Finding Fossils in Facing Stones
Greetings Blogophiles! It’s been a long winter and a very wet spring, neither of which have been particularly conducive to going out into the field to find fossils. What’s a paleontologist to do? I suppose one could just wander the museum, camp out in the collections, or follow #FossilFriday on Twitter to see all the fossils one wants, but that kind of takes the sport out of it. One of the joys of being a paleontologist is getting to go look for fossils that haven’t been found before. Fortunately, thanks to some fortuitous foresight on someone’s part one needs only to step outside the Main Museum (NEC) to find fossils. Yep! You..yes…You, can find fossils in facing stones! Crinoids, corals, bryozoans and even cool trace fossils are all there if you choose to look for them. Here’s how, what, and why.
All that non-descript grey rock surrounding Bicentennial Plaza that perhaps you’ve sat on to eat lunch or you’ve seen kids running on is actually Indiana Limestone, a Paleozoic marine limestone. It’s not pretty like all the granite on the exterior of the building but it does have fossils, lots of fossils, look closely. The Indiana Limestone or more technically the Salem Limestone was deposited as a result of millions of years of marine fossils decomposing at the bottom of a shallow inland sea during the Carboniferous Period. This limestone has been used for the exterior of the Biltmore Estate, the Empire State Building, the Pentagon and many other famous buildings and landmarks. Overtime, thanks to weathering and staining by lichens, the fossils contained within the limestone become more and more apparent. Let’s have a look shall we?
Oh look! Crinoids! I like crinoids, though they’re small, (~0.5 cm in diameter) these disk –like objects are actually columnals from crinoids’ stems. Crinoids, also known as sea lilies, are actually marine animals. Crinoids are still around in shallow seas today, but were also prevalent during the Paleozoic.
The largest and most interesting fossil I found on the plaza outside the Museum is a trace fossil. This trace is approximately one meter long and after much debate by the ichnologist (people who study traces) group on Facebook (yes, there is such a group and yes, surprisingly, they often have interesting discussions and can be very helpful to those of us, like me, who know very little about trace fossils), the majority opinion is this trace is probably Parataenidium. Parataenidium is a back-filled tubular burrow and is a good indicator of Carboniferous sediments. Normally one would find this type of burrow parallel to the bedding plane surface, but as the limestone has been slabbed and mounted vertically, one gets a different perspective on this fossil. Unfortunately, the organism that made this trace isn’t currently known or I’d tell you about it too.
There are other fossils to be found just outside the museum if you’re willing to take the time to look for them. I’ve seen cross-sections of snails and bivalve shells in the rocks surrounding the Rachel Carson Garden (also Salem Limestone), and other fossils. Next time you visit the Museum, why not try to find some fossils outside it first. Remember you can’t collect them without getting arrested, but you can take as many pictures as you’d like.