Rock descriptions distractions small

Sedimentary Rock Descriptions and Distractions

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

Text: Manual, p. 13-16, 77-90; Compton, p. 27-31


Rock Descriptions
• stratigraphic name
• rock type


Rock Descriptions
• stratigraphic name
• rock type
• color


(Luis Garcia)


Rock Descriptions
• stratigraphic name
• rock type
• color
• texture

Rock Descriptions
Texture: 1. Grain Size
mm
256
64
4
2
1
0.5
0.25
0.125
0.0625
0.031
0.0156
0.0078
0.0039
⇓

Phi (φ)
-8
-6
-2
-1
0.0
1.0
2.0
3.0
4.0
5.0
6.0

7.0
8.0
⇓

Wentworth Size Class
boulder
cobble
pebble
granule
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
coarse silt
medium silt
fine silt
very fine silt
clay

gravel
_______
sand
_______
mud


Rock Descriptions
Texture: 2. Grain Shape (Roundness)
angular grains

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well rounded grains


Rock Descriptions

Texture: 3. Sorting


Rock Descriptions
Texture: 4. Arrangement

imbrication

(AGI, 1999)


Rock Descriptions

Texture Interpretations
• energy/environment of deposition
• transport history


Rock Descriptions
• stratigraphic name
• rock type
• color
• texture

• grain composition


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


Rock Descriptions
grain

porosity
cement

matrix

(M. Campbell)


Rock Descriptions
• name
• rock type
• color
• texture
• grain composition

• porosity
• cements
• bedding


Rock Descriptions
Bedding: Types

10 cm

laminations
Castile Formation, NM (Anderson et al., 1972)


Rock Descriptions
Bedding: Types

cross-bedding


Rock Descriptions

Bedding: Types

(AGI, 1999)

graded bedding


Rock Descriptions

Bedding: Thickness


Rock Descriptions
Bedding: Contacts


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


Rock Descriptions
Sedimentary Structures

wave ripples


Rock Descriptions
Sedimentary Structures

burrows

Rock Descriptions

Sedimentary Structures

(AGI, 1999)

mudcracks


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


Rock Descriptions
Bioturbation

(E. McBride)