San Diego Natural History Museum paleontologist Rodney Hubscher holds a bed of mussels and a scallop shell taken from the hillside along state Route 15 north of Adams Avenue, March 15, 2016. | Photo Credit: Megan Burks, KPBS
A small whale bone sticking out from a sandstone bluff alerted Caltrans crews working on a bikeway along state Route 15 that something very different once passed through there.
Caltrans called San Diego Natural History Museum paleontologist Rodney Hubscher to the site. He said the small fragment is from the fin of a whale that swam through the area 3.5 million years ago.
Bands of mussel and scallop shells stripe the hillside higher up.
Hubscher said much of the region was underwater before the earth cooled, lowering sea levels, and shifts in tectonic plates jutted landmasses.
“It is very rich in fossils. Whenever you cut into the San Diego Formation, there’s a pretty good chance you’re going to find fossils,” he said. Similar fossils are currently being found at a bikeway construction site along Interstate 5 at Genesee Avenue.
Lauren Kemp of Caltrans works with the Nat to preserve fossils found at job sites throughout San Diego and Imperial Counties. She said they often resemble those she finds on the beach while camping in Baja along the Sea of Cortez.
“The same shells we find on the beach that are still live, we find them here 1½ to 5 million years old,” Kemp said. “So it’s incredible to look at the difference in time.”
Some of the findings will go in the Nat’s collection. But Kemp said Caltrans intends to preserve the hillside, making a quick bike trip a trip through history, too.
The bikeway is expected to open in late 2017. It will be a raised path along state Route 15 connecting Kensington and Mission Valley. The second phase of the project will extend the bike route south to City Heights.