Earth's "Missing" Billion Years: Study Links the Great Unconformity to Early Tectonics

"The Great Unconformity is a widespread gap in the geologic record where more than a billion years of Earth's history appear to have been erased. This "missing chapter" occurs where sedimentary rocks from the Cambrian Period sit directly atop much older igneous and metamorphic rocks, often called crystalline basement. The gap reflects both the erosion of older rocks and long intervals when little or no sediment was deposited."

"Scientists have long debated what geologic forces may have caused so much of the rock record to vanish. To date, there have been two main theories: One proposes that during the icy Cryogenian Period, about 700 million years ago, a Snowball Earth glaciation event eroded kilometers of continental crust. The other attributes tectonic uplift from the formation and breakup of supercontinents as the main cause of erosion."

"According to recent findings published in Proceedings of the National Academy of Sciences, the latter theory prevails: Tectonic forces associated with early supercontinent formation were largely responsible for the Great Unconformity."

The Great Unconformity represents a major gap in Earth's geologic record where over a billion years of history appears missing, occurring where Cambrian sedimentary rocks sit directly atop much older crystalline basement rocks. This gap results from both erosion of older rocks and extended periods of minimal sediment deposition. Scientists debated two competing theories: Snowball Earth glaciation around 700 million years ago eroding continental crust, or tectonic uplift from supercontinent formation and breakup. Recent research analyzing basement rocks in the North China Craton supports the tectonic theory, demonstrating that tectonic forces associated with early supercontinent formation were primarily responsible for creating the Great Unconformity.

Read at State of the Planet