The Hagerman Horse Quarry
Encyclopedia
The Hagerman Horse Quarry is a paleontological site containing the largest concentration of Hagerman Horse
fossils yet found. The quarry is within Hagerman Fossil Beds National Monument
, located west of Hagerman, Idaho
, USA, at the geographic division of the Snake River
Plain. The Hagerman Horse Quarry is an integral part of the monument and is located on the northern flank of Fossil Gulch in the northern portion of the monument.
The Hagerman Horse Quarry resides near the top of the hillside of Smithsonian Hill. The hill was named from the early Smithsonian excavations of the Hagerman horse
(Equus simplicidens). The Hagerman Horse is the first fossil representation of the genus
Equus
in North America.
Historically, the Hagerman Horse Quarry was divided into three informal subquarries, the red, the green and white quarry sandstone
s. Fossils are found throughout the monument; however the Horse Quarry continues to be the focus of paleontological research.
The Hagerman Fossil Beds National Monument visitor center is administered by the National Park Service
. There is a skeleton reconstruction of a Hagerman Horse at the visitor center in Hagerman, Idaho. The Hagerman Fossil Beds National Monument reopened the Hagerman Horse Quarry during the summer of 1997. The Hagerman Horse Quarry is closed to visitors.
, who in turn brought it to the attention of Dr. James W. Gidley of the Smithsonian Institution
. The Smithsonian Institution field crew excavated from all three quarry beds during the years 1929-1931 and 1934 (Richmond and others, 2002).
The University of Utah
, under the direction of Mr. Golden York, acquired fossils from the quarry in 1953. The Natural History Museum of Los Angeles County
managed their excavation during the summer of 1966. The Idaho Museum of Natural History collected material during the fall of 1966 and early summer of 1967. The following year, the Pacific Union College
in Angwin, California
conducted a small excavation. An unknown quantity of fossil material was removed prior to the establishment of the Hagerman Fossil Beds National Monument in 1988 (Richmond and others, 2002).
. Small mammalian fossil vertebrate genera include hare, weasel, gopher, vole and shrew. Also represented are fossil woodland birds, waterfowl, snakes, turtles, lizards, frogs, toads, salamanders and a variety of fish. Fossil bivalves and gastropods are also represented from the quarry (Richmond and others, 2002).
basin sediment
s that accumulated during the Miocene
through Pleistocene
Epoch
s. These clastic sedimentary
packages, interbedded with basalt
ic flows, pyroclastic tephra
and silicic
volcanic ash
es, have a cumulative thickness of 1524 meters (5000 feet), span about 10.5 Ma, and comprise the seven formations of the Idaho Group. The seven formations, in ascending order, are the Poison Creek, Branbury Basalt, Chalk Hills, Glenns Ferry, Tuana Gravel, Bruneau and Black Mesa Gravel (Richmond and others, 2002).
The Pliocene Glenns Ferry Formation spans 5.0 to 1.5 Ma. The formation
overlies the Branbury Basalt in the Hagerman area. The Glenns Ferry Formation is composed primarily of poorly consolidated lacustrine
and fluvial
sediments. The primary exposures of lacustrine sediments consist of laterally continuous very fine-grained sandstone and mudstone
beds that outcrop near Glenns Ferry, Idaho (47 km west of Hagerman, Idaho) (Richmond and others, 2002).
In the Hagerman Fossil Beds National Monument, the Glenns Ferry Formation has a maximum thickness of approximately 183 meters (600 feet) and spans the interval 4.5 to 3.0 Ma. The Glenns Ferry Formation consists of sandstones, siltstone
s, mudstones, and shale
s. Basaltic flows and deposits of basaltic tephra and ash of varying thicknesses are interbedded within the sedimentary strata
. Thin silicic
ash beds are also present. The formation is divided into three informal members based upon depositional facies
changes. The lower and middle members are delineated by the Peter's Gulch rhyolitic ash (age 3.7 Ma). The middle and upper members are separated by the Fossil Gulch dacite
ash (age 3.3 Ma) (Richmond and others, 2002).
