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〕 | area_unit = acre | area_imperial = 360 | area_round = 0 | area1_imperial = | area1_type = | length_imperial = | length_orientation = | width_imperial = | width_orientation = | highest = | highest location = | highest_lat_d = | highest_lat_m = | highest_lat_s = | highest_lat_NS = | highest_long_d = | highest_long_m = | highest_long_s = | highest_long_EW = | highest_elevation_imperial = | lowest = | lowest_location = | lowest_lat_d = | lowest_lat_m = | lowest_lat_s = | lowest_lat_NS = | lowest_long_d = | lowest_long_m = | lowest_long_s = | lowest_long_EW = | lowest_elevation_imperial = | biome = | biome_share = | biome1 = | biome1_share = | geology = | geology1 = | plant = | plant1 = | animal = | animal1 = | established_type = | established = 1991 | established1_type = | established1 = | management_body = Nebraska Game and Parks Commission | management_location = | management_lat_d = | management_lat_m = | management_lat_s = | management_lat_NS = | management_long_d = | management_long_m = | management_long_s = | management_long_EW = | management_elevation = | visitation = | visitation_year = | free_type = | free = | free1_type = | free1 = | map = Nebraska Locator Map.PNG | map_caption = Location of Ashfall State Historical Park in Nebraska | map_locator = Nebraska | map_first = | website = (Ashfall Fossil Beds State Historical Park ) | footnotes = }} The Ashfall Fossil Beds of Antelope County in northeastern Nebraska are rare fossil site types called lagerstätten that, due to extraordinary local conditions, capture a moment in time ecological "snapshot" in a range of well-preserved fossilized organisms. Ash from a Yellowstone hotspot eruption 10-12 million years ago created these fossilized bone beds. The Ashfall Fossil Beds are especially famous for fossils of mammals from the middle Miocene geologic epoch. The Ashfall Fossil Beds are stratigraphically part of the Serravallian-age〔Often called Clarendonian in North American contexts.〕 Ogallala Group. The site is now protected as Ashfall Fossil Beds State Historical Park, which includes a visitor center with interpretive displays and working fossil preparation laboratory, and a building over an ongoing excavation site featuring fossil ''Teleoceras'' (native hippo-like ancestral rhinoceros) and ancestral horses. == Bruneau-Jarbidge event == (詳細はMiocene, approximately 12 million years ago; 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 west of the Ashfall site. A large number of very well preserved fossil ''Teleoceras'' (extinct hippo-like relatives of rhinos), small three-toed and one-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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ashfall Fossil Beds」の詳細全文を読む スポンサード リンク
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