White Rock takes up over 1,000 acres of our community and has been around for over 100 years. The reservoir and the land around it has become a haven for runners, kayakers, bikers and every other kind of nature-centric person you can think of. But besides what we use it for, what do we really know about it geologically?
What makes White Rock’s rock white?
Try to say that five times fast. We know we couldn’t. The answer is quite simple, at least it is to Amy Martin— a veteran journalist and the author of Wild DFW, a book that breaks down the nature in and around the metroplex. She says it’s because the rocks are limestone.
“We’re the land of limestone,” Martin cracks a smile as she says it.
Our limestone is called Austin Chalk which is made up of microscopic fossils from the Cretaceous Era, a period that ended 66 million years ago, according to the Natural History Museum. Martin says that during this time period “we used to be in the middle of an ancient inland sea.” There would be times that it could be as “deep as a skyscraper “ and a considerable amount of microscopic creatures made the sea its home. When they died, their remains would settle at the bottom and with time and pressure, they became the white rock we see today.
Are there other marine creature fossils in the area today?
Yes. Although it’s rare to find them in our area. More shallow portions of the sea, towards Fort Worth, would catch most of the creatures near the shoreline. Occasionally, if you’re lucky, you could find an ammonite fossil. The remains used to float and have coiled external shells that resembled that of a large snail. Martin alludes to the areas of the park that have these particular fossils as being a sort of invite-only viewing experience. If you know where to find them, then you know. If you don’t, you don’t. Don’t worry, we didn’t get an invite to the cool kids club either.
What other geological features are native to the area?
Our dirt. Hang with us here. Dirt can be special too, especially since ours comes from Austin Chalk.
“Whatever your bedrock is, creates the soil that you have,” Martin says. Since the Austin Chalk is soft, it can be assumed that it was formed in shallow waters with less pressure weighing it down. Over time, Martin says that limestone would leach out and the only thing remaining is the organic matter, and pyrite.
“Over millions of years, that white limestone leaches out and becomes black gumbo dirt, the stuff we garden with,” Martin says.
This dirt, filled with marine plants and microscopic marine organisms from millions of years ago, is extremely fertile. “It’s full of good stuff, and it’s got a lot of minerals in it.”
