|
Whitneyan
The Whitneyan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), 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. The Whitneyan is preceded by the Orellan and followed by the Arikareean NALMA stages. The Whitneyan is interchangeable with the Rupelian The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ... age. References Oligocene life Oligocene animals of North America {{geochronology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orellan
The Orellan is a North American Land Mammal Age typically set from around 33,700,000 to 32,000,000 years BP, a period of . The Orellan is preceded by the Chadronian and followed by the Whitneyan NALMA stages. Relative to global geological chronology (the geologic time scale), it is usually considered to fall within the earliest part (early Rupelian stage) of the Oligocene epoch, beginning around the same time as the Eocene-Oligocene boundary. The Orellan is named after the Orella Member of the Brule Formation, a widespread subunit of the White River Group. The Orella Member crops out most extensively in northwest Nebraska and eastern Wyoming. In the White River badlands of southwest South Dakota, an equally extensive Orellan component of the Brule Formation is known as the Scenic Member. Orellan strata of the Brule Formation can be found in more restricted exposures across northeast Colorado (Cedar Creek Member) and North Dakota. Certain sites in Montana preserve Orellan mammals: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Land Mammal Ages
The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when referring to the rock strata of that age) and were established using geographic place names where fossil 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 terrestrial 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/las ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Oligocene
The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian Stage. Name The stage is named after the small river Rupel in Belgium, a tributary to the Scheldt. The Belgian Rupel Group derives its name from the same source. The name Rupelian was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850. The separation between the group (stratigraphy), group and the stage was made in the second half of the 20th century, when stratigraphers saw the need to distinguish between lithostratigraphy, lithostratigraphic and chronostratigraphy, chronostratigraphic names. Stratigraphic definition The base of the Rupelian Stage (which is also the base of the Oligocene Series) is at the extinction of the foram ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arikareean
The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), 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 The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ... epochs. The Arikareean is preceded by the Whitneyan and followed by the Hemingfordian NALMA stages. The Arikareean can be further divided into the substages of: *late Late Arikareean: Lower boundary source, base of Geringian (approximate) *early Late Arikareean: base of Geringian (approximate). Upper boundary source: base of Hemingfordian (approximate). *late Early Arikareean: Lower boundary source of base of Geringian (approximate). Upp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rupelian
The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian Stage. Name The stage is named after the small river Rupel in Belgium, a tributary to the Scheldt. The Belgian Rupel Group derives its name from the same source. The name Rupelian was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850. The separation between the group (stratigraphy), group and the stage was made in the second half of the 20th century, when stratigraphers saw the need to distinguish between lithostratigraphy, lithostratigraphic and chronostratigraphy, chronostratigraphic names. Stratigraphic definition The base of the Rupelian Stage (which is also the base of the Oligocene Series) is at the extinction of the foram ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geologic Timescale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faunal Stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries. Rock series are divided into stages, just as geological epochs are divided into ages. Stages are divided into smaller stratigraphic units called chronozones or substages, and added together into superstages. The term faunal stage is sometimes used, referring to the fact that the same fauna (animals) are found throughout the layer (by definition). Definition Stages are primarily defined by a consistent set of fossils ( biostratigraphy) or a consistent magnetic polarity (see paleomagnetism) in the rock. Usually one or more index fossils that are common, found worldwide, easily recognized, and limited to a single, or at most a few, stages are used to define the stage's bottom. Thus, f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Before Present
Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1January 1950 as the commencement date (epoch) of the age scale, with 1950 being labelled as the "standard year". The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must account for when using radiocarbon dating for dates of origin that may fall after this year. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation "RCYBP" stands for the explicit "radio carbon years before present". Usage The BP scale is s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligocene Life
The Oligocene ( ) is a geologic epoch of the Paleogene Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from Ancient Greek (''olígos'') 'few' and (''kainós'') 'new', and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period. The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included a global expansion of g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
