I was digging a trench in my garden for a French drain when I came across a rather large collection of fossilized shells. Any idea about their species, approximate age and whether they are native to my area of Troutdale? They were found about 1½ feet below the surface, and they were surrounded by a sandy/sandstone mix that looks high in iron. I’m curious if they are freshwater species because I heard from a neighbor that a creek used to run through our backyards.
What an amazing find! These fossils are considerably older than the creek that used to flow through your backyard. The fossil shells appear to be marine. There are a couple of possible scenarios for how they arrived. They could be bedrock, deposited there in the geologic past or had help in their transport, coming from marine deposits on the coast.