What is a desmostylus and what is it doing in the Sunol Valley?

Photo courtesy of www.alchetron.com

A Desmostylus was a hippo-like creature that lived about 20 million years ago. It happens to be the only order of marine mammal to have gone extinct. Some individuals lived along the shoreline of an ancient ocean that used to be located where the Sunol Valley is today.

If you stumbled upon this would you know it was a rib cage?  What it looked like prior to Excavation

During excavation of the Calaveras Dam Replacement Project, the project paleontologists found not only a few teeth belonging to these strange creatures, but recently found an entire rib cage. Removing the fossilized rib cage of an animal that likely weighed between 200 and 400 pounds in life is no small task.

First the bone had to be cleaned and separated as much as possible from the surrounding rock on the hillside.

Above is the picture after our fossil was cleaned and ready to be removed.

In order to physically remove it from the hillside, crews used a lift to grab the entire rib cage. Now that the rib cage has been safely removed from the construction site, it awaits further stabilization treatment by project paleontologists. 

See you around the Valley!

Calaveras Dam in the News

Just last week, we were able to share our story about recent fossil finds here at the Calaveras Dam Replacement Project.  As our crews are busy working on major spillway work and grouting operations for the new replacement dam, we were able to take a moment to highlight the interesting fossil finds out here.

Check out the story here from the San Jose Mercury News: Fossils Found at Calaveras Dam

The Calaveras Dam Replacement Project is the largest project of the Water System Improvement Program (WSIP) to repair, replace and seismically upgrade key components of the Hetch Hetchy Regional Water System.

For more information, please contact us at mle@sfwater.org

Whales in the Sunol Valley?

Since construction began at the Calaveras Dam, team paleontologists have had some remarkable finds from ancient shark teeth to marine mammal vertebrae all collected during the excavation of over 4 million cubic yards of earth over the sediments that were once an ancient sea floor.  

Just this week, project paleontologists found a portion of an ancient whale skull in the slope above the spillway excavation of the new dam. The skull is almost a yard long and relatively intact, except for a small portion of the right rear section which is missing. Our paleontologists are still researching the find but initially assess the fossil to belong to a Mysticete (or baleen) whale, from the family of Humpback, Grey or Blue whales that live in the oceans today and forage on plankton. This fossil was discovered in the temblor sandstone formation which makes it over 20 million years old.

The project takes important steps to salvage these paleontological finds for educational purposes. The critical construction work to build a replacement dam has not been affected and continues, while we discover amazing fossils to add to the rich history of this valley.

Paleontologists Bruce Hanson and Jim Walker work on uncovering fossils at Calaveras Dam. Photo credit: Robin Scheswohl

In November 2013, a collection of bones including vertebra from a marine mammal were discovered on the lower portion of the Spillway.  It appears to show a complete cross section of the body, neural arch and measures 15 x 7 centimeters. Some of the other bones appear to be ribs. None of the specimens found interfered with construction activities and the specimen still remains in the rock.

Fascinating Fossil Finds at Calaveras Dam

Every day, our scrapers dig soils and earthen materials to make room to build the replacement Calaveras Dam.  We have special staff who monitor high sensitivity areas during construction searching for paleontological and cultural resources, which are protected by federal and state laws.  Construction crews also attend environmental training about the identification and protection of paleontological and cultural resources. Calaveras Dam project teams have discovered fascinating finds within our construction site. 

What are Paleontological Resources?

Paleontological resources include: remains of prehistoric/extinct plants and animals, petrified wood, fossil leaves, fossil remains of vertebrate and invertebrate organisms, fossil tracks and track ways, and plant fossils, typically of Pleistocene Epoch (> 12,000 years ago) or greater age. 

What have we found?

Fossilized plants such as wood, leaves, and a pine cone have been salvaged from the site.  Invertebrates uncovered include: scallops, clams, snails, barnacles and worms.  We have also found shark teeth that are still being analyzed but may be related to a great white shark although much larger (Think “Jaws” and then some).

Our most fascinating finds are linked to prehistoric marine mammal(s).  This includes an intact portion of a backbone of a whale.  These finds are still being analyzed by experts.

Why?

Most of the fossils have been found in the 20 million year old marine sandstone called the Temblor Formation.  The Sunol Valley area was below sea level in the Pacific Ocean about 20 million years ago and has since been uplifted along with the rest of the Coast Ranges. Life along the old coast was similar to today, with abundant clams, mussels, sea worms and other invertebrate organisms living in the sand. But the fossils also document significant differences from today’s relatives and provide important information about the details of evolution and environments of the plants and animals represented by the fossils.  We continue to work to preserve and protect these neat findings every day.

Fossils & Shark Teeth discovered at the Calaveras Dam Replacement Project Site