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About 34 million years ago, Earth began to cool dramatically, transforming the climate from greenhouse to icehouse and causing sea levels to fall. As more land was exposed to weathering forces, copious amounts of sediment likely sloughed off continents into the oceans, bound for the deep seafloor.

So, when Montana State University assistant professor Zachary Burton, then a doctoral student at Stanford University, set out to see how that sediment had accumulated as submarine layers of sand and mud, he expected there would be much to discover.

To his surprise, he instead found—nothing.

The journal Earth-Science Reviews has published Burton's findings, which reveal the existence of a global unconformity—or gap in the rock record—around the edges of every continent at the time of the pivotal greenhouse-to-icehouse climatic transition.

In addition to challenging conceptual models widely used for the past half-century about the relationships between sea levels and sediment movement in the deep oceans, Burton said his discovery has left him and his co-authors wondering: Where in the world did all the sediment go?

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