Priabonian: The Final Stage of the Eocene Epoch
In the vast timeline of Earth's history, the Priabonian represents a critical transitional period. As the final stage of the Eocene Epoch, it serves as the closing chapter of a warm greenhouse world before the Earth transitioned into the cooler conditions of the Oligocene. Spanning from approximately 37.71 to 33.9 million years ago (Ma), this stage is a vital component of the Paleogene Period.
To understand the Priabonian, one must look at its place within the larger Cenozoic Era. It follows the Bartonian stage and is succeeded by the Rupelian, which marks the beginning of the Oligocene Series. This period is characterized by significant biological shifts and complex stratigraphic markers used by scientists to map the history of our planet.
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Key Facts
- Time Span: 37.71 to 33.9 million years ago.
- Geologic Context: The latest age/upper stage of the Eocene Epoch.
- Succession: Preceded by the Bartonian and followed by the Rupelian.
- Etymology: Named after the hamlet of Priabona in the Veneto region of Italy.
- Primary Markers: Defined by the appearance of Chiasmolithus oamaruensis and the extinction of Hantkenina.
History and Etymology
The term "Priabonian" was first introduced to scientific literature in 1893 by researchers Ernest Munier-Chalmas and Albert de Lapparent. The name is derived from Priabona, a small hamlet located in the community of Monte di Malo within the Veneto region of northern Italy.
Interestingly, the name has also been applied to Priabona, an extinct type of fly (a dipteran in the family Pipunculidae), which was named after the specific age of the deposits in which it was discovered.
Stratigraphic Definition and Boundaries
In stratigraphy—the branch of geology concerned with the order and relative position of strata and their relationship to the geological timescale—the Priabonian is defined by specific biological milestones known as Global Boundary Stratotype Sections and Points (GSSPs).
The Lower Boundary
The base of the Priabonian is marked by the first appearance of the calcareous nannoplankton species Chiasmolithus oamaruensis. This biological marker forms the base of the nanoplankton biozone NP18. In February 2020, an official GSSP for this lower boundary was ratified at the Alano section in the Piave river, located in the Venetian Prealps of Belluno, Italy.
The Upper Boundary
The top of the Priabonian stage, which also marks the beginning of the Oligocene, is defined by the extinction of the planktonic foraminifera genera Hantkenina and Cribrohantkenina. The GSSP for this upper boundary was ratified in 1992 at the Massignano quarry section in Ancona, Italy.
Global Correlations and Regional Scales
Because local rock layers do not always align perfectly with the International Commission on Stratigraphy (ICS) timescale, geologists often use regional scales to describe the same time periods. The Priabonian overlaps with several different regional stages depending on the location:
- Australia: Overlaps the upper Johannian and lower Aldingan stages.
- California: Overlaps the upper Nanzian and lower Refugian stages.
- Southeastern US: Corresponds to the Jacksonian stage.
- New Zealand: Corresponds to the Runangan stage.
In the field of biostratigraphy (using fossils to date rock layers), the Priabonian is also coeval with various Land Mammal Ages across the globe, including the Chadronian in North America and the Headonian in Europe.
Summary of Priabonian Chronology
| Feature | Details |
|---|---|
| Epoch | Eocene |
| Preceding Stage | Bartonian |
| Succeeding Stage | Rupelian (Oligocene) |
| Lower Boundary Marker | Chiasmolithus oamaruensis |
| Upper Boundary Marker | Extinction of Hantkenina |
Frequently Asked Questions
What is the Priabonian stage?
The Priabonian is the final geological stage of the Eocene Epoch, occurring between 37.71 and 33.9 million years ago.
Where is the official boundary for the Priabonian located?
The lower boundary (base) is located at the Alano section in Belluno, Italy, while the upper boundary (top) is located at the Massignano quarry section in Ancona, Italy.
How is the Priabonian named?
It is named after the Italian hamlet of Priabona, located in the Veneto region.
What biological events define the start and end of this stage?
The stage begins with the appearance of the nannoplankton Chiasmolithus oamaruensis and ends with the extinction of the planktonic foraminifera Hantkenina.
Does the Priabonian exist in all geological scales?
While the ICS timescale is the global standard, different regions like Australia, California, and New Zealand use their own regional stages that overlap with the Priabonian.