Preboreal Stage: The Dawn of the Holocene Epoch
The Preboreal represents a pivotal transition in Earth's geological history, marking the very beginning of the Holocene epoch. Following the end of the Pleistocene, this period witnessed the initial recovery of global forests and a shift toward the climatic conditions that define our current era.
While originally defined as an informal stage, the Preboreal provides essential insights into how the planet transitioned from the last glacial period into a warmer, more stable environment. It serves as the foundational chapter of the Holocene, setting the stage for subsequent climatic shifts and biological expansions.
Key Facts
- Timeline: Lasted from 10,300 to 9,000 BP (radiocarbon years), corresponding to 8350 BC to 7050 BC.
- Position: The first stage of the Holocene epoch, preceded by the Tarantian and succeeded by the Boreal.
- Climate Event: Featured the Preboreal oscillation, a brief cooling episode lasting approximately 150 years.
- Modern Classification: Largely overlaps with the Greenlandian, the globally recognized first age of the Holocene ratified in 2018.
Stratigraphic Classification and Evolution
The term Preboreal was established as an informal subdivision of the Holocene. However, as the science of stratigraphy—the study of rock layers and layering—and dating techniques have advanced since the original 1972 proposal, the precise dating of this period has evolved.
In contemporary geological discussions, some researchers prefer using the terms Early, Middle, and Late (or Lower, Middle, and Upper) to describe Holocene sediments. Under this revised terminology, the Preboreal would be categorized as the Lower Holocene, spanning from 11.7 to 8.2 ka B2K (thousands of years before the year 2000).
To standardize these definitions globally, the International Commission on Stratigraphy (ICS), a branch of the International Union of Geological Sciences (IUGS), ratified the Greenlandian in July 2018. The Greenlandian is now the official globally recognized first age of the Holocene, encompassing much of the timeframe previously described by the regional North European term "Preboreal."
Comparing Holocene Chronologies
The timeline of the Holocene can be viewed through different lenses: the official ICS stages and the regional Blytt–Sernander stages. The latter provides a more granular look at the climatic shifts experienced in North Europe.
| ICS Official Ages | Blytt–Sernander Stages | Approximate Timeframe |
|---|---|---|
| Greenlandian | Preboreal | 11.7* – 8.236* ka / 10.3†–9† ka |
| Greenlandian / Northgrippian | Boreal | 9 – 7.5† ka |
| Northgrippian | Atlantic | 7.5 – 5† ka |
| Northgrippian / Meghalayan | Subboreal | 5 – 2.5† ka |
| Meghalayan | Subatlantic | 2.5 ka – Present |
* Relative to year 2000 (b2k). † Indicates estimated dates.
Frequently Asked Questions
What exactly is the Preboreal?
The Preboreal is an informal stage marking the beginning of the Holocene epoch. It is characterized by the recovery of forests following the Pleistocene epoch.
When did the Preboreal occur?
In radiocarbon years, it lasted from 10,300 to 9,000 BP. In the Gregorian calendar, this corresponds to the 8th millennium BC, specifically from 8350 BC to 7050 BC.
What was the Preboreal oscillation?
The Preboreal oscillation was a short-lived cooling episode that occurred within the Preboreal stage, lasting roughly 150 years.
How does the Preboreal differ from the Greenlandian?
The Preboreal is a regional North European term, whereas the Greenlandian is the official, globally recognized first age of the Holocene ratified by the International Commission on Stratigraphy in 2018.
What comes after the Preboreal?
The Preboreal is succeeded by the Boreal stage in the Blytt–Sernander chronology.