I asked my newsletter subscribers for pictures of concretions, and now there are enough to fill this new gallery of concretions. These intriguing objects are often taken for fossils, but they form purely from mineral deposition in newly buried sediment that is just beginning to become rock—that is, they arise during early diagenesis. Millions of years later, they erode out of their matrix and in some places they make impressive spectacles.Bowling Ball Beach — Courtesy Chris de Rham under Creative Commons license
Comments
Hi Mr. Alden,
I have a large collection of photos of the Coastside’s many concretions. Dumbbells, cannon balls, shmoon, Swiss-cheesed, in situ, our local Cannonball Beach, etc. I’d be glad to add them to your collection. If interested, please contact me.
I am actually trying to contact you about a posting on Pebble Beach you wrote, that a friend sent the link to. I think you’d be interested in what happens when thereabouts, the longshore current interacts with the PPF’s underwater surface’s differential erosion of the layered turbidite flows. It’s been my obsession for years. Enjoy. John