Selma Chalk Layer Exposed Downtown

Last August I blogged about a good development in downtown Starkville. Rick Underwood has made a lot of progress on his furniture boutique since then and I plan update that post in the near future. In terms of addressing the street and creating density, Rick is doing everything right. His rehabilitation of the old structure emphasizes how out-of-place the Bordon plant across the street looks. The Bordon plant is landscaped like a suburban office park. With no pedestrian connection to Bell's Building Supply next door, it seems to not know where it is. It doesn't realize that it is downtown. But that is a subject for another post.

An updated version of the furniture store, as of February.

This post is about the construction site diagonally across from Ricks furniture boutique. The electrical supply shop, auto body shop, and parking lot have been removed and the grading nearly completed for the installation of a large building on that lot. Here is an aerial image from 2007 with the lot delineated in orange. This image does not show the work done on the Borden Plant, which is the long building along the railroad tracks to the left of the orange rectangle.

The process of grading has revealed a very clear profile of the Selma chalk that underlies the red clay of Starkville. Starkville is on the western edge of the Black Belt Prairie physiographic region, which is crescent-shaped and extends across northeast Mississippi and south-central Alabama. At the time of European settlement, much of this area was open prairie with scattered woodlands and forested creek bottoms. A good, quick description of the Black Belt Prairie Region can be found here.

The Selma chalk is a Cretaceous marine formation and the prairie patches tend to occur where it is close to the surface. Generally this is on slopes. In the Black Belt, many ridges support groves of post oak or blackjack oak. Bottoms are more silty. But the assemblage of grasses and forbes extends into both ridges and bottoms, with subtle changes in palette. More on this later when I report on the Southeastern Prairie Symposium I attended last week.

Work at the southeast corner of Lampkin and South Montgomery Streets has revealed an area where the Selma chalk is very near the surface. Late in the day, when the sun is low in the west, this exposed face is particularly interesting to look at. I created several panoramic images using shots from my Nikon coolpix point-and-click camera. I wanted to preserve an image of this structure before it becomes hidden forever.

 Above is a view looking south from the northeast corner of the site. This is a gentle, north-facing slope with the chalk a foot or two below the surface. In a natural setting, this slope might have supported a blackland prairie with an oak-dominated woodland or forest on the red clay at the top. Prairies have been said to occur on cuestas. My understanding is that a cuesta is where the dip of the strata intersects with the angle of the slope. I find it plausible that we are looking at a cuesta here.

Above is one of my favorite graphic depictions of how cuestas are situated in the Gulf Coastal Plain. Note that the Selma formation is associated with the Black Belt. In reality the angle of the dip is not nearly as severe. From Nevin Fenneman's Physiography of Eastern United States 1938.

Five photos I stitched together. The brown clay building foundation is flat in reality but distorted in this image.

 Marl layer up close. I use the terms "marl" and "chalk" interchangeably. That is probably incorrect. 100 million years ago this was ocean floor.

Another five photos stitched together. At the southern end of the site the marl dips below the building foundation level. The acid cap effect takes over. Not sure what the black strata is, perhaps a layer of topsoil that was buried when the auto-body shop was constructed.

While trying to find some information about chalk outcrops in this area I came across a blog about student geologists from the College of Wooster exploring Mississippi that I found interesting.

I honestly know very little about geology and soils. There is always more to learn. It was interesting having this going on just a block from my house while preparing for the Southeastern Prairie Symposium, which I will write about soon.