When one conveys certain things, particularly of such gravity, should one not then appropriately cite sources, authorities...
Started by Recusant, May 02, 2020, 08:30:19 PM
Quote from: Randy on June 10, 2020, 02:28:49 PMNah, eternity sounds boring. Besides, worshiping for eternity does not seem like paradise to me.
QuoteA new study led by the University of Colorado Boulder reveals the complex history behind one of the Grand Canyon's most well-known geologic features: A mysterious and missing gap of time in the canyon's rock record that covers hundreds of millions of years.The research comes closer to solving a puzzle, called the "Great Unconformity," that has perplexed geologists since it was first described nearly 150 years ago.Think of the red bluffs and cliffs of the Grand Canyon as Earth's history textbook, explained Barra Peak, lead author of the new study and a graduate student in geological sciences at CU Boulder. If you scale down the canyon's rock faces, you can jump back almost 2 billion years into the planet's past. But that textbook is also missing pages: In some areas, more than 1 billion years' worth of rocks have disappeared from the Grand Canyon without a trace.Geologists want to know why."The Great Unconformity is one of the first well-documented geologic features in North America," Peak said. "But until recently, we didn't have a lot of constraints on when or how it occurred."Now, she and her colleagues think they may be narrowing in on an answer in a paper published this month in the journal Geology. The team reports that a series of small yet violent faulting events may have rocked the region during the breakup of an ancient supercontinent called Rodinia. The resulting havoc likely tore up the earth around the canyon, causing rocks and sediment to wash away and into the ocean.[Continues . . .]
QuoteAbstract:The Great Unconformity is an iconic geologic feature that coincides with an enigmatic period of Earth's history that spans the assembly and breakup of the supercontinent Rodinia and the Snowball Earth glaciations. We use zircon (U-Th)/He thermochronology (ZHe) to explore the erosion history below the Great Unconformity at its classic Grand Canyon locality in Arizona, United States. ZHe dates are as old as 809 ± 25 Ma with data patterns that differ across both long (∼100 km) and short (tens of kilometers) spatial wavelengths. The spatially variable thermal histories implied by these data are best explained by Proterozoic syndepositional normal faulting that induced differences in exhumation and burial across the region. The data, geologic relationships, and thermal history models suggest Neoproterozoic rock exhumation and the presence of a basement paleo high at the present-day Lower Granite Gorge synchronous with Grand Canyon Supergroup deposition at the present-day Upper Granite Gorge. The paleo high created a topographic barrier that may have limited deposition to restricted marine or nonmarine conditions. This paleotopographic evolution reflects protracted, multiphase tectonic activity during Rodinia assembly and breakup that induced multiple events that formed unconformities over hundreds of millions of years, all with claim to the title of a "Great Unconformity."[¶ added. - R]