Lithostratigraphically, the Hagerman Horse Quarry is located within the upper member of the Glenns Ferry Formation and lies 9.5 meters below the contact with the overlying Tuana Gravel. The Plio-Pleistocene Tuana Gravel unconformably overlies the Glenns Ferry Formation and is described as a series of cyclic beds of silt
, pebble sand
s and cobble gravel
. Sedimentological data of the Tuana Gravel indicates the gravel beds were deposited on a northwest sloping alluvial plain. Thickness of the gravel beds varies, but is about 50 feet in Fossil Gulch area. The Tuana Gravel is overlain by a caliche
, thought to have formed during a Pleistocene
interglacial
period, and several feet of recent soil
s (Richmond and others 2002).
. C. L. Gazin (1934) agreed with Gidley’s depositional interpretation, but suggested the bog
may have trapped the animals. Basing their conclusions on historical information, photographs, and collection samples, Akersten and Thompson (1992) proposed the fossil accumulation was the result of a single flood event, which trapped and killed the horses, then transported their carcasses
. They concluded that deposition
and burial
of the carcasses occurred during subsequent flood
ing events. Basing his interpretation on historical information and photographs coupled with a population configuration of ancient horse herds, G. McDonald (1996) suggested the horses were killed in a single catastrophic
flood
event.
The Hagerman Horse Quarry consists of three different fluvial sandstones. The Smithsonian Institution field crew excavated from all three quarry beds during the years 1929-1931 and 1934. The three sandstone beds are informally called the red, green, and white sandstone beds (Gazin, 1934). The Hagerman Fossil Beds National Monument reopened the Horse Quarry during the summer of 1997. The only sandstone now exposed within the monument is the white sandstone. The red and green sandstone remain covered by alluvium
(Richmond and others, 2002).
The white sandstone is a medium grained, poorly sorted, trough cross-bedded braided fluvial channel. Presently there is a longitudinal channel bar remaining in the quarry. The grain size indicates moderate paleoflow velocities with a paleocurrent direction to the south-southwest. All three quarry sandstones are interpreted to be ephemeral
braided fluvial channel systems that were deposited in the Snake River Plain graben
(Richmond and others, 2002).
and an ephemeral
flood. The Phase II drought on the Snake River Plain resulted in a mass mortality
of Equus simplicidens in addition to many other macro- and microvertebrates in the quarry area. The terrestrial animal
s were attracted to a drying pond or marsh, where they died of drought-induced starvation
, dehydration
, and illness. Decomposition
processes resulted in a substantial accumulation of disarticulated bones (i.e. bones of skeletons that are no longer joined together). Subsequently, an ephemeral flood traversed the dry paludal
deposit, transporting and depositing the bones. Geologic and taphonomic evidence indicates the bones traveled a very short distance prior to deposition and burial (Richmond and others, 2002).
The red sandstone bed, which stratigraphically underlies the white sandstone bed, also contains fossil material. The Smithsonian Institution excavated the majority of the Hagerman horse fossils from this bed during the 1930s. The taphonomic evidence of this bed indicates that a mass mortality of Equus simplicidens was the result of an earlier drought. The red sandstone bed was deposited under fluvial conditions similar to those evidenced in the white sandstone bed (Richmond and others, 2002).
Hagerman Horse
The Hagerman horse , also called the Hagerman zebra or the American zebra, was a North American species of equid from the Pliocene period and the Pleistocene period. It was one of the oldest horses of the genus Equus. Discovered in 1928 in Hagerman, Idaho, it is believed to have been like the...
fossils yet found. The quarry is within Hagerman Fossil Beds National Monument
Hagerman Fossil Beds National Monument
Hagerman Fossil Beds National Monument near Hagerman, Idaho, contains the largest concentration of Hagerman Horse fossils in North America. The fossil horses for which the Monument is famous have been found in only one locale in the northern portion of the Monument called the Hagerman Horse Quarry...
