|Panopea abrupt (Conrad, 1894)|
This fossil specimen was collected from lower Miocene deposits in the Clallam Formation on the foreshore bordering the Strait of Juan de Fuca near Clallam Bay, Olympic Peninsula, northwestern Washington. The oldest recorded specimen of one of their modern relatives lived not too far from here in the Strait of Juan de Fuca. That lovely was an impressive 168 years old.
A geoduck sucks water containing plankton down through its long siphon, filters this for food and ejects its refuse out through a separate hole in the siphon. Adult geoducks have few natural predators, which may also contribute to their longevity.
In Alaska, sea otters and dogfish have proved capable of dislodging geoducks; starfish also attack and feed on the exposed geoduck siphon.
Clallam Bay is a sleepy little town on the northwestern edge of the Olympic Peninsula. It was founded back in the 1880s as a steamboat stop and later served as a Mill town. If you are planning to visit the fossil exposures, head to the edge of town where it meets the sea.
Once at the water's edge, head east along the shore until you can go no further. You'll find marine fossils in the sandstone on the shore and cliffs. Mind the tide as access to the fossil site is only possible at low or mid-tide. You'll have to swim for it if you time it poorly. Clallam Bay: 48°15′17″N 124°15′30″W.
Near this site, there are many additional fossil localities to explore. In Sequim Bay, you can find Pleistocene vertebrates as well as Miocene cetacean bones near Slip Point. Near the Twin Post Office, you can find Oligocene nautiloids and bivalves (2.5km west in the bluff); You can find crabs including, Branchioplax in the Eocene limestone concretions from Neah Bay.
References: Addicott, Warren. Molluscan paleontology of the lower Miocene Clallam Formation, northwestern Washington, Geological Survey Paper 976.