Standing atop the Kaibab Plateau Gotta say, no idea how I made it this far. Writing and scheduling all these has almost seemed like climbing the canyon itself. In fact, I think you can climb the Canyon in less time than it’s taken to write all these, or at least make very good progress on it. We’re officially at the top of the Grand Canyon. The Kaibab Limestone forms a great plateau that surrounds the gorge of the Colorado River, spreading out for many kilometers in either direction. Kaibab is actually a word from the local Native American tribes translating as “Mountain lying down”, a fitting summation of this unit. The Kaibab limestone was deposited in the middle-Permian. It is a true marine limestone, loaded with fossils, some of which you see here marked by the helpful folks at the Park service. The Kaibab was deposited after a marine transgression; the seas came in, covering the area that would one day be the Canyon again and creating a warm, tropical seaway where ocean critters could thrive. Those organisms lived their lives, died, and left their shells behind to build the limestone. The Kaibab predates the greatest extinction known in the geologic record at the end of the Permian. 10 million years or so after this limestone was deposited, the seas had receded again and the great dying took place. There is no record of the end-Permian recorded in the Grand Canyon, but it gives an amazing look through the Paleozoic, as we’ve seen for the last week+. As we’ve seen with previous limestones, it is difficult to erode them in dry, arid climates. The Kaibab therefore forms fairly steep, rocky cliffs at the edge of the Canyon, and most easily is removed by collapse when the shale units beneath it are eroded away. The top of the Kaibab is an unconformity, both now and in the past. Right now, the Kaibab forms a fairly flat plateau on which visitors drive to reach the Canyon and occasionally dart out for ice cream after a long day of being rained on while trying to hike around the rim. The top of the Kaibab is eroding right now, even if slowly. In the past, there was erosion on top of the Kaibab as well. The next unit up does not outcrop in Grand Canyon national park. The Moenkopi formation is a Triassic-aged shale that sits unconformably on the Kaibab, just as shales sat upon the Redwall limestone unconformably well beneath our feet. As we’ve seen with many other shales in the park, they erode easily and so the Moenkopi has been stripped away from this location, leaving the Kaibab standing as a sentinel. Looking back through time, it was penetrating the Kaibab formation that helped the rivers that we now call the Colorado to form the Grand Canyon. This is a tough unit to erode. Once streams got through it in a few locations, it often became easier to cut downwards than it was to migrate from side to side. To some extent, that is why the Canyon is there; the Kaibab and the other resistant units at the top locked the river in place, and the waters obliged by cutting downward. The Kaibab is the youngest rock in sequence in the Grand Canyon but it is not the youngest rock in the Canyon. Will I be able to cover others? Honestly, that’s up to Comcast to decide, we’ll see if they get my internet service hooked up before I run out of time to make the next post. -JBB Image credits: https://flickr/photos/jsjgeology/8411890361 https://flickr/photos/grand_canyon_nps/7706174560 https://flickr/photos/grand_canyon_nps/7706171986 Sources: bobspixels/kaibab.org/geology/gc_layer.htm 3dparks.wr.usgs.gov/coloradoplateau/lexicon/kaibab.htm sed.utah.edu/Kaibab.htm grandcanyonnaturalhistory/pages_nature/geology/1-kaibab.html Previous articles: https://facebook/photo.php?fbid=71718732167564 https://facebook/photo.php?fbid=717596974968016 https://facebook/photo.php?fbid=718487278212319 https://facebook/TheEarthStory/posts/718917208169326 https://facebook/TheEarthStory/posts/719035941490786 https://facebook/TheEarthStory/posts/719534524774261 https://facebook/photo.php?fbid=720485404679173 https://facebook/photo.php?fbid=720916891302691 https://facebook/TheEarthStory/posts/721282287932818 https://facebook/TheEarthStory/posts/721455997915447 https://facebook/TheEarthStory/posts/722212221173158 https://facebook/TheEarthStory/posts/722332104494503 https://facebook/TheEarthStory/posts/723288294398884 https://facebook/TheEarthStory/photos/a.352867368107647.80532.352857924775258/723925267668520/?type=1 https://facebook/TheEarthStory/photos/a.352867368107647.80532.352857924775258/724756080918772/?type=1 https://facebook/TheEarthStory/posts/724792024248511 https://facebook/TheEarthStory/posts/725410850853295 https://facebook/TheEarthStory/posts/726153457445701 https://facebook/TheEarthStory/posts/726938514033862 https://facebook/TheEarthStory/posts/727461423981571 https://facebook/TheEarthStory/posts/727462763981437 https://facebook/TheEarthStory/posts/727463347314712 https://facebook/TheEarthStory/photos/p.727464010647979/727464010647979/?type=1 https://facebook/TheEarthStory/posts/727464800647900 https://facebook/TheEarthStory/posts/727465573981156 https://facebook/TheEarthStory/posts/727465993981114 https://facebook/TheEarthStory/posts/727466543981059 Dear Readers, Most of our posts are not reaching you in your news feed due to fbs filtering system. 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Posted on: Thu, 07 Aug 2014 21:25:01 +0000