, located west of Hagerman, Idaho
Hagerman, Idaho
Hagerman is a town in Gooding County, Idaho, United States. The population was 768 at the 2007 census.-Geography:Hagerman is located at .According to the United States Census Bureau, the city has a total area of , all of it land....
, USA, at the geographic division of the Snake River
Snake River
The Snake is a major river of the greater Pacific Northwest in the United States. At long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean...
Plain. The Hagerman Horse Quarry is an integral part of the monument and is located on the northern flank of Fossil Gulch in the northern portion of the monument.
The Hagerman Horse Quarry resides near the top of the hillside of Smithsonian Hill. The hill was named from the early Smithsonian excavations of the Hagerman horse
Hagerman Horse
The Hagerman horse , also called the Hagerman zebra or the American zebra, was a North American species of equid from the Pliocene period and the Pleistocene period. It was one of the oldest horses of the genus Equus. Discovered in 1928 in Hagerman, Idaho, it is believed to have been like the...
(Equus simplicidens). The Hagerman Horse is the first fossil representation of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Equus
Equus (genus)
Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine...
in North America.
Historically, the Hagerman Horse Quarry was divided into three informal subquarries, the red, the green and white quarry sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s. Fossils are found throughout the monument; however the Horse Quarry continues to be the focus of paleontological research.
The Hagerman Fossil Beds National Monument visitor center is administered by the National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
. There is a skeleton reconstruction of a Hagerman Horse at the visitor center in Hagerman, Idaho. The Hagerman Fossil Beds National Monument reopened the Hagerman Horse Quarry during the summer of 1997. The Hagerman Horse Quarry is closed to visitors.
History
The Hagerman Horse Quarry has experienced a diverse collection history. Elmer Cook, a local rancher and resident of the area, first discovered fossil horse remains in the late 1920s. He reported the find to Dr. Harold T. Stearns of the United States Geological SurveyUnited States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
, who in turn brought it to the attention of Dr. James W. Gidley of the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
. The Smithsonian Institution field crew excavated from all three quarry beds during the years 1929-1931 and 1934 (Richmond and others, 2002).
The University of Utah
University of Utah
The University of Utah, also known as the U or the U of U, is a public, coeducational research university in Salt Lake City, Utah, United States. The university was established in 1850 as the University of Deseret by the General Assembly of the provisional State of Deseret, making it Utah's oldest...
, under the direction of Mr. Golden York, acquired fossils from the quarry in 1953. The Natural History Museum of Los Angeles County
Natural History Museum of Los Angeles County
The Natural History Museum of Los Angeles County opened in Exposition Park, Los Angeles, California, USA in 1913 as the Museum of History, Science, and Art. The moving force behind it was a museum association founded in 1910. Its distinctive main building, with fitted marble walls and domed and...
managed their excavation during the summer of 1966. The Idaho Museum of Natural History collected material during the fall of 1966 and early summer of 1967. The following year, the Pacific Union College
Pacific Union College
Pacific Union College is a private, coeducational liberal arts college located in Angwin, California, United States. It is the only four-year college in Napa County, California....
in Angwin, California
Angwin, California
Angwin is a census-designated place in Napa County, United States. California. It is part of the northern San Francisco Bay Area. The population was 3,051 at the 2010 census. Its area code is 707. Its two zip codes are 94508 and 94576. It is in the Pacific time zone.The town was named in 1874 for...
conducted a small excavation. An unknown quantity of fossil material was removed prior to the establishment of the Hagerman Fossil Beds National Monument in 1988 (Richmond and others, 2002).
