Scientists have argued for tectonic activity or, alternatively, glaciation to explain the Great Unconformity. A Dartmouth research team favors glaciation:
This giant lapse in Earth’s memory exceeds one billion years in some places, resulting in 550 million-year-old rocks sitting atop ancient layers that date back 1.7 billion years, with no trace of the many lost epochs in between…
Now, a team led by Kalin McDannell, a postdoctoral researcher in earth sciences at Dartmouth College, has presented new evidence that glaciers were the main force that carved out this mysterious gap in time.
The researchers discovered a strong “cooling signal” at four very different geological locations across North America, suggesting that continental-scale glaciation may be “the only foreseeable process that can account for both the formation and preservation of the Great Unconformity,” according to a study published Tuesday in The Proceedings of the National Academy of Sciences.Becky Feirrera, “A Billion Years of Time Are Mysteriously Missing. Scientists Think They Know Why.” at VICE
Of course, the gap ended roughly at the same time that identifiable complex life began, roughly 550 million years ago. What was going on in the meantime is anyone’s guess.
The paper is open access.