Science & Tech · Science & Environment · 3 hrs ago
Swedish sediment separates events linked to the Younger Dryas cooling
A sediment core from a Swedish fen adds evidence to debate over the Younger Dryas, a sudden Northern Hemisphere cold period that began about 12,800 years ago.
The core contains ash from Germany’s Laacher See volcano, dated to about 13,006 years ago.
A separate layer of unusual particles appeared roughly 150 years later, just before the sediment showed the shift to colder, wetter conditions.
The particles include iron-silicon microspherules and high levels of several elements, with some chemical signatures consistent with material from space.
Researchers say the findings fit a possible cosmic impact or airburst, but they do not prove one occurred.
The Younger Dryas Impact Hypothesis proposes that such an event disrupted ice sheets and Atlantic circulation, helping trigger the cooling.
The new evidence separates the volcano, particle layer and cooling into distinct events, while leaving the cause of the cold period unresolved.
A sediment core from a fen in southern Sweden indicates that the Laacher See eruption, a distinct boundary layer and the start of Younger Dryas cooling were separate events.
The Younger Dryas began around 12,800 years ago, when temperatures in the Northern Hemisphere abruptly returned toward near-glacial conditions.
Researchers found a layer containing microspherules and elevated levels of platinum-group elements above ash from the Laacher See eruption.
The layer’s chemistry is consistent with extraterrestrial material, but the researchers stop short of claiming a cosmic impact or airburst caused it.
The findings add evidence to a long-running debate about what triggered the cooling.
- Who
- A research team led by Christopher Moore, a research professor at the University of South Carolina, with collaborators including Stockholm University and the University of California Santa Barbara.
- What
- Researchers analyzed a sediment core that separates the Laacher See eruption, a boundary layer and the onset of Younger Dryas cooling.
- When
- The Younger Dryas began around 12,800 years ago. The study’s publication date is not stated.
- Where
- The Körslättamossen fen in northwest Scania, southern Sweden.
- Why
- The research provides evidence about the timing and relationship of events linked to Younger Dryas cooling; its trigger remains debated.
Proponents of the Younger Dryas Impact Hypothesis
Critics of the hypothesis
Interpretation of the evidence
Proponents of the Younger Dryas Impact Hypothesis
Proponents argue that a cosmic impact or series of airbursts destabilized the Laurentide Ice Sheet, disrupted Atlantic circulation and triggered the cooling.
Critics of the hypothesis
Critics have questioned whether reported signals, including platinum enrichments and microspherule layers, can be replicated.
The Laacher See volcano in Germany erupted.
Ash from the eruption was found at 288.5 centimeters depth in the Swedish sediment core.
The distinct layer enriched with microspherules and platinum-group elements was dated to this time.
Sediment records a sudden shift to colder and wetter conditions marking the onset of Younger Dryas cooling.
- Core site
- Körslättamossen fen, northwest Scania, southern Sweden
- Ash depth
- 288.5 centimeters
- Laacher See ash age
- 13,006 ± 9 calibrated years BP
- Boundary-layer age
- 12,861 ± 54 calibrated years BP
- Boundary-layer thickness
- 3 centimeters
- Element concentrations
- Five to ten times higher than in surrounding sediments
What people are saying
This demonstrates that the volcanic eruption and the Younger Dryas Boundary were separate events
At our site in southern Sweden, we identified this boundary layer through tiny, melted particles called microspherules and unusually high concentrations of platinum-group elements.
This layer is followed almost immediately by evidence for a sudden shift to colder and wetter conditions.
This is important because it helps separate three events that have often been discussed together: the Laacher See eruption, deposition of the Younger Dryas Boundary layer and the beginning of Younger Dryas cooling.