Quarry fossils
Based on the documented number of skulls collected from the Hagerman Horse Quarry, at least 200 Hagerman horses are represented from the quarry. Besides the fossil horse, Equus simplicidens, other large vertebrates collected from the quarry include an antelope, a camel and a peccaryPeccary
A peccary is a medium-sized mammal of the family Tayassuidae, or New World Pigs. Peccaries are members of the artiodactyl suborder Suina, as are the pig family and possibly the hippopotamus family...
. Small mammalian fossil vertebrate genera include hare, weasel, gopher, vole and shrew. Also represented are fossil woodland birds, waterfowl, snakes, turtles, lizards, frogs, toads, salamanders and a variety of fish. Fossil bivalves and gastropods are also represented from the quarry (Richmond and others, 2002).
Quarry stratigraphy
The western Snake River Plain consists of riftRift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
basin sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s that accumulated during the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
through Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
Epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...
s. These clastic sedimentary
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
packages, interbedded with basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic flows, pyroclastic tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
and silicic
Silicic
Silicic is a term used to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually put at at least 65 percent. Granite and rhyolite are typical silicic rocks....
volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
es, have a cumulative thickness of 1524 meters (5000 feet), span about 10.5 Ma, and comprise the seven formations of the Idaho Group. The seven formations, in ascending order, are the Poison Creek, Branbury Basalt, Chalk Hills, Glenns Ferry, Tuana Gravel, Bruneau and Black Mesa Gravel (Richmond and others, 2002).
The Pliocene Glenns Ferry Formation spans 5.0 to 1.5 Ma. The formation
Formation
Formation may refer to:* Formation flying, aerobatics performed with several aircraft* Formation , a high-level military organization* Tactical formation, the physical deployment of military forces-Sports:...
overlies the Branbury Basalt in the Hagerman area. The Glenns Ferry Formation is composed primarily of poorly consolidated lacustrine
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
and fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
sediments. The primary exposures of lacustrine sediments consist of laterally continuous very fine-grained sandstone and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
beds that outcrop near Glenns Ferry, Idaho (47 km west of Hagerman, Idaho) (Richmond and others, 2002).
In the Hagerman Fossil Beds National Monument, the Glenns Ferry Formation has a maximum thickness of approximately 183 meters (600 feet) and spans the interval 4.5 to 3.0 Ma. The Glenns Ferry Formation consists of sandstones, siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
s, mudstones, and shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s. Basaltic flows and deposits of basaltic tephra and ash of varying thicknesses are interbedded within the sedimentary strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
. Thin silicic
Silicic
Silicic is a term used to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually put at at least 65 percent. Granite and rhyolite are typical silicic rocks....
ash beds are also present. The formation is divided into three informal members based upon depositional facies
Facies
In geology, facies are a body of rock with specified characteristics. Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment....
changes. The lower and middle members are delineated by the Peter's Gulch rhyolitic ash (age 3.7 Ma). The middle and upper members are separated by the Fossil Gulch dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
ash (age 3.3 Ma) (Richmond and others, 2002).
Lithostratigraphically, the Hagerman Horse Quarry is located within the upper member of the Glenns Ferry Formation and lies 9.5 meters below the contact with the overlying Tuana Gravel. The Plio-Pleistocene Tuana Gravel unconformably overlies the Glenns Ferry Formation and is described as a series of cyclic beds of silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
, pebble sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
s and cobble gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
. Sedimentological data of the Tuana Gravel indicates the gravel beds were deposited on a northwest sloping alluvial plain. Thickness of the gravel beds varies, but is about 50 feet in Fossil Gulch area. The Tuana Gravel is overlain by a caliche
Caliche (Mineral)
Caliche is a sedimentary rock, a hardened deposit of calcium carbonate. This calcium carbonate cements together other materials, including gravel, sand, clay, and silt. It is found in aridisol and mollisol soil orders...
, thought to have formed during a Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
period, and several feet of recent soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s (Richmond and others 2002).
