The Gray Fossil Site is an Early Pliocene assemblage of fossils dating between 4.5 and 4.9 million years old, located near the community of Gray in Washington County, Tennessee. The site was discovered during road construction on Tennessee State Route 75 by the Tennessee Department of Transportation in May 2000, [1] [2] after which local officials decided to preserve the site for research and education. [3] [4] The site became part of East Tennessee State University, and the Gray Fossil Site & Museum was opened on the site in 2007.
The ancient habitat of the Gray Fossil Site was a pond formed within a sinkhole surrounded by a warm, wet forest. The fossils found at the site represent the ancient plants and animals that lived and died in and around the sinkhole pond.
As the first site of its age known from the Appalachian region, the Gray Fossil Site is a unique window into the past. Research at the site has yielded many surprising discoveries, including new species of red panda, rhinoceros, pond turtle, hickory tree, and more. The site also hosts the world's largest known assemblage of fossil tapirs.
The Gray Fossil Site is a deposit of laminated clay and silt sediments laid down in an ancient lake that formed within a sinkhole. The deposit is oval in shape, covering an area of roughly 220 meters by 180 meters and ranging in depth from about 7 meters to 39 meters deep. The fossils within this deposit are abundant and often exceptionally well-preserved. [5]
The site is situated within the Knox Group formation, a series of Cambrian-Ordovician limestones. Groundwater flowing through joints in these rocks creates caves and sinkholes, forming a region of karst topography. The sinkhole that contains the fossil-rich deposits of the Gray Fossil Site is the result of a series of overlapping collapse events that ultimately formed one large basin. Sizable boulders deposited within the lake sediments indicate that the edge of the sinkhole once featured high walls or overhangs where chunks of rock could occasionally break off. [5]
Based on the assemblage of mammal fossils uncovered at the site, the main deposit is estimated to date between 4.5 and 4.9 million years old, during the Early Pliocene Epoch near the transition of the Hemphilian and Blancan Land Mammal Ages. [6] There is some evidence from drill cores for more ancient deposits deeper within the site, resulting from earlier stages of sinkhole collapse. [5]
In late May 2000, this fossil-rich deposit was discovered during a Tennessee Department of Transportation road construction project on the outskirts of Gray, TN. As it became clear that the fossils were unusual for this part of the country, members of the local community began an effort to preserve the site. In September 2000, Tennessee Governor Don Sundquist announced that the construction project would be moved so the fossil site could be saved and dedicated to research and education. [7]
The Gray Fossil Site then became a project of East Tennessee State University, which began hiring paleontologists and geologists to oversee the site and ultimately to create a new Department of Geosciences. The university founded the Don Sundquist Center of Excellence in Paleontology and began construction of an on-site museum to house research facilities and educational exhibits. The museum first opened in August 2007, originally known as the East Tennessee State University and General Shale Brick Natural History Museum and Visitor Center, but now known more simply as the Gray Fossil Site & Museum. [7]
The Gray Fossil Site was once a lake or pond surrounded by forest. The ancient lake was home to a diverse community of aquatic animals, including fish, pond turtles, aquatic salamanders, beavers, and alligators. [6] Plant fossils found at the site, particularly pollen, indicate that the dominant vegetation of the forest was oak, hickory, and pine trees, along with various herbaceous species. [8] Estimates for the density of this forest have varied; earlier research suggested a moderately dense forest, while later study indicated that the site might have been more of an open woodland where disruptive factors such as large herbivores, frequent fire, and drought limited the development of a closed canopy. [9]
A 2020 study used fossil mammal teeth as a proxy to estimate the ancient climate conditions of the Gray Fossil Site, estimating a mean annual temperature of 16.8 °C, or 62.2 °F (similar to modern-day Atlanta, GA), and an annual precipitation of 1,343mm, or 52.9in (similar to modern-day Tampa, FL), with the minimum temperature of the coldest month reaching 2.6 °C, or 36.7 °F. [10] These results line up with earlier hypotheses that the site had a warmer and wetter climate than modern East Tennessee based on the presence of warm-climate animals and plants like alligators, tupelo, and Corylopsis . [9]
