#tapeats

[lizardtracks]

Grand Canyon: Mile 135

9/16/17: No, you did not see that date wrong. My mind is on Grand Canyon today. My trip of a lifetime through Grand Canyon on the Colorado River was five years ago. The entire trip was sublime. Every mile brought something new. But... the Inner Gorge is where it became magical. This photo was taken between Tapeats and Deer Creek, on Day 13, say around Mile 135. I thought it captured the wonder and serendipity of our adventure.

[earthstory]

South Kaibab Trail

[earthstory]

The Tapeats Sandstone Throughout the Grand Canyon area, the Great Unconformity represents at least 200 million years of time where no rocks were deposited. The seas retreated, leaving the basement rocks to erode away. But, 525 million years ago, the seas returned and the geologic record resumed. The Tapeats Sandstone is the first unit on top of the Great Unconformity. The unit represents a shallow marine deposit, made up of sediments deposited in settings like modern-day sand bars, beaches, and channels.  The unit’s maximum thickness is about 250 meters, but he Tapeats actually isn’t deposited everywhere. In some places, the next unit up is actually deposited directly on top of the Grand Canyon Supergroup rocks. That means at the time of Tapeats deposition, there was substantial topography in the area. There were mesas and hills made up of the strong quartzites of the Supergroup and of the Vishnu Schist basement standing as islands amongst the channels where the sandstone was deposited. The Tapeats also, as you see here being pointed at by this helpful person from Flickr, contains a variety of larger pebble and cobble-sized clasts. Many of these are made of familiar rocks; components of the Vishnu Schist and the Shunimo Quartzite, strong units deposited previously, are reworked into the Tapeats. The presence of these large clasts also suggests high-energy flows, like debris flows or turbidites, carried the clasts out to sea. The Tapeats contains a variety of Cambrian-era fossils and trace fossils, including tracks of creatures like trilobites. It also contains the mineral glauconite, an iron-bearing mineral that forms sand-sized grains and also is likely a remnant of life, either of waste or of bodies after death. Various other sedimentary structures, like cross bedding and ripple marks are found as well. As a strong, hard to erode sandstone, the Tapeats stands out and forms the strong platform around the central gorge in many areas of the Canyon. The Tapeats also marks the beginning of a long period of marine deposition both here and throughout the Western U.S. Although the rock types change slightly, sandstones correlative to the Tapeats can be found throughout the West, again as far north as Montana, all indicating the seas rising and beginning to claim the continent. -JBB Image credits (Creative Commons): https://www.flickr.com/photos/alanenglish/3609981986 https://www.flickr.com/photos/ceedave/4647884862 References: http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/tapeats.htm http://geology.swau.edu/faculty/tapeats.html http://hikearizona.com/dexcoder.php?PID=1942 Oh you have got to visit the Tapeats on Google Streetview. https://www.google.com/maps/views/view/streetview/colorado-river/tapeats-sandstone/jXK-DOmUBE4PPqCz6A7CBw?gl=u&heading=263&pitch=107&fovy=75 Previous articles: https://www.facebook.com/photo.php?fbid=71718732167564 https://www.facebook.com/photo.php?fbid=717596974968016 https://www.facebook.com/photo.php?fbid=718487278212319 https://www.facebook.com/TheEarthStory/posts/718917208169326 https://www.facebook.com/TheEarthStory/posts/719035941490786 https://www.facebook.com/TheEarthStory/posts/719534524774261 https://www.facebook.com/photo.php?fbid=720485404679173 https://www.facebook.com/photo.php?fbid=720916891302691 https://www.facebook.com/TheEarthStory/posts/721282287932818 https://www.facebook.com/TheEarthStory/posts/721455997915447 https://www.facebook.com/TheEarthStory/posts/722212221173158 https://www.facebook.com/TheEarthStory/posts/722332104494503 https://www.facebook.com/TheEarthStory/posts/723288294398884 https://www.facebook.com/TheEarthStory/photos/a.352867368107647.80532.352857924775258/723925267668520/?type=1 https://www.facebook.com/TheEarthStory/photos/a.352867368107647.80532.352857924775258/724756080918772/?type=1 https://www.facebook.com/TheEarthStory/posts/724792024248511 https://www.facebook.com/TheEarthStory/posts/725410850853295

[oix]

. by Scott McFadyen on Flickr.

[oix]

. by Scott McFadyen on Flickr.