Study Guide for Exam 2

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Northern Virginia Community College *

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106

Subject

Geology

Date

Dec 6, 2023

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docx

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3

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How is strata different from stratigraphy? Which type(s) of rock most commonly form strata? Can igneous rock form in layers? How? Interpret the following statement: "The data is in the strata." What is the “craton”? Which type of rock(s) typically form the “basement” rock of the craton? What are facies? Review the following video as many times as it takes until you fully understand the concepts. Facies video The following are the lateral progression of facies in a siliciclastic environment. Terrestrial → Shoreline → Nearshore → Offshore Gravel → Coarse sand → Fine Sand → Silt → Clay Conglomerate (Cg) → Coarse sandstone (Css) → Fine Sandstone (Fss) → Siltstone (Ss) → Shale (Sh) The following are the lateral progression of facies in a mixed siliciclastic/carbonate environment. Terrestrial → Shoreline → Nearshore → Offshore → Open Shelf Gravel → Coarse sand → Fine Sand → Silt → Clay → Lime mud Conglomerate → Coarse sandstone → Fine Sandstone → Siltstone → Shale → Limestone (Ls) What is Walther’s Principle? What does a lithofacies map display? What is a rock formation ? What is a lithostratigraphic unit? What is a geologic contact between sedimentary strata? What is an epicontinental sea? What environmental conditions lead to the formation of epicontinental seas? What is a foreland basin? Marine Important to note that not all of these layers need to be present to indicate
transgression: Ls Sh Ss Fss Css Cg a transgression or regression. The following sequences would also be recognized as a marine transgression: Limestone Shale Shale Sandstone Sandstone Conglomerate The important characteristic to note is that the sediments become finer in the vertical sequence (bottom to top) in a transgression. This is a fining upward sequence . Marine regression: Cg Css Fss Ss Sh Ls Important to note that not all of these layers need to be present to indicate a transgression or regression. The following sequences would also be recognized as a marine regression: Sandstone Conglomerate Shale Sandstone Limestone Shale The important characteristic to note is that the sediments become coarser in the vertical sequence (bottom to top) in a regression. This is a coarsening upward sequence. What does the color or sedimentary rocks tell us about the environment of deposition? (Low oxygen = darker color; red/yellow/orange = high oxygen and oxidation of iron) What is an unconformity? Know the different types of unconformities and how we recognize them. (Angular unconformity; nonconformity; disconformity). Review the principles of relative dating: superposition, lateral continuity, horizontality, cross- cutting, inclusions, faunal succession What is the fossil record ? How is it related to the rock record ? Be able to recognize and identify the different types of fossilization. What is an index fossil? What is the geologic range of a given organism? What is a fossil assemblage? Evolution vocabulary and concepts: Darwin and Wallace Natural selection
Genetic mutations (and how they occur) Artificial selection Adaptation What defines a species? Speciation Descent with Modification
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