The story
About 579 million years ago the Earth cooled again and glaciers spread across parts of the globe. The event is named for the Gaskiers Formation on the Avalon Peninsula of Newfoundland, Canada, where thick layers of glacial debris called diamictite lie between volcanic rocks. Matching deposits are known from Britain, Scandinavia, China and elsewhere. Uranium-lead dating of volcanic ash beds, notably by Pu and colleagues in 2016, shows the glaciation was short, lasting well under a few million years.
It came after the two older Cryogenian glaciations of Snowball Earth, which were far longer and probably covered the sea in ice. Gaskiers was probably smaller, and how far its ice reached toward the equator is still debated. Its importance is timing: the oldest large, complex fossils in the world appear in Newfoundland rocks less than ten million years afterward, at Mistaken Point. Some researchers suggest that cooling and mixing of the oceans, followed by melting and a rise in oxygen and nutrients, set the stage for the first big soft-bodied life, but the link is a hypothesis rather than a proven chain.
Why it mattered
- Gaskiers marks the last glacial episode before the Ediacaran biota, the first large complex life, spreads across the seafloor.
- Its short length and uncertain extent help scientists judge how extreme Earth's climate swings were before the Cambrian.
- The Newfoundland sections give a precise dated reference point for correlating Ediacaran rocks worldwide.
Sources
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