INTERPRETATION OF ENIGMATIC BURROWS WITHIN THE UPPER CRETACEOUS OWL CREEK FORMATION, TIPPAH COUNTY MISSISSIPPI

Fossiliferous, irregular, shaped pods (“Honey Holes”) containing diverse assemblages are found scattered within the upper Maastrichtian Owl Creek Formation (Tippah County, MS). The Owl Creek Fm. is a micaceous, quartz rich, muddy, very fine sand with little variation in lithology through the 10 meter sampled section. Three pods were collected as bulk samples from differing stratigraphic positions (0.5m, 5.0m and 7.7m level) to test changes (size, shape, biodiversity and species richness) in the burrows through time. The fossil content within the densely compacted pod shaped burrows is mostly clast supported. Taphonomically, the burrows consist of a shell hash including a mix of whole and broken material from a diverse predominantly macroinvertebrate assemblage including bivalves, gastropods, ammonites, echinoids, and vertebrae. Broken hash, mostly less than 0.5cm in diameter, composed close to 90% of the material in the burrows. Biodiversity ranged from 0.90 (Simpson Diversity Index (1-D)) at the base of the sequence to 0.82 towards the top representing a fairly diverse assemblage. Species richness varied from 28 at the base to 17 at the top. Ammonites and pectens occurred in the highest concentrations within the pods composing 25% and 17% of the fossil assemblages, respectively. The similarity in paleontological and sedimentological features along with consistency in shape and size suggests that the inhabitants of these burrows had similar life habits. Small variations in species richness and biodiversity between different “honey holes” could be attributed to slight changes in environments or preservation biases. When compared to modern burrows, these fossil concentrations most closely resemble burrows of modern lobsters.