Friday, July 29, 2011

WOGE #302

After almost winning WOGE #300, I was motivated to spend way too much time trying to locate the interesting rock formations in WOGE #301.  I usually narrow my search area by looking to see what part of the world someone's previous WOGE posts were in, but Péter Luffi has won so many times that it was no help.  I just kept looking in every southern hemisphere desert I could think of, until I finally found the spot in arid western Argentina.
Below is WOGE #302.  Please note that I have used an "historic image" from Google Earth not just to make things more difficult, but because this image shows the features of geologic interest a little more clearly than the current one.
  Once you find this location, information on the geology (and lots of great pictures) will be easy to find.  I will not invoke the "Schott rule" this time.  In case anyone doesn't know what WOGE is, you can find a brief explanation (and a link for more details) in my previous post.  Have fun everyone!

Now that this edition of WOGE has been solved, I will provide some color.  Felix Bossert shares an excellent description of the geology in his comment.


  1. 32.066231°, -84.905118° Providence Canyon, Georgia, US

    Providence Canyon is a network of gorges in southwest Georgia created by the erosion of soft, multicolored soils. Erosion has exposed the geologic record of several million years within its walls, and minerals have stained the sediments, creating a display of colors that range from white to various shades of pink, purple, red, brown, yellow, and black.

    Providence Canyon is not a purely natural feature, the massive gullies (the deepest being 150 feet) were caused by erosion due to poor farming in the 19th century. Historical accounts indicate that the canyon began forming in the early 1800s. Native forest cover had been cleared so the land could be farmed, and early-nineteenth-century farmers in this region took no measures to avoid soil erosion. Small gullies formed and rapidly grew deeper and more extensive.

    The canyon has been carved from unconsolidated sediments deposited by water in ancient streams, seas, deltas, and coastal beaches between 59 and 74 million years ago.
    The sediments forming the canyon are being separated into four major geologic formations: Baker Hill, Clayton, Providence, and Ripley.

    The Baker Hill formation is the youngest and forms the uppermost part of soils. Deposited about 59 to 62 million years ago during the Paleogene period, this formation does not appear in the canyon walls, but the entrance road to the state park lie on top of it.

    The Clayton formation, visible in the top part of the canyon walls, also was deposited during the Paleogene period, about 63 to 65 million years ago. Its fairly coarse sand is a reddish color, caused by the presence of iron oxide. Near the base of this formation, iron oxides have precipitated into a thin, dark layer of iron ore.

    The Providence formation makes up most of the canyon walls. One hundred and nineteen feet thick, it was deposited during the Cretaceous period, about 67 to 70 million years ago. The upper layer of this formation consists of very fine sand mixed with a white clay called kaolin.
    The middle layer is coarser-grained and more colorful, with crossbeds stained yellow by limonite and purple by manganese.
    The lowest and oldest layer is a black and yellow mica-rich clay. This part of the formation is known as the Perote member and is visible near the bottom of the canyon.

    The Ripley formation forms the canyon floor. Deposited during the Cretaceous period, about 70 to 74 million years ago, it is orange in color, and its composition varies from clay to a massively bedded sand.

  2. Puuh, hard to find. The lack of natural colors makes it very hard to find it, as one doesn't know if one particular shade of grey is sand or gras or rock or whatever. Also the small scale was nor really helpful. On the other hand we got a obvious copyright information, so it was clear we had to look in the US. The major trick was the historical date of 2.5.1999. So I was checking pictures of 100x100km, if this date stamp was included. I started in the west and found out, that pictures of 2.5.1999 are only in the area of Alabama/Georgia/Tennessee. After scanning over these states, I got it.

  3. Congratulations to Felix Bossert for finding WOGE #302. I was worried that the small scale and black and white photo might make Providence Canyon too difficult to find, but the "canyons" really show up well in this view. Thanks for sharing the method you used to narrow your search. I would not have thought of doing that. I look forward to seeing what you have in store for #303. I have also added a few of my own photos to compensate for the lack of color in the original image. The group of canyons that the road curves around on the left side is preserved as a state park.