System (period) | Series | Stage (age) | Lower boundary, Ma | |
---|---|---|---|---|
Quaternary | Holocene | Meghalayan | 0.0042 | |
Northgrippian | 0.0082 | |||
Greenlandian | 0.0117 | |||
Pleistocene | Upper | 0.129 | ||
Chibanian | 0.774 | |||
Calabrian | 1.80 | |||
Gelasian | 2.58 | |||
Neogene | Pliocene | Piacenzian | older | |
Subdivisions and "golden spikes" according to IUGS as of September 2023[1] |
Quaternary is the current and most recent of the three periods of the Cenozoic era, corresponding to the Quaternary system in stratigraphy. It follows the Neogene period and spans from 2.58 million years ago to the present. It is the shortest period of the Phanerozoic eon and is approximately seven times shorter than the Norian age of the Triassic. It is characterized by glaciations in the northern hemisphere (for this reason it is often called the ice age), after which a new global warming began. During the Quaternary, humans appeared and spread, creating civilization and causing the Holocene mass extinction.
Definition[]
The Global Stratotype Section and Point (GSSP) of the Quaternary system, the Pleistocene series and the Gelasian stage was ratified in 2009. The lower boundary is defined in the section on Sicily, Italy, and related to the base of marly layer overlying sapropel MPRS 250.[2]
Subdivisions[]
The Quaternary system is divided into the Pleistocene and Holocene series, corresponding to the epochs of the same names in stratigraphy. Both Pleistocene and Holocene include several stages that correspond to the ages of the same name in geochronology.
Anthropocene[]
At the beginning of the twenty-first century, there was a proposal to distinguish another geological epoch, the Anthropocene, with a start date around 1950, when humans began to use nuclear weapons that could change landscapes. The Anthropocene Working Group (AWG) of the Subcommission on Quaternary Stratigraphy (SQS) spent several years searching for a suitable site for establishing the GSSP. The researchers proposed 12 places with corresponding names for the first age/stage of the new epoch/series and various dates for its beginning.[3] In July 2023, Crawford Lake in Canada was suggested.[4] In 2024, the Anthropocene was rejected by the International Union of Geological Sciences (IUGS) for inclusion in the Geologic Time Scale, but, as stated in the explanation, "it will remain an invaluable descriptor in human-environment interactions. But it will not be recognised as a formal geological term but will more usefully be employed informally in future discussions of the anthropogenic impacts on Earth’s climatic and environmental systems."[5] The Anthropocene is related to the global warming and the Holocene Extinction events, which are ongoing right now. Labidura herculeana, the largest known earwig, is among the numerous species extinct after 1950.
Geography[]
During the Pleistocene, the polar regions in the northern hemisphere were covered with ice masses. The continents in the Quaternaty took their current shape, and their movement was insignificant over 2.58 million years. However, due to the advance and retreat of glaciers in the northern hemisphere, sea levels and coastlines were constantly changing. Land bridges appeared and disappeared between Chukotka and North America and between Indochina and Australia, facilitating the exchange of fauna between parts of the world. Around 780,000 years ago, the land masses that would become Easter Island began to form. About 400,000 years ago, the youngest island of the Hawaiian archipelago was formed. During periods of maximum glaciation, the North and Baltic seas completely dried out, and in their place lay plains where large herbivores grazed. In Asia, the growth of the Himalayas continued and still continues.
With the end of the last glaciation at the beginning of the Holocene, the Great Lakes of North America were formed. It is assumed that at the beginning of the Holocene the Black Sea was an isolated lake, which subsequently connected with the Mediterranean Sea through the Bosporus and Dardanelles straits. On the territory of the Sahara, before its desertification, there were gigantic fresh lakes. As a result of human activity, some inland water bodies (the Aral Sea) are drying up and new ones (reservoirs) are appearing.
