Grand Canyon - Slide Observations




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This page contains photographs of landscapes in the Grand Canyon and locations of samples.  

grand_canyon_angel.jpg (285713 bytes) Overview of the central Grand Canyon, looking northeast at Bright Angel Creek, with the Colorado River canyon in the lower foreground.  Zoroaster Temple is the prominent pointed butte in the top right of the photograph.

Exercise 9A - Mini-mysteries of the Grand Canyon

Each photograph contains a geologic mystery, such as a dike, unconformity, or other geologic feature.  Begin by drawing a generalized sketch of each photograph.  Identify on your sketch the geologic mystery contained in the photograph, and then solve the relative sequence of events that formed the scene you observe. Click on the small image to bring up a larger version.

hance_dike.jpg (139940 bytes) Precambrian rocks in the bottom of the canyon at Hance Rapids, eastern Grand Canyon. The lower red rock unit is siltstone and shale, and the upper rock is sandstone.  There is also a dark-colored igneous rock.  What are the relative ages of these three rocks?
stephen's_aisle.jpg (88559 bytes) Paleozoic rocks at Stephen's Isle, central Grand Canyon.  The bottom ledge is Tapeats Sandstone, representing an ancient beach, overlain by slope-forming Bright Angel Shale and Muav Limestone, with cliff-forming Redwall Limestone (contains corals) at the top on the right.  All four formations contain marine fossils.  What changes in the environment could account for this sequence of rocks?
upper_granite_gorge_unconformity.jpg (108991 bytes) Inner Granite Gorge, upstream from Phantom Ranch, central Grand Canyon.  The lower unit is dark Precambrian metamorphic rocks (Vishnu Schist) cut by pinkish granite dikes; the upper unit is Cambrian Tapeats Sandstone.  What is the sequence of events represented here, and what is the contact at the base of the sandstone?

Exercise 9B - Sample Locations

103_gc_sites.jpg (176890 bytes) Photograph showing sample locations.  View is toward the southeast.