Many of the fossil fauna and flora of the Gray Fossil Site are closely related to modern-day species in Europe and Asia, including red pandas, European badgers, Chinese moonseed, and Corylopsis. This indicates that during the Early Pliocene, eastern North America maintained a biogeographic link with Eurasia. [11] [12]
The Gray Fossil Site is a Lagerstätte that boasts a rich assemblage of well-preserved fossils. It is the only fossil site in the Appalachian region dating near the boundary between the Miocene and Pliocene Epochs, and therefore offers a unique window into this region at this time. [13]
So far, all of the fish fossils identified at the Gray Fossil Site belong to the family Centrarchidae. [14]
A preliminary study in 2011 identified several families of birds at the Gray Fossil Site, the most common of which were ducks. [19]
Perissodactyls (odd-toed hoofed mammals)
Artiodactyls (even-toed hoofed mammals)
Proboscidea (elephants)
Aquatic invertebrates of the Gray Fossil Site include ostracods, snails, and small clams. [31] Insects are also known from fossilized exoskeletal remains and trace fossils, including at least four different families of beetles. [32]
Plant fossils at the Gray Fossil Site include pollen, leaves, wood, fruits, seeds, and other structures which represent a diverse flora of angiosperms, conifers, ferns, lycophytes, and bryophytes. [11] [33] The forest flora was dominated by a variety of trees and shrubs, of which the most common were hickory, oak, and pine. [11] [9]
Several previously unknown extinct plant species have been identified at the Gray Fossil Site: [11] [9]
Algal microfossils have been identified as numerous freshwater species, including one previously unknown extinct species, Stigmozygodites grayensis, named after the Gray Fossil Site in 2013. [33]
Several types of fungi have been identified from microfossil remains of fungal tissue and fruiting bodies. [34]
The Pliocene is the epoch in the geologic time scale that extends from 5.33 to 2.58 million years ago (Ma). It is the second and most recent epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian Stage, which lasted from 2.59 to 1.81 Ma, and is now included in the Pleistocene.
A pika is a small, mountain-dwelling mammal native to Asia and North America. With short limbs, a very round body, an even coat of fur, and no external tail, they resemble their close relative, the rabbit, but with short, rounded ears. The large-eared pika of the Himalayas and nearby mountains lives at elevations of more than 6,000 m (20,000 ft).
Teleoceras is an extinct genus of rhinocerotid. It lived in North America during the Miocene and Pliocene epochs during the Hemingfordian to the end of Hemphillian from around 17.5 to 4.9 million years ago. It grew up to lengths of 13 feet long.
The Pipe Creek Sinkhole near Swayzee in Grant County, Indiana, is one of the most important paleontological sites in the interior of the eastern half of North America. It is preserved because it was buried by glacial till. Uncovered in 1996 by workers at the Pipe Creek Junior limestone quarry, the sinkhole has yielded a diverse array of fossils from the Pliocene epoch, dating back five million years. Discoveries have been made there of the remains of camelids, bears, beavers, frogs, snakes, turtles, and several previously unknown species of rodents. Two fish taxa, bullhead (Ameiurus) and sunfish (Centrarchidae), have also been found there.
Trachemys is a genus of turtles belonging to the family Emydidae. Members of this genus are native to the Americas, ranging from the Midwestern United States south to northern Argentina, but one subspecies, the red-eared slider, has been introduced worldwide. Species under this genus are commonly referred to as sliders.
Deirochelys is a genus of freshwater turtle in the family Emydidae, the pond and marsh turtles. It contains one extant species, the chicken turtle, which is native to the southeastern United States. A second extinct member, Deirochelys carri, is known from a fossil found in Alachua County, Florida. The genus was first described by Louis Agassiz in 1857, and its name is derived from the Ancient Greek words for "neck" (deirḗ) and "tortoise" (khélūs), referring to the particularly long necks of these turtles.
The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma. It follows the Tortonian and is followed by the Zanclean, the first age of the Pliocene.
Chrysemys is a genus of turtles in the family Emydidae. They are found throughout most of North America.
Macrochelys is a genus of very large freshwater turtles in the family Chelydridae, native to the Southeastern and Midwestern United States. Only a single extant species was recognized until 2014, when a study divided it into two or possibly three species. These turtles are easily recognized by three distinct dorsal ridges with raised spikes.
