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GLACIAL EROSION THEORY. “Erosion alone can't explain all the details of this episode, and you need something that affects the entire globe. Is there anything else that can wipe a few kilometers of rock off the Earth's face? The authors propose that three periods of epic cold snaps in the 180 million years leading up to the start of the Cambrian—sometimes referred to as “Snowball Earth” periods—could be the key.” https://lnkd.in/d3DMx6k View in LinkedIn

TECHNOLOGY. "It is vastly easier to theorize about technology than it is to measure it. It is our principal contention that patent technology codes can be used to track and characterize technological change." https://lnkd.in/dp-phxx View in LinkedIn

ZIRCONIUM DATA. “The zircons in the database span nearly the entire history of the Earth, and by far the most noticeable wiggle lines up neatly with the Great Unconformity. When they ran the numbers to see how much erosion would be required to explain a wiggle of that size, they found that it would be something in the neighborhood of 3 kilometers (or 2 miles) of rock shaved off all the world’s continents and dumped on the ocean floor.” https://lnkd.in/dtYSB5v View in LinkedIn

GLOBAL GAP. “This gap can be found all around the world, and has picked up the name the Great Unconformity. Cambrian sedimentary rocks rarely rest on anything other than much older metamorphic or igneous rock, implying that whatever rock formed in the intervening time was scrubbed away by something. This erasure of a chunk of geologic history has long been an enticing mystery for geologists.” https://lnkd.in/dtYSB5v View in LinkedIn

ONE FIFTH OF HISTORY RIPPED OUT. “Believe it or not, the geology at the bottom of the Grand Canyon is extraordinarily common. There, layers of sedimentary rock lie flat atop angled layers of significantly more ancient metamorphic rock. The gap there is enormous—if Earth’s rocks constitute a book of the planet’s history, there are about a billion pages missing. The story only picks up again around 540 million years ago in the Cambrian period, with an evolutionary explosion of complex life just as remarkable as the sudden change in the rock.” https://lnkd.in/dtYSB5v View in LinkedIn

GRAND CANYON UNCONFORMITY. “Within the Grand Canyon, the Great Unconformity represents a period of about 175 million years between the Tonto Group and the youngest subdivision, the Sixtymile Formation, of the Grand Canyon Supergroup. At the base of the Grand Canyon Supergroup, where it truncates the Bass Formation, the period of time represented by this angular unconformity increases to about 725 million years. Where the Tonto Group overlies the Vishnu Basement Rocks, the Great Unconformity represents a period as much as 1.2 to 1.6 billion years of time.” https://lnkd.in/ddDSSXe View in LinkedIn

CYCLIC TECTONICS. “The "great" unconformities of regional or continental scale (in both geography and chronology) are associated with either global changes in eustatic sea level or the supercontinent cycle, the periodic merger of all the continents into one approximately every 500 million years.” https://lnkd.in/ddDSSXe View in LinkedIn

CALCIFICATION CAMP. “That puts the relationship between the Great Unconformity and the Cambrian explosion in a much different light. The Great Unconformity may not simply be a gap in the record of early evolution of multicellular life with fossilizable hard parts. Instead, the seawater changes caused by the erosion that created the Great Unconformity may have driven the rise of biological calcification.” https://lnkd.in/dtYSB5v View in LinkedIn

ISOTOPE SUPPORT. “Support for this idea can also be found in the ratio of strontium isotopes. Strontium-87 mainly makes it into the ocean through the breakdown of continental rocks, whereas strontium-86 comes from mid-ocean ridges. The high point for strontium-87 over the past 900 million years occurred during the Cambrian, suggesting weathering peaked around then. The ratio of neodymium-143 to neodymium-144 (also known as εNd) also helps out by indicating the age of those continental rocks being weathered. Around the time that strontium-87 peaked, εNd hit a low point as continental weathering cut into older and older rocks.’ https://lnkd.in/dtYSB5v View in LinkedIn

MELTING GLACIERS. “When sea level rose (and the first Cambrian sediments were laid down on the continents) it swabbed the decks. Nothing erodes quite like the power of waves, so as the shoreline gradually moved inland to higher elevations it washed away the soil and sediment that had built up while rocks broke down. This "wave-base razor," as it’s called, cleared out the material that might have otherwise formed sedimentary rocks, and exposed massive areas of "fresh" bedrock. Between the weathering of these fresh surfaces (which weather very rapidly) and the continued breakdown of all the soil and sediment added to the oceans, concentrations of many ions in the seawater rose quickly.” https://lnkd.in/dtYSB5v View in LinkedIn