North American Land Mammal Ages
Encyclopedia
The North American Mammal Ages (NALMA) establishes a geologic timescale for prehistoric North America
n fauna beginning 66.5 Ma during the Paleocene
and continuing through to the Late Pleistocene
(0.11 Ma). These periods are referred to as ages, stages, or intervals and were established using geographic place names where fossil
materials were obtained.
Cenozoic
record of North America and was the source for similar time scales dealing with other continents. The system was revised into a formal chronostratigraphic system. This approach is nominally justified by international stratigraphic codes; it holds that first appearances of individual species
in particular sections are the only valid basis for naming and defining the land-mammal ages.
The basic unit of measure is the first/last boundary statement. This shows that the first appearance event of one taxon
is known to predate the last appearance event of another. If two taxa are found in the same fossil quarry
or at the same stratigraphic horizon, then their age-range zones overlap.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n fauna beginning 66.5 Ma during the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
and continuing through to the Late Pleistocene
Late Pleistocene
The Late Pleistocene is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of the Eemian interglacial phase before the final glacial episode of the Pleistocene 126,000 ± 5,000 years ago. The end of the stage is defined exactly at 10,000 Carbon-14 years BP...
(0.11 Ma). These periods are referred to as ages, stages, or intervals and were established using geographic place names where fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
materials were obtained.
System
The North American Land-Mammal Age system was formalized in 1941 as a series of provincial land-mammal ages. The system was the standard for correlations in the terrestrialEarth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
record of North America and was the source for similar time scales dealing with other continents. The system was revised into a formal chronostratigraphic system. This approach is nominally justified by international stratigraphic codes; it holds that first appearances of individual species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in particular sections are the only valid basis for naming and defining the land-mammal ages.
The basic unit of measure is the first/last boundary statement. This shows that the first appearance event of one taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
is known to predate the last appearance event of another. If two taxa are found in the same fossil quarry
Quarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
or at the same stratigraphic horizon, then their age-range zones overlap.
Ages
- RancholabreanRancholabreanThe Rancholabrean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from less than 240,000 years to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene...
: Lower boundary ~0.24 Ma. Upper boundary 0.011 Ma. - IrvingtonianIrvingtonianThe Irvingtonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 1,800,000 to 300,000 years BP, a period of . It is usually considered to overlap the Lower Pleistocene and Middle...
: Lower boundary 1.8 Ma. Upper boundary ~0.24 Ma. - BlancanBlancanThe Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
: Lower boundary 4.9 Ma. Upper boundary 1.8 Ma. - HemphillianHemphillianThe Hemphillian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
: Lower boundary 10.3 Ma Upper boundary 4.9 Ma. - ClarendonianClarendonianThe Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 13,600,000 to 10,300,000 years BP, a period of . It is usually considered to overlap the Serravallian of the Middle...
: Lower boundary 13.6 Ma. Upper boundary 10.3 Ma. - BarstovianBarstovianThe Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 16,300,000 to 13,600,000 years BP, a period of . It is usually considered to overlap the Langhian and Serravallian...
: Lower boundary 16.3 Ma. Upper boundary 13.6 Ma. - Hemingfordian: Lower boundary 20.6 Ma. Upper boundary 16.3 Ma.
- Late HemingfordianLate HemingfordianThe Late Hemingfordian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 20,430,000 to 16,300,000 years BP, a period of . It is usually considered to overlap the Early Miocene...
Lower boundary 20.4 Ma. Upper boundary 16.3 Ma.
- Late Hemingfordian
- ArikareeanArikareeanThe Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usually considered to overlap the Oligocene and Miocene epochs...
: Lower boundary 30.8 Ma. Upper boundary 20.6 Ma. - GeringianGeringianThe Geringian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 30,800,000 to 26,300,000 years BP, a period of . It is usually considered to fall within the Oligocene epoch...
: Lower boundary 30.8 Ma. Upper boundary 26.3 Ma. - WhitneyanWhitneyanThe Whitneyan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 33,300,000 to 30,800,000 years BP, a period of . It is usually considered to fall within the Early Oligocene...
: Lower boundary 33.3 Ma. Upper boundary 30.8 Ma. - OrellanOrellanThe Orellan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 33,900,000 to 33,300,000 years BP, a period of . It is usually considered to fall within the Early Oligocene...
: Lower boundary 33.9 Ma. Upper boundary 33.3 Ma. - ChadronianChadronianThe Chadronian age within the North American Land Mammal Ages chronology is the North American faunal stage typically set from 38,000,000 to 33,900,000 years BP, a period of . It is usually considered to fall within the Eocene epoch...
: Lower boundary Upper 38 Ma. boundary 33.9 Ma. - DuchesneanDuchesneanThe Duchesnean North American Stage on the geologic timescale is a North American Land Mammal Age , with an age from 42 to 38 million years BP, representing . It falls within the Eocene epoch. The Duchesnean is preceded by the Uintan and followed by the Chadronian NALMA.The Duchesnean falls within...
: Lower boundary 42 Ma. Upper boundary 38 Ma. - UintanUintanThe Uintan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 46,200,000 to 42,000,000 years BP lasting . It is usually considered to fall within the Eocene epoch...
: Lower boundary 46.2 Ma. Upper boundary 42 Ma. - Bridgerian: Lower boundary 50.3 Ma. Upper boundary 46.2 Ma.
- WasatchianWasatchianThe Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 55,400,000 to 50,300,000 years BP lasting . It is usually considered to be within the Eocene, more specifically the...
: Lower boundary 55.4 Ma. Upper boundary 50.3 Ma. - ClarkforkianClarkforkianThe Clarkforkian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 56,800,000 to 55,400,000 years BP lasting . It is usually considered to be within the Paleocene, more specifically the...
: Lower boundary 56.8 Ma. Upper boundary 55.4 Ma. - TiffanianTiffanianThe Tiffanian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 60,200,000 to 56,800,000 years BP lasting . It is usually considered to overlap the Selandian and Thanetian within the...
: Lower boundary 60.2 Ma. Upper boundary 56.8 Ma. - TorrejonianTorrejonianThe Torrejonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 63,300,000 to 60,200,000 years BP lasting . It is usually considered to overlap the Selandian and Thanetian within the...
: Lower boundary 63.3 Ma. Upper boundary 60.2 Ma. - PuercanPuercanThe Puercan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 65,000,000 to 63,300,000 years BP lasting . It is usually considered to be within the Paleocene...
: Lower boundary 66.5 Ma Upper boundary 63.3 Ma.
Other continental ages
- European Land Mammal Age
- South American Land Mammal AgeSouth American Land Mammal AgeThe South American Mammal Ages establish a geologic timescale for prehistoric South American fauna beginning 64.5 Ma during the Paleogene and continuing through to the Middle Pleistocene...
- Asian Land Mammal Age