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The Abstract

A Billion Years Are Mysteriously Missing From Earth’s History. Now, We Know Why.

Becky Ferreira Becky Ferreira
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The Great Unconformity — a gap in Earth’s geological record — has puzzled scientists for 150 years. New research suggests it was created by shifting continents, rather than “snowball Earths” or Cambrian life.
A Billion Years Are Mysteriously Missing From Earth’s History. Now, We Know Why.
A segment of the Great Unconformity in North China, where a ~2.18 billion-year-old granitic basement is under a ~520 million-year-old Cambrian sandstone. Image: Liang Duan
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Scientists have resolved a longstanding mystery about the Great Unconformity, a huge gap in the geological record that shows up across the world and has inspired speculation for more than 150 years, reports a study published on Monday in Proceedings of the National Academy of Sciences.

The unconformity shows up around the world when sedimentary rock that is about 500 million years old lies directly on top of far more ancient “basement” rock that can be often over 1.7 billion years old. The missing layers can represent anywhere from several million to more than a billion years, making this feature “arguably the most iconic but enigmatic gap in Earth’s stratigraphic record,” according to the new study. 

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