Cretaceous Geologic Section of NE Mississippi and West Tennessee.

Mesozoic Era 245 to 65 Million Years

Cretaceous Period 146 to 65 Million Years

Upper Cretaceous marine sedimentary formations of the Mesozoic Era are present along the western edge of the Tennessee Valley and some units are fossiliferous. The Mesozoic Era is known as the age of the Dinosaurs and a few dinosaur teeth and bone fragments have been found in these marine sediments, normally identified as Hadrosaur. Cretaceous units in the Mississippi embayment area of the Tennessee Valley region has a great assortment of fossils for you to find, see Figure 9. Marine vertebrates are fairly common from place to place with shark and ray, fish - especially boney fish, sawfish, mosasaur, turtle, and crocodile like teeth and skeletal fragment have been found. Marine invertebrates are common especially mollusks but you can find some fossil crabs and lobsters, as well as plant fossils, and petrified wood. The oyster Exogyra (a Mollusk) is easy to recognize because of its large, thick, heavy shell and is the most common marine fossil found in the upper Cretaceous because of this. There are two Cretaceous fauna zones identified in the Mississippi Embayment, two species of Exogyra, E. costata from the Ripley Formation and E. ponderosa from the Demopolis Chalk. These fauna zones are used to correlate the variable local layers of the upper Cretaceous formations with other layers over a great distance.

The Tuscaloosa Group is the lowest unit of the upper Cretaceous present in the west Tennessee Valley region. The Tuscaloosa is composed of somewhat smooth spherical water worn cherts and quartzites forming pebbles and gravels that are mixed with a varied amount of sands and clays, a conglomerate unit. The pebbles and gravel are generally less than an inch in diameter but not uncommon larger and even areas with a good amount of smooth cobblestones mixed in has been observed. The only fossils collected from this unit has been petrified wood from northwest Alabama and were found in a unit contains more sand and clay with small pebbles.

The Tuscaloosa Group also has many locale layers of brown iron. Much later in its history these layers of iron were precipitated out of fresh water in the conglomerate units, at the top of the ancient water table of the area. The brown iron was heavily mined throughout the region before and during the Civil War and purified in smelters like in the pictures, Figures 10, and 11. Figure 11 is the only intact Furnace left I known of and several partials are scattered around the Silurian Glades area. Figure 10, the stone was reused elsewhere. Back in the day when these Furnaces were in operation the Silurian Glade area was known as the Coalings for the charcoal made. The Red Cedar Trees from the Silurian Glades were used to make charcoal for these furnaces thereby causing the erosion that helped to create the wonderful fossil sites.

The Demopolis and Coon Creek Formations are the most consistently fossiliferous Cretaceous units in the western area. Coon Creek is a famous Cretaceous fossil site and much literature has been published on the on this area along the western edge of the Tennessee Valley. I do enjoy collecting the Cretaceous fossil in northeast Mississippi and west Tennessee but due to my interests I have not spent much time collecting the Cretaceous. There’s a lot of fossil and variety in the Cretaceous of this area so it’s a wonderful place to spend your day collecting fossils.

Everyone has heard of the mass extinction of the dinosaurs at the end of the Cretaceous, K-T Boundary (Cretaceous-Tertiary Boundary). The theory that a single meteorite strike near the Yucatan Peninsula was largely responsible for this mass extinction event is a subject of debate among professionals. It is known that all the groups of life, terrestrial and marine, were undergoing a noticeable loss in species starting about 5-6 million years before the K-T Boundary. Many other geological events were going on around the Earth at the same time. A flood basalt event known as the Deccan Traps, that eventually cover an area about half the continent of Indian, was occurring at the same time near or at the end of the Cretaceous. Its environmental impact and effects on the K-T mass extinction is also a subject of debate. Remember all these fossil and geologic sites just provide us snap shot views of events on Earth at a particular place and time. We defiantly do not know everything that was going on all over the Earth at any certain time. These geologic and fossil sites give us clues that are interpreted to help give us answers to the history of Earth’s past.