STRATIGRAPHY & DEPOSITIONAL ENVIRONMENT
The mine itself is an open-pit phosphate mine on the south shore of the Pamlico River which exposes: Pungo River Marl (Lower Miocene), Yorktown ( Early Pliocene), Chowan River (Late Pliocene) and James City (Pleistocene) Formations. Fossils are collected at the mine or from tailings used by local highway departments as road fill. The latter usually have a Pungo River origin and are highly fossiliferous.
The Pungo River unconformably overlies the Castle Hayne Limestone (Eocene) and is comprised of 45 feet of interbedded phosphatic sands, silts & clays, diatomaceous clays and phosphatic limestone. The lower phosphatic levels were thought to have been deposited in an outer shelf environment and the upper calcareous beds, inner shelf. The 65 feet of Yorktown exposure is primarily clayey sands, often with abundant mollusk fossils. It unconformably overlies the Pungo River with marked channels. The lower units contain reworked Pungo River phosphate pebbles.
During the Miocene, this site was part of the Albemarle Embayment, itself situated in an area between what is today central North Carolina and the Virginia border. Early studies of fossil benthonic foraminifera suggested a cool-temperate Early and warmer Upper Miocene marine environment, which contradicted the limestone deposits in the Pungo River Formation. Subsequent research of marine currents concluded that a strong thermocline existed within this oceanic embayment during the Lower Miocene, leading to these contradictory results. The current opinion is that the Pungo River was created in a sub-tropical marine environment. Lower units were likely deposited in deeper water (to 100-200 meters). The last Pungo River deposits appear to reflect waters of under 70 meters.
The Yorktown unconformably overlies the Pungo River. It is thought that the closing the Panamanian isthmus created a faster oceanic current which ultimately drove the thermocline higher within the embayment leading to a cooler marine environment - warm-temperate. The lowest units are thought to have been deposited in waters from 80 to 100 meters, growing shallower over time. The upper most deposits were lain in waters of 15 meters or less. For the purposes of this study, specimens were derived from middle to upper Pungo River and basal Yorktown units.
THE FAUNA
It would be nice to provide an extensive list of what this site yields, but that's well beyond the scope of this website which attempts to limit itself to the sharks and rays. A quick overview of the fuana would include:
SHARKS. Aurora can provide the collector with shark teeth (vertebrae, cartilage and/or dermal denticles) from some fifty species. Most of the species included in the Non-Carcharhiniforme and Carcharhiniforme web pages, are also listed in the Purdy et al (2001), the Smithsonian publication. An attempt has been made to indicate how widely accepted certain identifications are. There is no general concensus on the make-up of the fauna, but it can be safely said that it is quite diverse. The shark list, as presented, places a great emphasis on the opinions of Bob Purdy, Bill Heim and the author. Because there is not 100% agreement, the lisiting includes comments if there is more than one opinion.
SKATES and RAYS. Batoid teeth are a very common constituent of the tailings but, because of their small size, most are unfamiliar to many collectors. The Ray Species List will provide a guide to many of the species that donated teeth, dermal denticles and vertebrae to the fossil record.
BONY FISH. Like other groups of Lee Creek fossils, the jaws, skull elements, otoliths and vertebrae of many fish accompany the collector home. A faunal overview Teleost species has been provided.
OTHER VERTEBRATES. Reptile material is found in the mine and turtle is most common. Bird bones are often found with Auk (Alca sp) being most common. The author has collected gannet/booby, cormorant, shearwater, loon and what might prove to be a tropic-like bird. After fish, mammals are the most ground-cluttering vertebrate fossils and porpoise & whales are the primary PaleoLitterbugs. Vertebrae and other bones are all over the place. The mine produces material from whales (sperm, the extinct Squalodon, etc.), porpoise, walrus and seals. Terrestrial mammal material, (primarily teeth) is also found on occassion.
INVERTEBRATES. In some areas of the mine, the only thing to walk on is fossils; invertebrates are everywhere -- corals, clams and snails. With the slightest attention, bryozoan, echinoderm, and crab material becomes evident. Finding nice stuff is easy, identifying it is much harder. Most Aurora collectors I've met see fossil invertebrates as index fossils for vertebrate material, not collectable unless particularly beautiful. With this said, Aurora can be a gold mine for invertebrates and there are collectors that visit for that purpose.
REFERENCES
Gibson, T. 1967. Stratigraphy and Paleoenvironment of the Phosphatic Miocene Strata of North Carolina. Geological Society of America Bulletin. Volume 78, pp 631-650.
Purdy, R., Schneider, V., Appelgate, S., McLellan, J., Meyer, R. & Slaughter, R., 2001. The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In: Geology and Paleontology of the Lee Creek Mine, North Carolina, III. C. E. Ray & D. J. Bohaska eds. Smithsonian Contributions to Paleobiology, No 90. Smithsonian Institution Press, Washington D.C. pp. 71-202.
Ray, C. (editor) 1987, Geology and Paleontology of the Lee Creek Mine, North Carolina, II. Smithsonian Contributions to Paleobiology, 61. Smithsonian Institution Press, Washington D.C. 283 pp.