HEY! WHO STOLE MY ROCKS? WHERE
IN THE GRAND CANYON ARE THE
MESOZOIC AND CENOZOIC STRATA?
Dr. Melissa K. Giovanni
Outline
 What’s so special about the Grand Canyon anyways??
 Meso-what? A brief intro to the geologic time scale
 Reading the “pages” of the Grand Canyon
 Plate Tectonics – where did these rocks come from and
where are they going?
 Paleogeography of Grand Canyon strata
 The Colorado Plateau and those “missing” rocks
Why is the Canyon so special?
Only place on Earth where you can look 2 billion years back in time…
…while standing still.
A Brief History of Time
(apologies to Stephen Hawking)
The Geologic Time Scale (to scale)
Divisions of Time
Eon  Era  Period  Epoch
“-zoic” – relating to animal life
Proterozoic - “pre/early life”
Phanerozoic - “visible life”
Paleozoic – “ancient life”
Mesozoic – “middle life”
Cenozoic – “recent life”
It’s all about perspective
“Reading” the Grand Canyon
Sedimentary Rocks & The Rock Cycle
How to Read the Grand Canyon “Book”
The Principle of Original Horizontality states that because
sediments settle out of a fluid by gravity, they tend to accumulate
horizontally. Sediment accumulation is not favored on a slope.
Hence, tilted sedimentary rocks must be deformed.
How to Read the Grand Canyon “Book”
The Principle of Superposition states that in an
undeformed sequence of layered rocks, each bed is
older than the one above and younger than the one
below. Younger strata are on top; older strata are below.
Erosion and Unconformities
The “pages” of the Grand Canyon
270 Ma
275 Ma
320-280 Ma
350 Ma
525-505 Ma
1700 Ma
Whence the rocks?
Where did the Phanerozoic strata come from?
Paleozoic – found in Grand Canyon
Mesozoic & Cenozoic – the “missing rocks”
It’s all about the plates.
Plate Tectonics
Earth’s surface is constantly changing
Plate Tectonics
Earth’s surface is constantly in motion
Plate Tectonics
Earth during the past 600 million years
https://www.unavco.org/software/visualization/idv/display_images/RBlakey-paleoglobe-flatmap-600Ma-movie.gif
Paleogeography of the Grand Canyon
Time slices reconstructing landscape and
tectonic environment of the Grand Canyon
region.
© Ron Blakey, Colorado Plateau Geosystems
cpgeosystems.com
Paleozoic – 525 Ma
Paleozoic – 470 Ma
Paleozoic – 430 Ma
Paleozoic – 370 Ma
Paleozoic – 340 Ma
Paleozoic – 310 Ma
Paleozoic
280 Ma
Those are the rocks & environments preserved
and exposed in the Grand Canyon…
... but what about those “missing rocks”?
Mesozoic
Ma(between Valle & Tusayan)
Red245
Butte
Cedar Mtn from Desert View
Gold Hill from Desert View
http://www.kaibabjournal.com/Grand_Canyon_Trips/2
005_04_13_old_tanner/2005_04_13_577_cedar_mtn.jpg
http://www.rockhounds.com/grand_hikes/geology/overview.shtml
http://www.fs.usda.gov/recarea/kaibab/recreation/recarea/?recid=11684&actid=50
Mesozoic
215 Ma
https://mrgrosky.files.wordpress.com/2008/10/vermillion-ciffs-in-arizona.jpg
http://ramcquade.com/?tag=vermillion-cliffs-national-monument
Mesozoic
180 Ma
Mesozoic
150 Ma
Mesozoic
125 Ma
Mesozoic
90 Ma
Mesozoic
70 Ma
Cenozoic
50 Ma
Cenozoic
35 Ma
Cenozoic
20 Ma
Cenozoic
15 Ma
Cenozoic
10 Ma
Cenozoic
5 Ma
Cenozoic
0 Ma
Why are the Meszoic & Cenozoic rocks
missing from the Grand Canyon??
Laramide Orogeny
http://www.geo.arizona.edu/geo5xx/geo527/Rockies/flatsub.html
Why are the Meszoic & Cenozoic rocks
missing from the Grand Canyon??
So where are those Mesozoic & Cenozoic rocks??
The Colorado Plateau
The Colorado Plateau
The national parks of Arizona and Utah provide an excellent case history of stratigraphic
correlation. The formations in the region are readily identified and can be traced over long
distances. Overlap is seen in the sequences of rock types, and these overlapping rock columns
can be used to build a composite.
The Colorado Plateau
Thank you
http://www.sociolatte.com/2014/12/sunrise-and-sunset-over-grand-canyon.html