From the Depths
In my day job, I am a hydrogeologist. I work for a consulting firm in Tacoma, Washington. We put in a lot of drinking water wells throughout Washington State. On a recent well drilling project for the City of Sumner, we found something rather unusual – deposits from an ancient beach at a depth of 464 feet below land surface (several hundred feet below sea level). One of my colleagues will be discussing these deposits at the Washington State Hydrogeologic Symposium, which is being held this week in Tacoma. For his presentation, he asked me to take some photographs of one of the shells and some wood found in these beach deposits. Those photographs are included here.
We really don’t know how old these beach deposits are. The shells and wood found were not old enough to be fossilized. They are still fairly fresh looking. In fact, our field geologist reported the drill cuttings with the shells smelled like the beach when they were brought to the surface. Our best guess is that they are somewhere between 5,000 and 100,000 years old. We may eventually get a date from the wood using carbon 14 dating, but have not done so yet. Besides scallop and clam shells, there were also barnacle shells in the drill cuttings.
This particular well was drilled with cable-tool methods. Cable-tool drill rigs essentially pound a steel casing into the ground, than remove the sediments in the casing by sucking them out with a bailer (basically a steel tube with a one-way valve on the bottom). If the sediments aren’t loose enough to be picked up by the bailer, a drill bit (basically a large hunk of steel) pounds the sediments into a slurry so they can be more easily picked up. Considering this drilling method, it is very surprising that one of the shells came up intact – most were quite broken.
Photography wise, I took these images several days ago in my studio with a table top setup using a single monolight on one side of the table, a reflector on the other, and black or white matboard as a background.