Tuesday, February 16, 2016

The Impermanence of Being (a Fossil)

A fossil you find may have existed hidden away underground for millions of years, but they have a very short lifespan once uncovered and exposed to the elements. Rain, snow, wind, animals, plants, and people (not just collectors) all wear away at exposed fossils that are almost invariably fragile. Within a relatively few years of becoming exposed, they crumble away to unrecognizable gravel. Good fossil exposures are transient things.

Because of the temporary nature and physically limited size of fossil sites, many fossil-hounds develop a habit of being somewhat vague when describing where they've found a really nice specimen (at least until they have gotten to know you well). If you widely spread the news about some interesting site you found, you're more likely to find the site completely picked over the next time you visit. These days, I can imagine fossils being quickly stripped from a site for sale online. I don't have a problem with someone selling fossils, but I would definitely despair at finding an interesting site emptied between one visit and the next. Much of the value of an interesting fossil in the context. (The geologic era, what species were found with it, etc.) This information can easily be lost if a site is picked over with too much haste.

The former fossil site, now a movie theater.
I recently checked in on a site where I once found numerous wonderful fossils. The site was directly behind my high-school in San Antonio, Tx. Thanks to GoogleMaps, I now know it to be the parking lot for a movie theater. I have no problem with telling the wider world exactly where the site is located. There is no further damage over-exposure can do to it.

Previously, there had been a wide, flat hilltop covered with multi-pound specimens of Exogyra ponderosa (a reef-forming oyster), along with the numerous shells from several smaller relatives. The fossiliferous layer was the very top of the hill, so one could walk along and easily visualize how the ecosystem was organized back in the Cretaceous era when this hilltop was the floor of a shallow sea. Though all the animals had been extinct for 60 million years, the fossils were comprehensive enough to clearly be a well-populated oyster reef. The site was impressive. I expect ecological studies could have been done there. The nearby area of undeveloped land probably contains fossils, since much of Cretaceous limestone does, but the oyster reef did not extend into that area. The reef no longer exists and only the few fossils remaining from the site in the hands of collectors like myself (and the biology teacher who pointed me towards the site) are evidence for it having ever existed.

A ~6in long Exogyra ponderosa from the oyster reef.

I always meant to spend more time exploring the area, but the classes and drama of high-school always seemed to get in the way. When I graduated and moved on to college in Austin-Tx, my parents moved out of state. I no longer had any connection to the neighborhood. It wasn't until years later, when I too had moved out of state, that I got my first car and with it the freedom to go wandering around looking for fossils and the like.

Now I have other fossil sites to visit and keep quiet about. (For example, where I found another mollusk... the-biologist-is-in.blogspot.com/2014/05/a-gastropods-lesson.html).