You’ve probably seen the Redwall Limestone beforeThe Redwall Limestone might very well be the single

You’ve probably seen the Redwall Limestone beforeThe Redwall Limestone might very well be the single most distinctive unit in Grand Canyon. Passengers flying overhead in airplanes can often make out its massive, red-stained faces.The Redwall is a limestone from the Mississippian period. At this time, a great, warm, tropical seaway covered the Western portion of North America. All sorts of life lived in these seaways, forming all sorts of shells and leaving enormous piles of fossils and carbonates that wound up as hundreds of meters of limestone.The Redwall contains very little sediment that isn’t carbonate. Most of the rocks in the Canyon have a silicic component even if they are limestones; in the Redwall contains <1%. That implies that the seaway was so extensive the shoreline was just a huge distance away. There just wasn’t any sediment supplied to this area other than the life.The unit is rich in fossils and sedimentary structures, including crinoids, brachiopods, corals, bryozoans, ooids, cherts, and various types of cross-bedding.Perhaps the most noteworthy feature of the Redwall limestone is that the rock itself is not red. The color is supplied from above; reddish sediments wash down from the shales above, painting the exposed surfaces of the limestone a brilliant red.The sharp face of the Redwall occurs as a consequence of the behavior of limestone. Limestone erodes easily with water flow but doesn’t break up easily without water. Thus, in a mostly arid area like the Grand Canyon, the Redwall makes sharp cliffs that even climbers will struggle with unless the rocks are otherwise broken. But, where water does flow, spectacular waterfalls and caves can be found in this unit.-JBBImage credits:https://www.flickr.com/photos/grand_canyon_nps/7706754222https://www.flickr.com/photos/alanenglish/4599793309Sources:http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/redwall.htmhttp://www.bobspixels.com/kaibab.org/geology/gc_layer.htm#rlhttp://www.utahgeology.com/fm_redwall.phpPrevious articles:https://www.facebook.com/photo.php?fbid=71718732167564https://www.facebook.com/photo.php?fbid=717596974968016https://www.facebook.com/photo.php?fbid=718487278212319https://www.facebook.com/TheEarthStory/posts/718917208169326https://www.facebook.com/TheEarthStory/posts/719035941490786https://www.facebook.com/TheEarthStory/posts/719534524774261https://www.facebook.com/photo.php?fbid=720485404679173https://www.facebook.com/photo.php?fbid=720916891302691https://www.facebook.com/TheEarthStory/posts/721282287932818https://www.facebook.com/TheEarthStory/posts/721455997915447https://www.facebook.com/TheEarthStory/posts/722212221173158https://www.facebook.com/TheEarthStory/posts/722332104494503https://www.facebook.com/TheEarthStory/posts/723288294398884https://www.facebook.com/TheEarthStory/photos/a.352867368107647.80532.352857924775258/723925267668520/?type=1https://www.facebook.com/TheEarthStory/photos/a.352867368107647.80532.352857924775258/724756080918772/?type=1https://www.facebook.com/TheEarthStory/posts/724792024248511https://www.facebook.com/TheEarthStory/posts/725410850853295https://www.facebook.com/TheEarthStory/posts/726153457445701https://www.facebook.com/TheEarthStory/posts/726938514033862https://www.facebook.com/TheEarthStory/posts/727461423981571https://www.facebook.com/TheEarthStory/posts/727462763981437 -- source link
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