Friday, April 26, 2013

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.

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


  1. I am a PUC employee who has hiked around the Sunol Valley since the late sixties and have found examples of the finds described here numerous times, examples of which include riverworn cobblestones from the ancestral Sierra Nevada mountains from which some of our local hills are made of entirely. Also there are some side canyons to the watersheds of Alameda Creek and Arroyo Hondo that are composed entirely of seashell 'trash' fossils, but perhaps most interesting is the geologic evidence of ancient earth movements in this most active of earthquake zones, the most prominent of which is the canyon area where the Arroyo Hondo joins Alameda Creek. We live and work in one of the most facinating areas of our planets crust, and it is gratifying to see the care taken by the PUC in the reconstruction of the Calaveras Dam project.

    1. What are these "trash fossils" that you speak of? Are they imbedded in sandstone, like the picture above, or are they like loose shells in the sand?