Erathem
Encyclopedia
| Eras and Erathems mapped into Eons | ||
| Eras and Erathems in the Phanerozoic Phanerozoic The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared... Eon |
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| Geologic Era | Span of Years | Notes: |
| 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... |
many GSSP points | |
| Mesozoic Mesozoic The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time... |
many GSSP points | |
| Paleozoic Paleozoic The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly... |
mostly GSSP points | |
| Eras and Erathems in the Proterozoic Proterozoic The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"... Eon 542.0 (+/- 1.0) Mya — 2500 Mya |
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| Neoproterozoic Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods... |
few GSSP points | |
| Mesoproterozoic Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them... |
all GSSA points | |
| Paleoproterozoic Paleoproterozoic The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized... |
all GSSA points | |
| Eras and Erathems in the Archean Archean The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically... Eon 2500 Mya — years > 3600 Mya rocks older than 2.5 Billion 1000000000 (number) 1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109.... years — rocks older than 3.6 Billion years |
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| Neoarchean Neoarchean The Neoarchean is a geologic era within the Archaean. It spans the period of time from —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth... |
(only GSSA points) | |
| Mesoarchean Mesoarchean The Mesoarchean is a geologic era within the Archean, spanning 3200 Ma to 2800 Ma . The period is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have lived on Earth since the Mesoarchean. The Pongola... |
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| Paleoarchean Paleoarchean The Paleoarchean is a geologic era within the Archaean. It spans the period of time 3600 Ma to 3200 Ma —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. The oldest ascertained life form is from this period.... |
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| Eoarchean Eoarchean In the geologic record the Eoarchean erathem and the Eoarchean era in the geologic timescale correspond to one another in the dual system of classification of rock strata laid down beginning 4000 Ma to 3600 Ma .- Chronology :It was formerly officially unnamed and usually referred to as the first... |
Earth 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... |
Earth's crust solidifies ca 3800 Mya |
| Note: Rocks older than ca. 2500 Mya old are rare due to tectonic activity Tectonics Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of... recycling the earths crust. |
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In stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
, paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
, and geobiology
Geobiology
Broadly defined, geobiology is an interdisciplinary field of scientific research that explores interactions between the biosphere and the lithosphere and/or the atmosphere....
an erathem is the total stratigraphic
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
record deposited during a certain corresponding span of time, an era in the geologic timescale.
It can therefore be used as a chronostratigraphic
Chronostratigraphy
Chronostratigraphy is the branch of stratigraphy that studies the age of rock strata in relation to time.The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of...
unit of time which delineates a large span of years — less than an geological eon, but greater than its successively smaller and more refined subdivisions (geologic periods, epochs
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
, and geologic ages). By 3,500 Million years ago (Mya) simple life had developed on earth (the oldest known microbial fossils in Australia are dated to this figure.
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, Ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, Sulphur compounds, etc.— a so called reducing atmosphere
Reducing atmosphere
A reducing atmosphere, also known as a reduction atmosphere, is an atmospheric condition in which oxidation is prevented by removal of oxygen and other oxidising gases or vapours. Usually nitrogen is used or in more extreme conditions hydrogen gas. In that case the atmosphere is reducing...
lacking much free oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
which was bound up in compounds).
These simple organisms, Cyanobacteria ruled the still cooling earth for approximately a thousand million (over a billion) years and gradually transformed the atmosphere to one containing free oxygen. These changes, along with tectonic activity
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
left chemical trails (red bed formation, etc.) and other physical clues (magnetic orientation, layer formation factors) in the rock record, and it is these changes along with the later richer fossil record which specialists use to demarcate times early in planet earth's history in various disciplines.
Erathems are not often used in practice. While they are subdivisions of eonothem
Eonothem
In stratigraphy and geology, an eonothem is the totality of rock strata laid down in the stratigraphic record deposited during a certain eon of the continuous geologic timescale...
s and are themselves subdivided into systems
System (geology)
A system in the natural sciences and stratigraphy is an idealized composite unit of the geologic record made up of a succession of rock layers that were laid down together within a certain corresponding geological time span, and are used in turn to date things to a certain corresponding geologic...
, dating experts prefer the finer resolution of smaller spans of time when evaluating strata.
Erathems have the same names as their corresponding eras.
- The Phanerozoic eonothem can thus be divided into a
- CenozoicCenozoicThe 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...
, a MesozoicMesozoicThe Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and a PaleozoicPaleozoicThe Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
erathem or matching era name.
- Cenozoic
Similarly, the Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
eonothem is divided youngest to oldest into the
-
- NeoproterozoicNeoproterozoicThe Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
, MesoproterozoicMesoproterozoicThe Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...
and PaleoproterozoicPaleoproterozoicThe Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
erathems,
- Neoproterozoic
- and the ArcheanArcheanThe Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
eon and eonothem are divided similarly into the- NeoarcheanNeoarcheanThe Neoarchean is a geologic era within the Archaean. It spans the period of time from —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth...
, MesoarcheanMesoarcheanThe Mesoarchean is a geologic era within the Archean, spanning 3200 Ma to 2800 Ma . The period is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have lived on Earth since the Mesoarchean. The Pongola...
, PaleoarcheanPaleoarcheanThe Paleoarchean is a geologic era within the Archaean. It spans the period of time 3600 Ma to 3200 Ma —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. The oldest ascertained life form is from this period....
and the EoarcheanEoarcheanIn the geologic record the Eoarchean erathem and the Eoarchean era in the geologic timescale correspond to one another in the dual system of classification of rock strata laid down beginning 4000 Ma to 3600 Ma .- Chronology :It was formerly officially unnamed and usually referred to as the first...
, for which a lower (oldest) limit is undefined.
- Neoarchean
Related other topics
- Body form
- European Mammal Neogene
- Geologic time scaleGeologic time scaleThe geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
- New Zealand geologic time scaleNew Zealand geologic time scaleWhile also using the international Geologic time scale, many nations - especially those with isolated and therefore non-standard prehistories - use their own system of dividing geologic time into epochs and faunal stages....
- New Zealand geologic time scale
- North American Land Mammal Age
- Fauna (animals)
- Type localityType locality (geology)Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
- List of GSSPs
External links
- The Global Boundary Stratotype Section and Point (GSSP): overview
- Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart
- Geotime chart displaying geologic time periods compared to the fossil record - Deals with chronology and classifications for laymen (not GSSPs)