Tuesday, March 3, 2009

gigapan: verde outcrop


I took my first Gigapan of one of the outcrops we visited on our Club field trip to the Sedona area last weekend .
Paul Lindburg lead us on another great trip-- his third. This outcrop is important in explaining the origin of the Verde Valley.
Check the whole outcrop here:

gigapan: verde outcrop


This is a labeled detail view of the faulting.
Pz is the red Permian Supai Sandstone which was deposited first.
Across the normal fault on the downdropped side are the Tertiary Volcanics from the House Mountain Volcano (Miocene) which overlay the Supai.
On top of the Permian is Gravel 1 which was transported to the north carrying clasts from the highlands in central Arizona. These deposits include include Paleozoic and Mazatzal gravels derived from the south, indicating they were deposited when the Bradshaw Mountains were much higher and rivers flowed to the north and northeast in the opposite direction from today.
On top of the entire outcrop and younger than the faulting is Gravel 2 which was transported to the west towards the center of the Verde Grabben. It contains clasts from both the underlying Tertiary House Mountain basalt and the Supai in a red matrix of mud and sand.
The conclusion from this outcrop is that the formation of the Verde Valley Grabben occurred during the Basin and Range Extentional Orogeny (6 m.a. more or less) and after the the Eruption of the Volcanics from House Mountain (aprox 13m.a.).
Harry Allen


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