Everything about The Ashfall Fossil Beds totally explained
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.
Bruneau-Jarbidge event
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 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.
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're 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
Species
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:
Further Information
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