At https://phys.org/print447061881.html … it is 50 years since the last formation was discovered and defined in the Grand Canyon but now geologists have been having a look at the Sixty Mile Formation – and their research is published in Nature Geoscience. It seems this particular piece of the Grand Canyon is somewhat younger than thought – ie it was generally labelled PreCambrian. The Sauk marine transgression event is dated between 600 and 500 million years ago and the formation is somewhat older. In this event the sea flooded large tracts of North America, leaving behind tell tale zircons. It is determined as caused by subsidence along a rift margin – but that means it is open to debate. The Sixty Mile Formation has been redated to the mid to late Cambrian.
Note … this has nothing to do with the formation of the grand canyon – but pertains to the rock strata revealed in the gash in the rocks that is the canyon.