Mantle currents caused large gaps in Earth's geological record

Santosh Dhungana and Nicolas Flament used computer modeling to show that mantle convection currents caused the Great Unconformity, a massive gap in the geological history of Earth.

The researchers, from the University of Wollongong in Australia, published their findings in the journal Nature. The Great Unconformity occurs when sedimentary rocks from the Cambrian period, which are about 540 million years old, sit directly on top of much older crystalline rocks like granite.

This missing record appears in various locations, including the Grand Canyon in the United States and across Europe, Australia, Africa, and Asia. Depending on the specific site, the missing geological data can span from 200 million years to over a billion years. The study shows that hot rock currents in the mantle moved very slowly to lift and sink entire continents.

During the Neoproterozoic era, which lasted from 1 billion to 540 million years ago, these currents pushed up the continental cores of Laurentia, Baltica, and North China. This uplift was followed by a long period of sinking during the Phanerozoic eon, which covers the last 540 million years. As these landmasses subsided into the ocean, seas and sediment buried the worn rock surfaces to create the current geological gap.

The models created by Dhungana and Flament matched the specific locations where the Great Unconformity is most visible. The researchers found that the combination of a long period of uplift followed by a long period of sinking provided the necessary conditions to remove older rock and preserve the worn surface. This research provides a tested explanation for why these specific sections of Earth's history appear to be missing.