Quarry deposition
Dr. James W. Gidley (1930) originally interpreted the Smithsonian fossiliferous red sandstone bed to have been deposited in a bog or water hole. Death of the animals, he thought, was the result of attritionAttrition
Attrition may refer to:*Physical wear*Attrition warfare, the military strategy of wearing down the enemy by continual losses in personnel and material*Loss of personnel by Withdrawal...
. C. L. Gazin (1934) agreed with Gidley’s depositional interpretation, but suggested the bog
Bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....
may have trapped the animals. Basing their conclusions on historical information, photographs, and collection samples, Akersten and Thompson (1992) proposed the fossil accumulation was the result of a single flood event, which trapped and killed the horses, then transported their carcasses
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
. They concluded that deposition
Deposition (geology)
Deposition is the geological process by which material is added to a landform or land mass. Fluids such as wind and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of...
and burial
Burial
Burial is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over.-History:...
of the carcasses occurred during subsequent flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing events. Basing his interpretation on historical information and photographs coupled with a population configuration of ancient horse herds, G. McDonald (1996) suggested the horses were killed in a single catastrophic
Catastrophic failure
A catastrophic failure is a sudden and total failure of some system from which recovery is impossible. Catastrophic failures often lead to cascading systems failure....
flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
event.
The Hagerman Horse Quarry consists of three different fluvial sandstones. The Smithsonian Institution field crew excavated from all three quarry beds during the years 1929-1931 and 1934. The three sandstone beds are informally called the red, green, and white sandstone beds (Gazin, 1934). The Hagerman Fossil Beds National Monument reopened the Horse Quarry during the summer of 1997. The only sandstone now exposed within the monument is the white sandstone. The red and green sandstone remain covered by alluvium
Alluvium
Alluvium is loose, unconsolidated soil or sediments, eroded, deposited, and reshaped by water in some form in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel...
(Richmond and others, 2002).
The white sandstone is a medium grained, poorly sorted, trough cross-bedded braided fluvial channel. Presently there is a longitudinal channel bar remaining in the quarry. The grain size indicates moderate paleoflow velocities with a paleocurrent direction to the south-southwest. All three quarry sandstones are interpreted to be ephemeral
Ephemeral
Ephemeral things are transitory, existing only briefly. Typically the term is used to describe objects found in nature, although it can describe a wide range of things....
braided fluvial channel systems that were deposited in the Snake River Plain graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
(Richmond and others, 2002).
Taphonomy
The white sandstone accumulation, consisting of hundreds of bones, resulted from a moderate droughtDrought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
and an ephemeral
Ephemeral
Ephemeral things are transitory, existing only briefly. Typically the term is used to describe objects found in nature, although it can describe a wide range of things....
flood. The Phase II drought on the Snake River Plain resulted in a mass mortality
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
of Equus simplicidens in addition to many other macro- and microvertebrates in the quarry area. The terrestrial animal
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
s were attracted to a drying pond or marsh, where they died of drought-induced starvation
Starvation
Starvation is a severe deficiency in caloric energy, nutrient and vitamin intake. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, death...
, dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
, and illness. Decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
processes resulted in a substantial accumulation of disarticulated bones (i.e. bones of skeletons that are no longer joined together). Subsequently, an ephemeral flood traversed the dry paludal
Paludal
Paludal is derived from the Latin word palus .*Paludal, in geology, refers to sediments that accumulated in a marsh environment.*Paludal, in ecology, refers to the environment of a marsh.----...
deposit, transporting and depositing the bones. Geologic and taphonomic evidence indicates the bones traveled a very short distance prior to deposition and burial (Richmond and others, 2002).
The red sandstone bed, which stratigraphically underlies the white sandstone bed, also contains fossil material. The Smithsonian Institution excavated the majority of the Hagerman horse fossils from this bed during the 1930s. The taphonomic evidence of this bed indicates that a mass mortality of Equus simplicidens was the result of an earlier drought. The red sandstone bed was deposited under fluvial conditions similar to those evidenced in the white sandstone bed (Richmond and others, 2002).