Ashfall Fossil Beds

From Wikipedia, the free encyclopedia

Coordinates: 42°26′26″N 98°08′53.1″W / 42.44056, -98.148083
Ashfall Fossil Beds State Historical Park
Protected Area
none The hills surrounding the fossil beds
The hills surrounding the fossil beds
Country United States
State Nebraska
Counties Antelope County
Coordinates 42°26′26″N 98°08′53.1″W / 42.44056, -98.148083
Area 360 acres (145.7 ha)
Founded 1991
Management Nebraska Game and Parks Commission
IUCN category III - Natural Monument
Location of Ashfall State Historical Park in Nebraska
Location of Ashfall State Historical Park in Nebraska
Website: Ashfall Fossil Beds State Historical Park

The Ashfall Fossil Beds of Antelope County in northeastern Nebraska are among the rare preservation sites called lagerstätte, which preserve ecological "snapshots" from a brief moment in time, due to extraordinary local conditions that have preserved a range of fossilized organisms undisturbed.

Contents

[edit] Bruneau-Jarbidge event

Main article: Bruneau-Jarbidge caldera

The Ashfall deposit preserves the fossilized remains of 10- to 12-million-year-old (Miocene) animals that perished in a dense volcanic ashfall; the animals had come to a waterhole seeking relief. The fall of ash drifted downwind from the Bruneau-Jarbidge supervolcano eruption (in present-day Idaho), nearly 1,000 miles (1600 km) west of the Ashfall site. A large number of very well-preserved fossil rhinos, small three-toed horses, camels, and birds have been excavated. Many animals were preserved with their bones articulated; one rhino still bears her unborn fetus, while others retain the contents of their last meal.

The fossil of a horse locked in volcanic ash.
The fossil of a horse locked in volcanic ash.

The bones of the animals show features that indicate that the animals died of lung failure induced by inhaling volcanic ash. The smaller animals with smaller lung capacity were the first to die, and the larger animals were the last. Bite-marks on some bones show that local predators (the carnivorous bone-crunching dog Aelurodon) scavenged some of the carcasses, but no predator remains have yet surfaced. There are also abundant clues to the region's ecology, indicating a savanna of grassland interspersed with trees that luxuriated in a warmer, milder climate than today's.

The rapidly-accumulating ash, windblown into deep drifts at low places like the waterhole site, remained moderately soft. The ash preserved the animals in three dimensions; not even the delicate bones of birds or the carapaces of turtles were crushed. Above the layer of ash, a stratum of more erosion-resistant sandstone has acted as "caprock" to preserve the strata beneath.

[edit] Preservation

The first hint of the site's richness was the skull of a juvenile rhinoceros noticed in 1971 eroding out of a gully at the edge of a cornfield. The Ashfall site became Ashfall Fossil Beds State Historical Park in 1991. Newly uncovered fossils are being left exactly as they are found: specially constructed walkways afford visitors an unobstructed close-up view of paleontologists at work during the summer field season. The site was declared a National Natural Landmark on May 9, 2006[1]

[edit] Species

The most common animal is Teleoceras.
The most common animal is Teleoceras.

The remains of Teleoceras are so numerous and concentrated that the main section of Ashfall is dubbed the "Rhino Barn". Other fossils at the "Rhino Barn" include the remains of horses and camels. Taxa discovered in the Ashfall deposits include:

[edit] See also

[edit] References

  1. ^ Acting Interior Secretary Scarlett Designates Ashfall Fossil Beds A National Natural Landmark. United States Department of the Interior (2006-05-09). Retrieved on 2006-06-11.

[edit] External links