- Key People:
- Maurice-Irénée-Marie Gignoux
Quaternary
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What is the Quaternary period?
The Quaternary Period, a unit of time in the Cenozoic Era, began approximately 2.588 million years ago and continues to the present day.
Characterized by recurring glaciations and rapid shifts in climate and sea level, it has greatly influenced environments and life forms, leading to the rise of modern humans around 200,000 years ago. It is one of the most studied geological periods due to its well-preserved, accessible rocks and sediments that hold fossils related to living organisms.
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When did the Quaternary period begin?
The Quaternary Period, a unit of time within the Cenozoic Era, began 2.588 million years ago. This period is characterized by significant climate and oceanographic changes, including the expansion of ice sheets over the northern continents. In 2009, the International Union of Geological Sciences officially ratified the decision to mark the start of the Quaternary at this time. This point also coincides with the beginning of the Gelasian Age, the lowermost stage of the Pleistocene Epoch.
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What major events happened during the Quaternary period?
The Quaternary Period, which began approximately 2.58 million years ago and continues to the present day, is marked by significant environmental and biological changes.
Major events include:
* Glaciation: Several periods of glaciation led to the formation of thick ice sheets across continents, causing rapid climate and sea level changes that altered environments worldwide.
* Evolutionary changes: These shifts drove rapid changes in flora and fauna, and are believed to have accelerated the evolution of hominins, giving rise to the genus Homo.
* Rise of modern humans: Beginning roughly 200,000 years ago, these changes contributed to the emergence of modern humans.
* Extinctions: Many large animals became extinct towards the end of the Pleistocene Epoch, possibly due to human hunting or habitat changes.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why is geochronology important for studying the Quaternary period?
Geochronology is crucial for studying the Quaternary Period because it provides the tools to determine the age and history of Earth's rocks and sediments. The Quaternary Period, which began approximately 2.58 million years ago, is characterized by significant climate changes, including multiple glaciations and the rise of modern humans.
Several dating methods, including radiometric techniques and tephrochronology, offer relatively precise timing of events and rates of change, helping to correlate deposits and establish chronologies. These methods are essential for understanding the timing and magnitude of climate shifts and their impact on environments and life-forms during this period.
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How do scientists date rocks and fossils from the Quaternary period?
Scientists employ various methods to date rocks and fossils from the Quaternary period, which spans the last 2.6 million years. These methods include:
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Radiocarbon dating: This technique measures the decay of carbon-14 in organic materials and can date samples up to roughly 60,000 years old.
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Uranium-Thorium series radioisotopes: These isotopes have short half-lives and are suitable for dating geologically young materials.
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Tephrochronology: This method identifies and correlates layers of volcanic ash (tephra) to establish a chronology. Volcanic ash horizons serve as clear markers that are simultaneous in many cores and can be correlated to radiometric dates.
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Fission-track dating: This method calculates the age of a sample based on the number of tracks present and the uranium content.
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Dendrochronology: In regions with seasonal climate contrasts, the age of a tree can be determined by counting its growth rings.
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What are some examples of geochronological methods used in studying the Quaternary?
The Quaternary Period, which began approximately 2.58 million years ago, is characterized by significant climatic and environmental changes, including multiple glaciations and the rise of modern humans. Geochronological methods are vital for establishing the timing and sequence of events during this period.
Examples of dating methods used in studying the Quaternary:
* Radiocarbon dating: This method is applied to organic materials and relies on the decay of carbon-14 to date samples up to roughly 60,000 years old.
* Potassium-argon dating: This technique measures the ratio of radioactive argon to radioactive potassium in rocks and minerals, and it can be used on volcanic rocks as young as 20,000 years old.
* Uranium-thorium series dating: This method uses the decay chains of uranium and thorium to date geologically young materials, such as corals.
* Lead-210 dating: By measuring the amount of lead-210, the age of glacial ice and sedimentary materials can be estimated.
* Thermoluminescence: This method measures the light emitted from minerals and crystalline materials when heated, which can be correlated to the time since their last exposure to radiation.5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Quaternary, in the geologic history of Earth, a unit of time within the Cenozoic Era, beginning 2,588,000 years ago and continuing to the present day. The Quaternary has been characterized by several periods of glaciation (the “ice ages” of common lore), when ice sheets many kilometres thick have covered vast areas of the continents in temperate areas. During and between these glacial periods, rapid changes in climate and sea level have occurred, and environments worldwide have been altered. These variations in turn have driven rapid changes in life-forms, both flora and fauna. Beginning some 200,000 years ago, they were responsible for the rise of modern humans.
The Quaternary is one of the best-studied parts of the geologic record. In part this is because it is well preserved in comparison with the other periods of geologic time. Less of it has been lost to erosion, and the sediments are not usually altered by rock-forming processes. Quaternary rocks and sediments, being the most recently laid geologic strata, can be found at or near the surface of the Earth in valleys and on plains, seashores, and even the seafloor. These deposits are important for unraveling geologic history because they are most easily compared to modern sedimentary deposits. The environments and geologic processes earlier in the period were similar to those of today; a large proportion of Quaternary fossils are related to living organisms; and numerous dating techniques can be used to provide relatively precise timing of events and rates of change.
The term Quaternary originated early in the 19th century when it was applied to the youngest deposits in the Paris Basin in France by French geologist Jules Desnoyers, who followed an antiquated method of referring to geologic eras as “Primary,” “Secondary,” “Tertiary,” and so on. Beginning with the work of Scottish geologist Charles Lyell in the 1830s, the Quaternary Period was divided into two epochs, the Pleistocene and the Holocene, with the Pleistocene (and therefore the Quaternary) understood to have begun some 1.8 million years ago. In 1948 a decision was made at the 18th International Geological Congress (IGC) in London that the base of the Pleistocene Series should be fixed in marine rocks exposed in the coastal areas of Calabria in southern Italy. As ratified by the International Commission on Stratigraphy (ICS) in 1985, the type section for boundary between the Pleistocene and the earlier Pliocene occurs in a sequence of 1.8-million-year-old marine strata at Vrica in Calabria. However, no decision was made to equate the beginning of the Pleistocene Epoch to the beginning of the Quaternary Period, and indeed the very status of the Quaternary as a period within the geologic time scale had come into question. Various gatherings of the IGC in the 19th and 20th centuries had agreed to retain both the Tertiary and Quaternary as useful time units, particularly for climatic- and continent-based studies, but a growing number of geologists came to favour dividing the Cenozoic Era into two other periods, the Paleogene and the Neogene. In 2005 the ICS decided to recommend keeping the Tertiary and Quaternary in the time scale, but only as informal sub-eras of the Cenozoic.
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The ICS abandoned the sub-era structure in 2008, deciding instead to formally designate the Quaternary as the uppermost period of the Cenozoic Era, following the aforementioned Paleogene and Neogene periods. In 2009 the International Union of Geological Sciences (IUGS) officially ratified the decision to set the beginning of the Quaternary at 2,588,000 years ago, a time when rock strata show extensive evidence of widespread expansion of ice sheets over the northern continents and the beginning of an era of dramatic climatic and oceanographic change. This time is coincident with the beginning of the Gelasian Age, which was officially designated by the IUGS and the ICS in 2009 as the lowermost stage of the Pleistocene Epoch. The type section for the Gelasian Stage, the rock layer laid down during the Gelasian Age, is found at Monte San Nicola near Gela, Sicily.