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You are browsing the archive for 2011 September 22.

22 September 2011

More moki marbles

More moki marbles: little concretions in sandstone, kind of like the ones I showed you Tuesday from Illinois. But these ones are from the Navajo Sandstone, a late Triassic or early Jurassic erg deposit from the Colorado Plateau. These photos were taken in Zion National Park, near Springdale, Utah (real close to the cross-beds I featured a month ago). They are tougher than the sandstone in which they formed, and …

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