Since childhood fossils have fascinated me. Maybe it was my grandparents’ travels to the Petrified Forest during their Southwest vacations. Maybe it was reading about archaeology and discoveries of dinosaurs. In any case, I had the impression that fossils were rare items found in some dig far away. Subsequently, I have had opportunities to see those petrified trees exposed in the desert and dinosaur skeletons displayed in museums. Finding a fossil still seems to be something a better trained eye would do. However, recently, while clearing rocks from a washed-out area, I came across a rock with a pattern.
You may recall that we had flash floods back in May. In the course of a few hours, seasonal stream which usually trickle with Spring snow melt, rose several feet after heavy thunder showers. Some sections of these streams became blocked by fallen trees and branches. Other sections were scoured clean of rocks of all sizes. Several sections of our land association’s roads were crossed by water spilling over the banks.
Before Fall starts filling the ditches with leaves and Winter freezes the road bed, I have been using my tractor to clean up rougher sections. While tossing rocks out of the flow of the stream, I noted one rock that had a series of pencil-diameter sized circles on both sides.
Most of the rocks in this stream bed were shale, sandstone, or an occasional block of limestone. Most have flat, squared sized, with variations of brown to tan coloring. This rock was average in size and color, but looked pocked from all the small circles on its surface.
Initially, I thought that it might be shells. But, unlike most shells, which are more oval-shaped, these were true circles. Also, each circle had a second, smaller central circle, then a starburst pattern of lines radiating out from the smaller to the larger circle.
I set the rock aside, until I finished the project of tossing the other rocks on the edge of the stream. I took it home for closer inspection. In addition to my visual inspection, I wanted to compare it against other information that I had about fossils.
Back to that trip to the Petrified Forest, I had found a book on petrified plants. I had recalled when reading this a few years back, seeing a similar pattern of close circles. Without much difficulty, I found the chapter on petrified ferns. What I was most likely looking at was a 1.5 inch thick cross-section of the base of the fern plant.
The circles were the individual stems of each branch. The cluster of circles was the close origin of the stems from the root base. Ferns, such as this, may have grown in a marshy area. A flash flood some time ago, may have covered the plant with silt. The silt became buried, then compressed in rock. The carbon based plant tissues became replaced by minerals, leaving the fossil image that I found.
Well, my fossil may not be as impressive as those tree-sized red quarts pillars in the desert. But, I know which seasonal stream it came from…. and, it can sit on my table.