Sedimentary Rock Descriptions and Distractions

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Sedimentary Rock Descriptions and Distractions

• Description vs Interpretation
• Rock Descriptions
• Unit Descriptions
• Distractions

Text Manual, p. 13-16, 77-90 Compton, p. 27-31
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Rock Descriptions

• stratigraphic name

• rock type

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Rock Descriptions

• stratigraphic name
• rock type
• color

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(Luis Garcia)
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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture

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Rock Descriptions
Texture 1. Grain Size
mm Phi (?) Wentworth Size Class
256 -8 boulder 64 -6 cobble gravel 4 -2 pebbl
e 2 -1 granule _______ 1 0.0 very coarse
sand 0.5 1.0 coarse sand 0.25 2.0 medium
sand sand 0.125 3.0 fine sand 0.0625 4.0 very
fine sand _______ 0.031 5.0 coarse
silt 0.0156 6.0 medium silt mud 0.0078 7.0 fine
silt 0.0039 8.0 very fine silt ? ?
clay
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Rock Descriptions
Texture 2. Grain Shape (Roundness)
angular grains
well rounded grains
http//csmres.jmu.edu/geollab/Fichter/SedRx/
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Rock Descriptions
Texture 3. Sorting
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Rock Descriptions
Texture 4. Arrangement
imbrication
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Rock Descriptions
Texture Interpretations

• energy/environment of deposition
• transport history

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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture
• grain composition

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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture
• grain composition
• porosity
• cements

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Rock Descriptions
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Rock Descriptions

• name
• rock type
• color
• texture
• grain composition
• porosity
• cements
• bedding

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Rock Descriptions
Bedding Types
10 cm
laminations
Castile Formation, NM (Anderson et al., 1972)
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Rock Descriptions
Bedding Types
cross-bedding
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Rock Descriptions
Bedding Types
(AGI, 1999)
graded bedding
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Rock Descriptions
Bedding Thickness
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Rock Descriptions
Bedding Contacts
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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture
• grain composition
• porosity
• cements
• bedding
• sedimentary structures

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Rock Descriptions
Sedimentary Structures
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Rock Descriptions
Sedimentary Structures
burrows
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Rock Descriptions
Sedimentary Structures
(AGI, 1999)
mudcracks
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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture
• grain composition
• porosity
• cements
• bedding
• sedimentary structures
• bioturbation

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Rock Descriptions
Bioturbation
(E. McBride)
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Rock Descriptions

• stratigraphic name
• rock type
• color
• texture
• grain composition
• porosity
• cements
• bedding
• sedimentary structures
• bioturbation

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Rock Descriptions
Fossils
Trace Fossils
Body Fossils
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Rock Descriptions
Fossils
Cretaceous fossils in central Texas
http//www.cretaceousfossils.com
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Interpretation
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Rock Descriptions
Additional Details for Sandstones -
FMCPQFR - Clan Name
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Rock Descriptions
Sandstone Clan Names
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Sedimentary Rock Descriptions and Distractions

• Description vs Interpretation
• Rock Descriptions
• Unit Descriptions
• Distractions

Text Manual, p. 13-16, 77-90 Compton, p.
27-31, 366-367
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Unit Descriptions

• stratigraphic name
• rock types
• brief rock descriptions
• - percentages
• - thicknesses
• - contacts
• - interbedding
• special features
• - soil and vegetation
• - topographic expression

interbedding
gradational
sharp
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Unit Descriptions
cliff
slope
bench
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Sedimentary Rock Descriptions and Distractions

• Description vs Interpretation
• Rock Descriptions
• Unit Descriptions
• Distractions

Text Manual, p. 13-16, 77-90 Compton, p.
27-31, 366-367
36
Distractions
Vegetation
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Distractions
Algae
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Distractions
Lichen
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Distractions
Travertine
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Distractions
Weathering
(E. McBride)
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Distractions
Colluvium
(E. McBride)
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Distractions
Float
(E. McBride)
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Distractions
Dynamite
(E. McBride)