Clemmys is a genus of turtles currently containing a single extant species, the spotted turtle (Clemmys guttata).
Guloninae is a subfamily of the mammal family Mustelidae distributed across Eurasia and the Americas. It includes martens and the fisher, tayra and wolverine. These genera were formerly included within a paraphyletic definition of the mustelid subfamily Mustelinae.
Pseudhipparion is an extinct genus of three-toed horse endemic to North America during the Miocene. They were herding animals whose diet consisted of C3 plants. Fossils found in Georgia and Florida indicate that it was a lightweight horse, weighing up to 90 pounds. In 2005, fossils were unearthed in Oklahoma. Seven species of Pseudhipparion are known from the fossil record which were very small, following the trend of Bergmann's rule.
Cormohipparion is an extinct genus of horse belonging to the tribe Hipparionini that lived in North America during the late Miocene to Pliocene. They grew up to 3 feet long.
The Peace River Formation is a Late Oligocene to Early Miocene geologic formation in the west-central Florida peninsula.
The Western North Carolina Nature Center is a 42-acre (17 ha) zoological park in Western North Carolina operated by the City of Asheville's Parks and Recreation department. Until 1973, it was known as the Asheville City Zoo and was then renamed the Children's Zoo and Nature Center. It received its current name in 1974 when formed as a non-profit charity to develop the zoo which ultimately opened in 1976. The Center has been accredited by the Association of Zoos and Aquariums since 1999 and its collection features animals native to the southern Appalachian Mountains. In 2013 the center welcomed over 107,000 guests with over 13,000 coming from school children on field trips to the facility.
Paleontology in Tennessee refers to paleontological research occurring within or conducted by people from the U.S. state of Tennessee. During the early part of the Paleozoic era, Tennessee was covered by a warm, shallow sea. This sea was home to brachiopods, bryozoans, cephalopods, corals, and trilobites. Tennessee is one of the best sources of Early Devonian fossils in North America. During the mid-to-late Carboniferous, the state became a swampy environment, home to a rich variety of plants including ferns and scale trees. A gap in the local rock record spans from the Permian through the Jurassic. During the Cretaceous, the western part of the state was submerged by seawater. The local waters were home to more fossil gastropods than are known from anywhere else in the world. Mosasaurs and sea turtles also inhabited these waters. On land the state was home to dinosaurs. Western Tennessee was still under the sea during the early part of the Cenozoic. Terrestrial portions of the state were swampy. Climate cooled until the Ice Age, when the state was home to Camelops, horses, mammoths, mastodons, and giant ground sloths. The local Yuchi people told myths of giant lizard monsters that may have been inspired by fossils either local or encountered elsewhere. In 1920, after local fossils became a subject of formal scientific study, a significant discovery of a variety of Pleistocene creatures was made near Nashville. The Cretaceous bivalve Pterotrigonia thoracica is the Tennessee state fossil.
Ochotona spanglei is an extinct species of pika, known from Late Miocene - Early Pliocene fossil from Oregon (USA). Fossils were also found in Nebraska referred to as Ochotona cf. spanglei.
The Bone Valley Formation is a geologic formation in Florida. It is sometimes classified as the upper member of the Peace River Formation of the Hawthorn Group. It contains economically important phosphorite deposits that are mined in west-central Florida, as well as rich assemblages of vertebrate fossils.
The Capistrano Formation is a geologic formation in coastal southern Orange County, California. It preserves fossils dating back to the late Miocene to early Pliocene, with the Oso Member representing a near-shore environment. Fifty-nine species and varieties of foraminifera are recognized from the Capistrano Formation alongside a diverse array of marine mammals including up to five species of walrus.
The Pisco Formation is a geologic formation located in Peru, on the southern coastal desert of Ica and Arequipa. The approximately 640 metres (2,100 ft) thick formation was deposited in the Pisco Basin, spanning an age from the Late Miocene up to the Early Pliocene, roughly from 9.6 to 4.5 Ma. The tuffaceous sandstones, diatomaceous siltstones, conglomerates and dolomites were deposited in a lagoonal to near-shore environment, in bays similar to other Pacific South American formations as the Bahía Inglesa and Coquimbo Formations of Chile.