The Great Unconformity - One Billion Years of Rock Gone Missing
Like a great wall, the vertical cliffs that mark the Tapeats Sandstone cap, ~500 million years old, atop the Precambrian Vishnu Schist (~1.5 billion years old) run like a ribbon through this scene, starting at the left center. A combination of severe tilting of the older layers and erosion of the intervening strata have either buried or stripped away 1 billion years of geologic record.
Such unconformities (gaps in the rock record) occur in many other places around the world. The one on display in the Grand Canyon is one of the more spectacular examples, earning it the name 'Great Unconformity', awarded to it by John Wesley Powell in the 19th century. Strictly speaking (according to Wikipedia), the juxtaposition of the Tapeats sandstone directly atop the Vishnu schist is a nonconformity, rather than an unconformity.
DP091-2015 Posted Wednesday, April 1
Looking downstream (south and west) from a point a few miles downstream from the confluence of the Little Colorado River with the Colorado River. The massive wall of dark stone on the left (south) bank is Vishnu schist, the only metamorphic layer exposed in the canyon, and also the oldest. If you're a geology nut like myself, read more about the phenomenon online, certainly, and in books (what a concept!).
Title: The Great Unconformity - One Billion Years of Rock Gone Missing
Taken March 29, 2008, during a scenic flight over the Grand Canyon.
arctangentdailyphotosdpD091posted 2015post 775posted April 1WednesdaytravellandscapeGrand CanyonNational Parksouth rimscenic flightaerialaerial photographColorado RiverGreat UnconformitygeologyVishnu schistTapeats sandstonemetamorphicsedimentarylayersstratacolorsnaturearctangent, from