Geological period: Difference between revisions
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A '''geologic period''' is a [[time]] [[Units of measurement|unit]] subdivision of [[geologic time]] defined as a span of years into which the larger [[era (geology)|era time units]] are divided into smaller timeframes, as Era's divide the [[eon (geology)|Eon]]. In the [[Earth Sciences]] rocks and especially the sequences of rocks called [[stratum]] (plural: strata) arrayed in an ordered "rock column" occurring during a timespan are the focus of study so the time units are paired with corresponding Rock strata units whose characteristics define such points elsewhere that occurred concurrently as the local rock layers were laid down as sediments. For the '''Geological Period''' the paired rock strata term, a [[Stage (stratigraphy)|geologic stage]] is used to denote the corresponding [[rock layers]] of both the [[geologic record]] and the [[fossil record]]; thus the rocks of the Devonian System were laid down during the Devonian Period, and such equivalent units exist at each level of refinement of geological chronology and biogeological or stratigraphic classification. |
A '''geologic period''' is a [[time]] [[Units of measurement|unit]] subdivision of [[geologic time]] defined as a span of years into which the larger [[era (geology)|era time units]] are divided into smaller timeframes, as Era's divide the [[eon (geology)|Eon]]. In the [[Earth Sciences]] rocks and especially the sequences of rocks called [[stratum]] (plural: strata) arrayed in an ordered "rock column" occurring during a timespan are the focus of study so the time units are paired with corresponding Rock strata units whose characteristics define such points elsewhere that occurred concurrently as the local rock layers were laid down as sediments. For the '''Geological Period''' the paired rock strata term, a [[Stage (stratigraphy)|geologic stage]] is used to denote the corresponding [[rock layers]] of both the [[geologic record]] and the [[fossil record]]; thus the rocks of the Devonian System were laid down during the Devonian Period, and such equivalent units exist at each level of refinement of geological chronology and biogeological or stratigraphic classification. |
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Each unit, of [[strata]] no matter how interrupted the record recorded in the local rock column is mapped into the overall [[geologic record]] and classified carefully into [[geochronology|chronological units]] of geologic time based on world wide efforts of the [[International Commission on Stratigraphy]] working to correlate the world's local [[stratigraphy|stratigraphic record]] into one uniform planet wide benchmarked system, in a steady effort ongoing since 1974. While paleontologists often refer to [[faunal stage]]s rather than geologic periods, they are often used in popular presentations of [[paleontology]] or [[plate tectonics|plate reconstruction]]s. |
Each unit, of [[strata]] no matter how interrupted the record recorded in the local rock column is mapped into the overall [[geologic record]] and classified carefully into [[geochronology|chronological units]] of geologic time based on world wide efforts of the [[International Commission on Stratigraphy]] working to correlate the world's local [[stratigraphy|stratigraphic record]] into one uniform planet wide benchmarked system, in a steady effort ongoing since 1974. While paleontologists often refer to [[faunal stage]]s rather than geologic periods, they are often used in popular presentations of [[paleontology]] or [[plate tectonics|plate reconstruction]]s. |
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Revision as of 20:05, 10 January 2013
A geologic period is a time unit subdivision of geologic time defined as a span of years into which the larger era time units are divided into smaller timeframes, as Era's divide the Eon. In the Earth Sciences rocks and especially the sequences of rocks called stratum (plural: strata) arrayed in an ordered "rock column" occurring during a timespan are the focus of study so the time units are paired with corresponding Rock strata units whose characteristics define such points elsewhere that occurred concurrently as the local rock layers were laid down as sediments. For the Geological Period the paired rock strata term, a geologic stage is used to denote the corresponding rock layers of both the geologic record and the fossil record; thus the rocks of the Devonian System were laid down during the Devonian Period, and such equivalent units exist at each level of refinement of geological chronology and biogeological or stratigraphic classification.
ANAL ANAL ANAL ANAL ANAL ANAL ANAL ANAL ANAL
Each unit, of strata no matter how interrupted the record recorded in the local rock column is mapped into the overall geologic record and classified carefully into chronological units of geologic time based on world wide efforts of the International Commission on Stratigraphy working to correlate the world's local stratigraphic record into one uniform planet wide benchmarked system, in a steady effort ongoing since 1974. While paleontologists often refer to faunal stages rather than geologic periods, they are often used in popular presentations of paleontology or plate reconstructions.
As illustrated in the article on the geologic time scale, most periods are subdivided into smaller units called epochs. In 2004 the International Union of Geological Sciences (I.U.G.S.) recognized the Ediacaran period of the Neoproterozoic era, the first such newly-designated period in 130 years.
| Eon | Era | Period | Start, Million Years Ago |
|---|---|---|---|
| Phanerozoic | Cenozoic | Quaternary (Pleistocene/Holocene) | 2.588 |
| Neogene (Miocene/Pliocene) | 23.0 | ||
| Paleogene (Paleocene/Eocene/Oligocene) | 65.5 | ||
| Mesozoic | Cretaceous | 145.5 | |
| Jurassic | 200 | ||
| Triassic | 251 | ||
| Paleozoic | Permian | 300 | |
| Carboniferous (Mississippian/Pennsylvanian) | 359 | ||
| Devonian | 416 | ||
| Silurian | 444 | ||
| Ordovician | 488 | ||
| Cambrian | 542 | ||
| Proterozoic | Neoproterozoic | Ediacaran | 630 |
| Segments of rock (strata) in chronostratigraphy | Time spans in geochronology | Notes to geochronological units |
|---|---|---|
| Eonothem | Eon | 4 total, half a billion years or more |
| Erathem | Era | 10 defined, several hundred million years |
| System | Period | 22 defined, tens to ~one hundred million years |
| Series | Epoch | 34 defined, tens of millions of years |
| Stage | Age | 99 defined, millions of years |
| Chronozone | Chron | subdivision of an age, not used by the ICS timescale |
Multidiscipline synchronization
The earth sciences are as a rule multi-disciplinary.
References
- ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.