Burdigalian Age: The First Great Warming of the Miocene
The Burdigalian is a critical interval in Earth's history, representing a formal age and stage within the early Miocene epoch. Spanning from 20.45 to 15.98 million years ago (Ma), it serves as a bridge between the Aquitanian and the Langhian stages. Notably, the Burdigalian stands out as the first and longest warming period of the Miocene, marking a significant shift in the planet's climatic and biological trajectory.
[ไม่มีภาพประกอบ]
Key Facts
- Time Span: 20.45 Ma to 15.98 Ma.
- Epoch: Early Miocene (part of the Neogene period).
- Etymology: Named after Burdigala, the Latin name for Bordeaux, France.
- Climate: The longest warming period of the Miocene.
- Key Biological Marker: First appearance of the foraminiferan Praeorbulina glomerosa at its upper boundary.
Stratigraphic Definition
The Burdigalian Stage was first introduced to scientific literature by Charles Depéret in 1892. In geology, a stage refers to a stratigraphic unit of rock, while an age refers to the specific time interval it represents.
Defining the Boundaries
The boundaries of the Burdigalian are identified through a combination of biostratigraphy (the study of fossils) and magnetostratigraphy (the study of magnetic polarity in rocks).
- Lower Boundary: While not yet formally defined by a Global Boundary Stratotype Section and Point (GSSP), the base is associated with the first appearance of the planktonic foraminiferan (microscopic single-celled organisms) Globigerinoides altiaperturus and the top of magnetic polarity chronozone C6An.
- Upper Boundary: The transition to the Langhian stage is marked by the first appearance of the foraminiferan Praeorbulina glomerosa, which coincides with the top of magnetic chronozone C5Cn.1n. Candidate sections for this boundary include La Vedova in Italy and St. Peter's Pool in Malta.
Paleontology and Evolutionary Milestones
The Burdigalian is renowned for several high-profile paleontological sites that provide a window into ancient ecosystems. Notable examples include the Turritellenplatte of Ermingen in Germany and the famous Dominican amber deposits found in Hispaniola, which preserve an extraordinary array of prehistoric life.
From an evolutionary perspective, this era was pivotal for primate development. Victoriapithecus, a possible ancestor to later human evolutionary lineages, evolved during this time interval.
Paleoclimatology and Environmental Change
The Burdigalian was characterized by a general warming trend, but it also saw the beginnings of significant regional environmental shifts. Toward the end of the period, approximately 17 to 16 million years ago, southwestern Africa began to undergo desertification, the process by which fertile land becomes desert.
| Feature | Details |
|---|---|
| Time Range | 20.45 – 15.98 Ma |
| Preceding Stage | Aquitanian |
| Succeeding Stage | Langhian |
| Primary Climate Trend | Longest Miocene warming period |
| Key Fossil Markers | G. altiaperturus (base), P. glomerosa (top) |
| Notable Fauna | Victoriapithecus |
Frequently Asked Questions
What does the name Burdigalian mean?
The name is derived from Burdigala, which is the Latin name for the city of Bordeaux in France.
When did the Burdigalian age occur?
It occurred during the early Miocene, specifically between 20.45 and 15.98 million years ago.
What is the significance of the Burdigalian in terms of climate?
It is recognized as the first and longest warming period of the Miocene epoch.
Which fossils are used to define the Burdigalian boundaries?
The lower boundary is associated with Globigerinoides altiaperturus, and the upper boundary is defined by the first appearance of Praeorbulina glomerosa.
What major environmental change happened in Africa during this time?
Southwestern Africa began to desertify near the end of the Burdigalian, roughly between 17 and 16 million years ago.