10/01/2026
Simpson County Gravel — A Geological Mystery, Part I
Images of gravel used with this article are from a 2008 circular published by the Mississippi Department of Environmental Quality, Office of Pollution Control and Office of Geology.
First of all, I am not a geologist. I am, however, a very interested researcher who has spent considerable time studying the history and landscape of Simpson County. To understand part of the county’s geologic history, one only has to look at the extensive gravel deposits found across it. Gravel has been so common here for generations that it is easy to overlook, but its distribution, composition, thickness, and elevation raise some important questions.
As a boy growing up in Simpson County, I spent hours crouched over our gravel driveway searching for little treasures. Some stones were brightly colored, while others contained circles, shells, spirals, and other fossil patterns. I also remember my grandparents arranging for truckloads of gravel to be dumped and spread along our long driveway. At one time, a large percentage of Simpson County’s rural roads were gravel roads, and much of that material came from local gravel pits.
The earliest commercial gravel operation I have identified in Simpson County was associated with the Gulf & Ship Island Railroad. Its gravel pit was located in the general area where Simpson Academy and Howard Industries are today. During the early 1900s, gravel was excavated there with steam-powered equipment and hauled away by railroad. Thousands of tons were used for railroad beds and road construction. The operation demonstrates that the county’s gravel was not merely a thin scattering of stones at the surface. In places, the deposits were large and thick enough to support commercial mining.
Many additional pits were opened across Simpson County during the twentieth century. Some were commercial operations, while others were smaller borrow pits supplying local roads and construction. Many are now overgrown, hidden beneath woods, converted into ponds, or altered by later development. Using U.S. Geological Survey topographic maps, historical aerial photographs, modern LiDAR, and ground observations, I have so far identified 74 individual gravel pits in 44 township-range-section combinations within Simpson County. That is almost certainly not a complete inventory, since smaller pits may never have been mapped and others may remain hidden.
The known pits extend across the Magee, Mendenhall, D’Lo, Weathersby, Saratoga areas and beyond. Their approximate elevations range from 300 feet to 535 feet above sea level. This is one of the most interesting facts about the deposits. The highest known gravel occurrences lie far above the beds of present-day streams. The Strong River at D’Lo, for example, occupies a valley hundreds of feet below the highest gravel-bearing uplands.
The gravel itself is distinctive. It is predominantly composed of honey-colored chert derived from marine Paleozoic bedrock of the Tennessee and Ohio River valleys. The deposits also contain quartz, quartzite, agate, carnelian, jasper, and petrified wood. Agate, carnelian, chalcedony, and jasper are among the attractive lapidary or gemstone materials that can be found within these gravels.
Many of the chert stones contain fossils or remains and traces of ancient life with the presence of crinoids, corals, brachiopods, and bryozoans. These fossils are much older than the gravel deposits themselves. They formed in ancient marine rocks long before pieces of those rocks were eroded, transported, and eventually deposited in south-central Mississippi.
That distinction is important. The age of a stone is not necessarily the age of the deposit in which it is now found. A chert pebble containing a Paleozoic fossil may be hundreds of millions of years old, but that does not tell us when the pebble arrived in Simpson County. A stone can be eroded from its original bedrock, transported, deposited, exposed again by later erosion, and transported a second time.
What we can say with confidence is that moving water transported the gravel. Rounded and subrounded stones record repeated movement and abrasion. What remains uncertain is the exact hydraulic system responsible for bringing this material into Simpson County and placing it at the elevations where it is now found. Large rivers, braided channels, repeated high-energy floods, later reworking of older deposits, or some combination of these processes are all possibilities that must be tested against the physical evidence.
The position of the gravel pits may provide another clue. Many of the identified pits are not located on the absolute tops of the highest ridges. Instead, numerous pits occur along slopes or around the margins of upland remnants. Erosion cutting into a hillside can expose that buried gravel, making it accessible for mining.
The potential quantity of material involved is enormous, although it cannot yet be measured precisely. If the approximately 412 square miles mapped as Magee Airport Terrace contained an average of only one foot of net gravel, using an illustrative bulk density of about 1.4 tons per cubic yard, that would represent roughly 600 million tons. An average of three feet would approach 1.8 billion tons, while five feet would approach 3 billion tons.
Those numbers are not estimates of proven reserves. They are calculations intended only to demonstrate scale. The actual thickness and continuity of the gravel vary, the proportion of gravel to sand, silt, and clay is not known countywide, and enormous quantities have already been removed by both natural erosion and human mining.
The 74 known gravel pits are therefore more than abandoned mining sites. They are points where portions of a much larger geological deposit have been exposed. They show that gravel occurs across a broad part of Simpson County, at elevations ranging from about 300 to 535 feet, and that at least part of the material originated hundreds of miles to the north.
What remains unresolved is when the gravel reached Simpson County, whether it was transported once or reworked several times, what hydraulic conditions moved it, and how much of the original deposit has since disappeared.
Those unanswered questions are what make Simpson County’s gravel a geological mystery.
To Be Continued- Part II — The Stones That Traveled Hundreds of Miles will look more closely at the chert, quartz, quartzite, agate, carnelian, jasper, petrified wood, fossils, and other stones found in the deposits, where they originated, and what they may tell us about the history of the gravel.
