ERT 02 06 Lab Report final 1
Date: November 17th, 2014
Answer the questions below. When you are finished, submit this assignment to your teacher by the due date for full credit.
In this laboratory experiment, you will write a narrative history of a rock section found in the Grand Canyon. You will describe and explain the events starting with the Vishnu Schist forming and ending with the unconformity above the Redwall Limestone in the Mississippian. Your description should include environmental changes.
Sea level lowered, and the Esplanade Sandstone was deposited in a beach environment.
Erosion, and the sea level rose.
Hermit Shale deposited in a deeper sea.
Sea level drops, returning the area to a beach environment where the Coconino Sandstone was deposited.
1. Interpret the bottom half of the cross section below. Start with the Vishnu Schist and end with the Redwall Limestone.
Correct order: Redwall limestone, Temple Butte Limestone, Muav Limestone, Bright Angel Shale, Tepeats Limestone, Dox Sandstone, Shinumo Quartite, Hakatar Shale, Igneous intrusion, Bass Limestone, Vishnu Schist.
Proper environmental changes: The environment starting from Redwall Limestone is warm and shallow seas, then deep seas, then beaches, then rocks start melting then recrystallize, then rocks are severely deformed without melting, this section represents the original surface in the area.
Attention to detail and completeness: The Redwall Limestone layer is formed by red stained cliffs that range in height from 550 feet to 900 feet. It is a deeply eroded dis conformity by deeply incised paleovalleys and deep paleokrast. The Temple Butte Limestone is formed by discontinuous lenses, and relatively inconspicuous lenses that fill paleovalleys cut into the underlying Muav Limestone. Consists of a westward thickening layer of inter bedded dolomite, sandy dolomite, sandstone, mud stone, and limestone that vary in color. Bright Angel Shale was formed by green and purple-red siltsone and shale which is inter bedded with red-brown to brown sandstone that is similar in lithology to Tapeats. Tapeats Limestone is formed by highly erosion-resistant unit laid upon the Vishnu Basement Rocks. Dox Sandstone is formed by mesoproterzoic rock that are relatively susceptible to erosion and weathering. Vishnu Schist is formed by the cyrstalline basement rocks that underlie the Bass Limestone of the Unkar Supergroup and the Tapeats Sandstone of the Tonto Group.
2. There is one of each type of unconformity in this diagram. Name at least one of each of them by indicating the layers that they are between.
Nonconformity: The nonconformity layer is Mauv Limestone I know this because it is the one that goes into Temple Buttte Limestone.
Angular unconformity: The Angular Unconformity layer is the Shunumo Quartzite, Hakatar Shale and Bass Limestone. I know this because they are the only 3 going at an angle.
Disconformity: The Disconformity layer is Redwall Limestone because it is the only layer that droops down.
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Beach or nearshore environment
Forms in warm shallow seas
Formed when rocks melt and then recrystalize
Formed when rocks are severely deformed without melting; in this cross section, the Vishnu Schist represents the original surface in the area
Magma melting and rising from deeper levels
Hint: How can you tell the difference between an intrusion and rocks melting in place? Rocks melting in place usually appear as a large mass, whereas intrusions seem to have risen up from a source.