was on About.com, I featured Gilboa in my list of geo-attractions of New York state, and I hope you’ll seek it out if you’re ever there.

This specimen was undoubtedly part of an exchange of fossils between UC Berkeley and the State Museum of New York, a traditional way for paleontologists to enrich each other’s collections. It was surely a source of pride for Joseph Le Conte, the geologist who was the University of California’s first president. His fossil collection was the nucleus of today’s museum.

Wood fossil

22 March 2013

I was lucky enough to examine this large specimen of fossil wood that I was told came from the hills of San Leandro.

SLfossilwood

People have told me about and showed me pieces of fossil wood from the East Bay hills before. I’m no expert on the subject, and I haven’t done a lot of fossil hunting in Oakland. But we have young terrestrial rocks around here in addition to the abundant marine rocks—primarily the Orinda Formation, of Miocene age. I assume this came from there.

People have told me about fossil wood in Wildcat Canyon, but that’s regional park land where collecting is forbidden. This specimen, I was told, was from EBMUD land, where collecting is not expressly forbidden, although I assume that vertebrate fossils (animal bones) are protected. I have purchased an EBMUD permit and have been looking forward to using it for responsible geologizing.

Smilodon californicus

15 February 2013

If you’re at UC Berkeley with a little time to spare, go visit the Valley Life Sciences building and say hi to the sabertooth cat fossil there.

smilodon

Smilodon californicus is our official state fossil. It got the honor from its abundance in the tar pits of Rancho La Brea down in Los Angeles. It turns out that they were suckers, walking into the tar to feed on animals already stuck there, then getting trapped themselves. They and the extinct dire wolf are the two most common species in the tar pits.

Presumably they lived in Oakland, but I don’t see any reference to local Smilodon fossils. One of the things on my to-do list is to visit the paleo people at UC Berkeley and learn more.

Mammoths in Oakland

16 December 2012

The skull of a Pleistocene mammoth appears on this building at Telegraph and Sycamore.

mammothsycamore

Oakland’s youngest rocks are Miocene in age, around 10 million years. Next in age come the gravels and sands of Pleistocene time, within the last 2 million years or so. (I’m vague about this number because the definition of the Pleistocene just changed, and because I don’t know any firm dates for these sediments.) Any material from the time in between either was erased by erosion or never existed.

Because the great glaciers sucked more than 200 feet of water out of the ocean, Ice Age Oakland was part of an enormous grassland that extended across today’s Bay and far west of today’s coastline. State Parks paleontologist Breck Parkman has called it a California Serengetti (sic), teeming with large herbivores and predators to match, all of them extinct today except the condor.

Remains of these animals have been found in Oakland. When the Alameda Tube was being dug, fossils of ground sloths, short-faced bears, mammoths, camels and bison were recovered. Mammoth remains have been found in the Harris Street Tunnel, Montclair Playground, and 81st Avenue. A Pleistocene horse was found at Oak Knoll Hospital. A ground sloth was found at the Coliseum. When the next large-scale excavations happen in Oakland, the diggers may find these as well as fossils of dire wolves, mastodons, deer, llamas, pronghorns and smaller ground-dwelling mammals.

Rocks of the Caldecott Tunnel

23 November 2012

I mentioned a few posts back that I would be doing a field trip related to the new bore of the Caldecott Tunnel. Here’s how it went.

We (the members of the Northern California Geological Society) started with a talk at the Caltrans headquarters in Lafayette. They showed us historical photos and engineering diagrams, explained the New Austrian boring technique, and ascertained that we weren’t interested in a “photo opp” near the tunnel entrance. Apparently that last is a prime demand of many tour groups, but we didn’t care.

First stop was at the old tunnel entrance, which I’ve shown here before. The old plaque has been refurbished and looks garish now.

old tunnel

The tour leader unfurled a huge geologic map of the tunnel and talked a lot about all the rocks (click the image to see the 1000-pixel version). I studied it closely, because it’s the best we have for this part of town.

tunnel geologic map

The blue stripes on the west side of the map are the Sobrante Formation, the green, purple and tan stripes are the Clarement Shale, and the buff stripe on the right is the Orinda Formation. These are stacked up in order of age, old on the east, and tilted nearly straight upright.

Next we wound our way around to the extreme top of Broadway, next to the tunnel’s west entrance. Here’s the view from there looking north.

The rocks in the immediate area are in the putative Sobrante Formation, but the Claremont formation takes over just to the east (right). Here’s the Sobrante exposed at that spot.

sobrante formation

It’s pretty crummy rock, and the tunneling was quite slow there. Every couple of meters, the tunnelers drilled a fan of holes over the roof of the upcoming dig segment, each one reinforced and grouted. That reinforcement allowed the tunnel roof to stay up long enough to spray it with shotcrete, which in turn held up the roof until the real concrete tunnel lining could be emplaced. The tunnel’s final shaft is round, as strong as an eggshell in its resistance to the earth’s weight. (To see what I mean, try gripping a raw egg firmly in one hand, fingers on all sides, and attempt to crush it. You can’t do it.)

Next we visited the type locality of the Claremont Shale, where I learned something new about it.

claremont shale

The unit here is mostly thin beds of chert and thinner interbeds of shale, but there are also lumpy beds in it—see one running down the center and another one near the right edge. Those are dolomite. It turns out that carbonate and silicate minerals dislike each other enough that they tend to segregate themselves: in chalks, you get flint lumps, and in cherts (as here) you get limerock lumps.

Our last stop was on Fish Ranch Road just east of the tunnel, where we looked at the Orinda Formation in the surrounding hillsides. The Caltrans people brought along a box of the fossils recovered from the fourth-bore project, so I got to lay my hands on this Miocene horse tooth . . .

horse tooth fossil

. . . and this slab of fossil leaves.

leaf fossils

The Caltrans public-information official was at obvious pains to say how happy the paleontology contractors were and how well the fossil collecting had gone. Obvious to me, anyway. I won’t forget the complaints I heard from the other party, but I will keep in mind that most stories have at least two sides, and that every fossil preserved is a victory over the universal decay of the world.


Follow

Get every new post delivered to your Inbox.

Join 8,796 other followers