Climate[]
Throughout the Pleistocene, cold temperatures persisted, alternating with short intervals of warming during interglacial periods. In place of today's coniferous northern forests, steppes inhabited by large herbivores stretched. The Holocene is characterized by new global warming, which has resulted in desertification of the Sahara and the Arabian Peninsula and continues to melt glaciers in Greenland and Antarctica, causing a worldwide rise in sea levels. The vast expanses of Eurasia and North America, as well as southern South America, New Zealand and Tasmania, maintain a seasonal climate.
Quaternary life[]
Global cooling led to the spread of cold-resistant plants and animals. Sirens and whales with a warming layer of subcutaneous fat spread across the seas. The blue whale, likely the largest animal of all time, appeared in the Pleistocene. The colder climate has likely led to a decline in shark numbers. Killer whales and sperm whales became the largest marine predators. Large sturgeon fish swam off the coasts and spawned in rivers. Before humans began hunting them in the Holocene, they, like the great sturgeon, grew to 6-9 m in length.
On land, many mammals acquired warm fur, which allowed them to populate cold low-latitude areas. The Pleistocene megafauna, including large ungulates, carnivorans and marsupial mammals, as well as large flightless birds, spread across all continents. Herds of mastodons, mammoths and bison roamed the northern steppes of Eurasia and North America; giant ground sloths, glyptodonts and camels lived in the American part of the world. All these herbivores were hunted by saber-toothed cats, lions, giant bears and canids. Giant marsupials have spread to the deserts and savannas of Australia. Huge ostriches lived in the Pleistocene steppes of Eurasia. On several islands, until the human invasion in the Holocene, giant herbivorous birds lived. Many small animals that arose in the Pleistocene still live, although their habitat has shifted much further north due to warming. In the Holocene, small and mobile species became most widespread.
The processes of speciation continue today, although humans have a strong influence on them. In Holocene, especially in the Meghalayan age, various varieties and breeds of domesticated plants and animals have appeared, which are very different from their wild relatives.
Human evolution[]
At the beginning of the Pleistocene in eastern Africa, the first human species arose from Australopithecus, Homo habilis, capable of creating and processing primitive tools. Evolving over time into several new species, humans spread from Africa to Eurasia. Before or during this settlement, such an important skill as making fire took place. Fire and primitive weapons allowed people to protect themselves from dangerous predators and make hunting easier. Homo erectus inhabited the warm regions of southern and eastern Asia. During the Pleistocene, Neanderthals hunted on the northern plains of Europe and western Asia. They endured cold winters not only due to fires and clothing made from animal wool, but also due to their large noses, which warmed the air they inhaled. Homo sapiens spread from Africa in the late Pleistocene, and this is the only human species that has gone beyond Eurasia. All human species except H. sapiens became extinct before the Holocene. The last of the other human species was probably Homo floresiensis, which became extinct on the Flores island 50,000 years ago. In the Holocene, H. sapiens created the civilization in which we live now.
Holocene Extinction[]
In the Holocene, and in some places even in the late Pleistocene, megafauna became extinct everywhere except Africa. During the Holocene, large herbivorous and carnivorous species became extinct on the territory of the first states around the Mediterranean, Black and Caspian Seas. Later, during the Age of Discovery, many species that lived on islands discovered by man were exterminated. At the end of the 20th century, the Holocene Extinction was recognized as a mass extinction. Today, this extinction continues, and every few years certain species disappear.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Cenozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=2.
- ↑ Waters, Colin N; Turner, Simon D; Zalasiewicz, Jan; Head, Martin J (April 2023). "Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series". The Anthropocene Review. 10 (1): 3–24. DOI:10.1177/20530196221136422
- ↑ "Canadian lake chosen to represent start of Anthropocene". https://www.theguardian.com/environment/2023/jul/11/nuclear-bomb-fallout-site-chosen-to-define-start-of-anthropocene.
- ↑ "The Anthropocene: IUGS-ICS Statement (2024)". https://www.iugs.org/_files/ugd/f1fc07_ebe2e2b94c35491c8efe570cd2c5a1bf.pdf.