I couldn't resist adding a few more shots — this time also with higher res — of the results of the fossil hunting expedition. It still boggles my mind that these shells are over 70 million years old. The geologic and environmental changes that the Earth has endured over that time and beforehand are truly amazing. (For a fascinating read on that, by the way, may I recommend Robert M. Hazen's The Story of Earth: The First 4.5 Billion Years, from Stardust to Planet — from everything to the colossal collision that created the moon to the "rusting" oceans, it's pretty cool.) The boring holes in most of the shells are particularly interesting because they are so evident and meticulous in their spacing. In picture 4, you can also — I believe, given the descriptions Poricy Park provided — see the imprint of the worm-like creature that created it. And picture 3 is a good illustration of how shells are created in layers. (You can read about that process over at Scientific American.)
I've been wanting to go fossil-hunting for years, even before I had children. We had a chance to do so this past summer at the Poricy Park Conservancy in Middletown, NJ. The cool thing about Jersey — yes, I know what you're thinking — "there are cool things about Jersey?" — is that back in the Cretaceous (around 140 to 65 million years ago) what is now Jersey and the northeast was a shallow inland ocean. Take a look at what North America looked like around that time at the Paleontology Portal.
Most of the fossils found at the Poricy Brook Fossil Beds are shells though shark teeth have been found. Dinosaur fossils are rare but according to their literature have also been found.
We found the shells you see above. They include choristothyris plicata, which is a small brachiopod — they're the smaller clam-like shells you see above. The shells with the holes are from boring sponges — not as in "un-interesting" but as in invertebrates that dug through the shells. The trip was a great time — the Poricy Fossil Beds are easily accessible from the road and the Conservancy rents trowels and sifters for digging in the stream bed. It's amazing to wade along the stream bed and realize that you're looking for the remains of animals that were around 72 million years ago. It's so hard to wrap your mind (at least my mind) around a century or a thousand years and the change those years can produce, that to imagine a million, never mind 72 million years ago, before the extinction of T-rex (!) is mind-boggling. As the Poricy site states, the digging at the site is made possible by the Poricy Brook's cutting action, which exposes the Navesink Formation, the layer of rock which contains the ancient remains of prehistoric clams and mussels. I highly recommend the trip — our 2 year old and 5 year old both found it fun. The former more because it was digging in (for her) shin-deep water and mud, and the latter for the same reasons and for the opportunity to dig up items that once shared the same space (so to speak) with the mighty dinos.