The Cenozoic (sen-oh-ZOH-ik; meaning "new life" (Greek: kainos = new + zoe = life)), sometimes Caenozoic in the United Kingdom, is the third and ongoing era of the Phanerozoic eon, corresponding to the Cenozoic erathem of the Phanerozoic eonothem. It covers the 66 million years since the Cretaceous-Tertiary extinction event at the end of the Maastrichtian age of the Cretaceous that marked the demise of the last ammonites, sauropterygians, pterosaurs and non-avian dinosaurs. During Cenozoic, mammals and birds (avian dinosaurs) reached great diversity. At the end of the Eocene epoch, the new glaciation began for the first time since the Permian period. This glaciation continues now, but under the influence of the activities of Homo sapiens, the ice masses at both poles are melting at an accelerated pace.
Definition[]
Wyoming rock wich with the Iridium geochemical anomaly (light intermediate claystone layer), that indicates the base of the Cenozoic erathem.
The Global Stratotype Section and Point (GSSP) of the Cenozoic erathem as well as the Paleogene system, the Paleocene series and the Danian stage was ratified in 1991. The base of the erathem is defined in Oued Djerfane, Tunisia, and related to the Iridium geochemical anomaly. It also associated with a major horizon of the K-Pg extinction event.[1] Most of the Cenozoic GSSPs were established in the Mediterranean region.
Subdivisions[]
The Cenozoic era is divided into three periods, the Paleogene, the Neogene, and the Quaternary. Periods are divided into epochs. The Palaeogene consists of the Paleocene, Eocene, and Oligocene epochs, the Neogene consists of the Miocene and Pliocene epochs, and the Quaternary consists of the Pleistocene and Holocene epochs, the last of which is ongoing. Each epoch including Holocene in turn divided into ages.
Historically, the Cenozoic has been divided into periods (or sub-eras) named the Tertiary (Paleocene to Pliocene) and Quaternary (Pleistocene and Holocene), although most geologists no longer recognize the Tertiary.
At the beginning of the 21st century, a new, youngest geological epoch within the Cenozoic, was proposed. This epoch, called the Anthropocene, was proposed to be counted from 1950 AD, the conventional beginning of the atomic age. However, in 2024, the Subcommission on Quaternary Stratigraphy (SQS) rejected a proposal to designate the Anthropocene as a new epoch.
North America[]
The North American Land Mammal Ages (NALMAs) and their correlation with the Cenozoic epochs. ka = thousand years ago, Ma = million years ago.
In North America, many regional units, known as North American Land Mammal Ages (NALMAs), are also used. NALMAs are very different from international epochs (series) and ages (stages) of the Cenozoic. These units applies only to terrestrial mammals in fossil record and there are 21 NALMAs in comparison to 24 stages of IUGS. The youngest NALMA, Saintaugustinean, began in 1540, making it much shorter than any international subdivision of the Holocene.
NALMAs from upper to lower with lower boundary age in brackets:
- Saintaugustinean (1540 AD)
- Santarosean (14 ka)
- Rancholabrean (210 ka)
- Irvingtonian (1.4 Ma)
- Blancan (4.7 Ma)
- Hemphillian (9.4 Ma)
- Clarendonian (12.5 Ma)
- Barstovian (16.3 Ma)
- Hemingfordian (18.5 Ma)
- Arikareean (29.5 Ma)
- Whitneyan (31.8 Ma)
- Orellan (33.9 Ma)
- Chadronian (37.0 Ma)
- Duchesnean (39.7 Ma)
- Uintan (46.2 Ma)
- Bridgerian (50.5 Ma)
- Wasatchian (54.9 Ma)
- Clarkforkian (56.2 Ma)
- Tiffanian (60.9 Ma)
- Torrejonian (63.8 Ma)
- Puercan (66 Ma)
Tectonics[]
Geologically, the Cenozoic is the era when continents moved into their current positions. Australia-New Guinea split from Gondwana to drift north and, eventually, abut South-east Asia; Antarctica moved into its current position over the South Pole; the Atlantic Ocean widened and, later in the era, South America became attached to North America.
Life in the Cenozoic Era[]
The Cenozoic is the age of mammal. During the Cenozoic, mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals. The Cenozoic is just as much the age of savannas, or the age of co-dependent flowering plants and insects. Birds which remained the only surviving dinosaur group, also evolved substantially in the Cenozoic.
See also[]
- Geologic Time Scale
References[]
Further reading[]
- British Caenozoic Fossils, 1975, The Natural History Museum, London.