Tuesday, December 28, 2010

2008 Day 5 - Sept 17 mile 93-107 Salt to Conquistador Aisle

2008 Day 5 - Sept 17 mile 93-107 Salt to Conquistador Aisle

Mile 93 we are looking ahead towards Granite Rapid

Mile 93.5 looking back at Rob running Granite Rapid

Mile 98.2 we see Zoroaster dikes in the darker metamorphic rock amphibolite.
The Early Proterozoic rocks in this area are generally lower in metamorphic grade (lower amphibolite series or facies) than those upstream.
Oh yes, with an imagination you might read letters into the dike as NY or perhaps even I heart NY

Mile 98.8 After Tuna Rapid looking ahead towards Lower Tuna (Willies Necktie) Rapid - Fantastic detail in the granite here!
Tapeats overlies Vishnu and Zoroaster in a nonconformity. Redwall Limestone caps the right "claw" of Scorpion Ridge above

Mile 98.8 detail of nonconformity

Mile 99.9 Rob passes Nixon Rock (large granite island)

Mile 102 looking upstream in the Gems (ASTER Agate, Sapphire, Turquoise, Emerald, Ruby) relatively narrow gorge

Mile 104 looking toward Emerald Rapid we see a north rim temple ahead - we see Ruby Creek Pluton granitic rocks thru here

Mile 106 view downstream from roughly a mile above Bass Rapid

Mile 107 we see the Ruby Pluton rounded granodiorite rocks at right (we temporarily left the intrusions of pink granite behind upriver).  The Ruby Pluton - part of Ruby Creek Superunit - extends from around Mile 103 past this point but is the last pluton we will see in the granite gorge.

Ahead is Bass Rapid along with Powell Plateau on the left skyline
This is a geologic feature rich view - see the Grand Canyon Supergroup ahead - we will look closer at several features in this area next

End of Part 1 - Day 5 to be continued

Mile 107 the Powell Plateau is visible ahead on the skyline

Wayne's tree is discussed and spotted - here is a detail (the tall tree all by itself)


A later even clearer detail (shot around mile 110)

Mile 107 we note the granite gorge go under water on the left - probably the same fault returns the Supergroup ahead - the granite will return within a couple miles

Here is a panorama with more Supergroup detail

Mile 107.5 shortly before the Ross Wheeler we see Dox Castle ahead on river right (right skyline) - notice other Supergroup  below and middle skyline.
Dox Castle is the type locality for Dox Formation and was named by William Bass after Virginia Dox (the first female visitor he guided in the grand canyon).  Thanks to Wayne for identifying this photo and providing the geo-history via email after the trip.
Link to another photo from the esplanade of Dox Castle on the web.

Here is a panorama extending from Powell Plateau on left skyline to Dox Castle on right skyline - lots of Supergroup in between

Mile 108.x the Grand Canyon Supergroup is visible for the next few miles due to faulting (we will see other evidence of faulting)
In this area we see Hotauta Conglomerate, Bass Limestone, Hakatai Shale, Shinumo Quartzite, and Dox Formation.

Mile 108.6 Shinumo Creek (type locality for Shinumo Quartzite) has a nice cooling waterfall


View above Shinumo Creek Canyon

Mile 109 View northwest towards the Redwall-capped Fan Island (on middle skyline). The Tapeats ends abruptly against a Shinumo island below and right of Fan Island (the Shinumo Island prevented deposit of Tapeats as it was above sea level during Tapeats time - similar to the double Shinumo island visible on the Clearcreek trail discussed in "Hiking The Grand Canyon's Geology" page 143).

Mile 110 we look ahead to 110 Mile Rapid

Mile 113 we see a large rock in mid-river creatively named 113 Mile Rock - known by some at ARTA in the 70s as Rancid Tuna Fish Sandwich Rock

Mile 113 Vishnu Bedrock Mid Channel

Mile 115 in the Garnet Canyon area we look up at a Tapeats stack on top of a favorite section of granite gorge with some nice vertical dikes at lower left/
At the lower right the dark Elves Chasm Granodiorite/Gneiss is the oldest dated rock in Arizona (at 1840 Ma) and represents a metamorphosed granodiorite pluton even older than the oceanic sediments and lavas of the Vishnu, Brahma, and Rama units. It is thought to be similar in age and composition to the Trinity Gneiss.  Note the light-colored dikes of the Garnet Pegmatite Suite
Here is a link discussing metamorphic facies showing the relationship of temperature and pressure (and therefore depth) to which metamorphic rocks were formed.

Mile 115 Light colored dikes intrude Elves Chasm Pluton (nicely exposed at river level)

Mile 115.9 we observe a fault in the Tapeats (this is a monocline as the Tapeats is not impacted left or right of the fault)
This dates from the Laramide Orogeny and is about the same age as the Butte fault.
First photo is river left where the displacement is most pronounced.

Here is the same fault directly across on river right

Mile 116 we observe (on river left) more travertine deposits and finally several massive Travertine deposits discussed by Wayne (also notice the many caves we expect to see where water flows thru and out of the red wall limestone

detail of travertine "ooze"

End of Part 2 - Day 5 to be continued

Mile 116.5 we hike up to Elves Chasm waterfall - brief coverage here (covered in depth by Sueann)

Dock at Elves beach

Hiking up - easy hike with one boulder move - nice pool of water to cool off in

We soon reach the water fall - First view

Wait - there is a rattle snake on the rock - it is trapped by the cold water

Here he has been freed by Ed

Mile 117 we are in Stephen Aisle with Tobar Terrace at top right skyline and Elves Chasm Pluton rocks still visible at river level - in the distance ahead is the northwest wall of Blacktail Canyon

At around mile 118 we see the Granite Gorge disappear under water (again) and notice Alarcon Terrace on the skyline (see the distinctive rock formation)

Alarcon Terrace details (we are looking ahead several miles as the terrace is actually at river mile 122.5 above one hundred twenty two mile creek, near where we will camp tonight).


Lastly, that cool rock formation - seen on every river trip

Mile 119.9 we hike up Blacktail Canyon (great Tapeats stack visible below)

Wayne lectures on the Great Unconformity (just behind him) and reviews a map from his new book showing how the area looked at the time it was formed


Detail of Great Unconformity

Also in Blacktail Canyon Rob showed us how a quartzite boulder had fallen off a cliff and broken into pieces into the Tapeats "ooze" as it was forming - this is now embedded in a large Tapeats boulder in Blacktail Canyon

Detail of the inclusion

with hat for scale (and wetted for clarity)

We camped on river left in Conquistador Aisle around mile 122 (unnamed campsite near Forster Canyon) 

Sueann and I hiked up and contoured downstream- here is a view down on the campsite

Here is a shot looking upstream from a few hundred feet above our campsite (tiny spot at lower left)

And after contouring at the same height downstream a little here is a shot of Forster Rapid

I turned around here but Sueann continued hiking up to just below the redwall

End of Part 3 - Day 5 done

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