04 Jun The Rocky History of Fearrington
Our title lends itself to two different meanings. It could mean that the development of Fearrington Village was a rocky or shaky undertaking. I doubt that neither Fitch Creations nor we would go along with that scenario. What I mean in this little essay is that rocks have played a fundamental role in the long period of geological change leading up to this special spot of earth.
Fearrington is rocky – not excessively but well enough endowed. Many boulders were on the surface or only partially exposed when development of Fearington Village got underway. We can still find them in our gardens or along the roads. Quantities have been uncovered and moved by road-building and housing developments. In some case, large ones were left intact in our lots, or others brought in as part of the landscaping.
Then, of course, Fearrington is underlain by what we call bedrock. I am not aware of an exposure here, but dig down far enough and there it is. That is what they do at quarries. There is one in Chatham County south of Pittsboro in route to Sanford on 15/501. A second, the American Stone Company, is west of Chapel Hill on 54. Much of the dark fractured rock from it has been brought into Fearrington to line drains (rip rap), and crushed stone for our road beds.
I thought some of you might be interested in knowing a little more about our rocks and how they got here in the first place, what they are like, and how they differ.
In writing this piece, I am drawing on my career as a soil scientist and amateur geologist. I was helped with some details by a specialist in the North Carolina Geological Survey, in particular as to why so many rocks appear on the surface. And importantly, my wife Ingrid and I have gained much relevant information in developing our rocky garden.
The topography of Fearrington generally reflects the topography of the underlying bedrock with gentle to fairly steep undulations. The surface crests or ridges of the latter tend to erode more rapidly and often enough to expose some of the parts of the bedrock. Weathering, change by chemical, physical and biological processes, fractures and changes surfaces of the rock resulting in the boulders we now encounter.
Not all of our rocks are the same. Basically they are classified as either felsic or mafic. Felsic means that the rocks are high in feldspars and quartz. Both these minerals are light in color, reflected in the relatively light color of felsic rocks. Probably at least 90% of our rocks are the light colored felsic. The rest are mafic. Mafic rocks are dark, as they are formed from basaltic magma(molten rock), and with heavier minerals containing iron and magnesium. To really appreciate the difference, look for some of each that have been fractured recently exposing the fresh un-weathered surface.
How do we account for these rather scarce, dark and heavy mafic rocks? Well, the predominantly felsic bedrock over time developed fissures or vertical cracks that allowed deeper dark mafic magma to flow upward. These filled fissures are known as dikes. So, we have one or more of these dikes in Fearrington that have given rise to our relatively scarce dark and heavy mafic rocks.
So, we have quite an interesting stony past and present. Learn more about our stones – where they are, how they look on closer examination, and how they are used. You don’t have to be a geologist to appreciate and enjoy them.
|By driving around the village you will encounter many large boulders. Some have been left in place outside and within gardens while others have been added to gardens to enhance the landscaping. Several good examples of naturally rocky gardens are found in the Creekwood area, for example, numbers 111 and 112 on Stone edge.
A notable example of their transported use is in Camden Park. They line the stream between the two ponds as well as serving as an embankment at the western end of the lower pond.
But virtually all these stones are the lighter-colored felsic. What about their scarcer, darker and heavier neighbors – the mafic? I suggest two places. First, check the entrance (photo above) off Village Way leading up by the silo and barn. The flower beds on either side of the entrance are walled by the dark ones. But really, they don’t look so dark. They have more of a brownish or rusty cast. That is because of weathering of the dark minerals, especially those containing iron. The result is a rust-like coating. This may be even more evident in my second example. During early roadbuilding in the village, many of these dark rocks were exposed in a couple of locations We brought in many to our gardening for landscaping. More recently, I decided to relocate quite a few to build a cairn to commemorate my Scottish heritage. It is located just off Beechmast in our garden before you get to Greystone (230).
In closing, I will note that the predominance of our felsic rock background is responsible for our light-colored, sandy and rather infertile soils. To compensate. many of us have resorted to use of chemical and organic fertilizers, or had top soil brought in. Where there is a will, there is a way.
So, learn more about our rocks. Walk in the park, or drive around the village. It can be rewarding!
|Guy B Baird
Photos: Jim Brooking