|Subdivisions of the Quaternary System|
|Subdivision of the Quaternary period|
according to the ICS, as of 2017.
In Europe and North America, the Holocene is subdivided into Preboreal, Boreal, Atlantic, Subboreal, and Subatlantic stages of the Blytt–Sernander time scale. There are many regional subdivisions for the Upper or Late Pleistocene; usually these represent locally recognized cold (glacial) and warm (interglacial) periods. The last glacial period ends with the cold Younger Dryas substage.
A great majority of extinctions in Afro-Eurasia and the Americas occurred during the transition from the Pleistocene to the Holocene epoch (13,000 BCE to 8,000 BCE). Abrupt climate change has been associated with the last glacial period, possibly due to the Younger Dryas event, in combination with Tollmann's hypothetical bolide.
Alexander Tollmann proposed that extinctions occurred from bolide impacts. Impact scenarios have been proposed as the contributing cause of the 1,300-year cold period known as the Younger Dryas stadial. Impact extinction hypothesis is still an active debate due to the exacting field techniques required to extract minuscule particles of extraterrestrial impact markers. An example of the difficulty is tracing iridium, which requires a high resolution potentially available only from a very thin strata and needed in a repeatable fashion, to conclusively distinguish the event peak from the local background level of any impact markers.
- ↑ http://www.stratigraphy.org/index.php/ics-chart-timescale
- ↑ "Holocene". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/Holocene.
- ↑ "Holocene". Wikipedia:Dictionary.com Unabridged. Random House. http://www.dictionary.com/browse/Holocene.
- ↑ International Commission on Stratigraphy. "International Chronostratigraphic Chart" (in en-gb). http://www.stratigraphy.org/index.php/ics-chart-timescale.