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

• rock type

• stratigraphic name

Rock Descriptions

• stratigraphic name

• rock type

• color

(Luis Garcia)

Rock Descriptions

• stratigraphic name

• rock type

• color

• texture

Rock Descriptions

Texture: 1. Grain Size

256 -8 boulder64 -6 cobble gravel4 -2 pebble2 -1 granule _______1 0.0 very coarse sand0.5 1.0 coarse sand0.25 2.0 medium sand sand0.125 3.0 fine sand0.0625 4.0 very fine sand _______0.031 5.0 coarse silt0.0156 6.0 medium silt mud0.0078 7.0 fine silt0.0039 8.0 very fine silt clay

mm Phi () Wentworth Size Class

angular grains

well rounded grainshttp://csmres.jmu.edu/geollab/Fichter/SedRx/

Rock Descriptions

Texture: 2. Grain Shape (Roundness)

Rock Descriptions

Texture: 3. Sorting

(AGI, 1999)

Rock Descriptions

Texture: 4. Arrangement

imbrication

• energy/environment of deposition

• transport history

Rock Descriptions

Texture Interpretations

Rock Descriptions

• stratigraphic name

• rock type

• color

• texture

• grain composition

Rock Descriptions

• stratigraphic name

• rock type

• color

• texture

• grain composition

• porosity

• cements

grain

porosity

matrix

cement

(M. Campbell)

Rock Descriptions

Rock Descriptions

• name

• rock type

• color

• texture

• grain composition

• porosity

• cements

• bedding

Rock Descriptions

Bedding: Types

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

10 cm

laminations

Rock Descriptions

Bedding: Types

cross-bedding

Rock Descriptions

Bedding: Types

graded bedding

(AGI, 1999)

Rock Descriptions

Bedding: Thickness

Rock Descriptions

Bedding: Contacts

Rock Descriptions

• stratigraphic name

• rock type

• color

• texture

• grain composition

• porosity

• cements

• bedding

• sedimentary structures

wave ripples

Rock Descriptions

Sedimentary Structures

Rock Descriptions

burrows

Sedimentary Structures

Rock Descriptions

Sedimentary Structures

mudcracks

(AGI, 1999)

Rock Descriptions

• stratigraphic name

• rock type

• color

• texture

• grain composition

• porosity

• cements

• bedding

• sedimentary structures

• bioturbation

Rock Descriptions

Bioturbation

(E. McBride)

Rock Descriptions• stratigraphic name

• rock type

• color

• texture

• grain composition

• porosity

• cements

• bedding

• sedimentary structures

• bioturbation

• fossils

Trace Fossils

Rock DescriptionsFossils

Body Fossils

Cretaceous fossils in central Texas

http://www.cretaceousfossils.com

Rock Descriptions

Fossils

UTAUSTIN

Interpretation

Rock Descriptions

Additional Details for Sandstones:

- FMCP:QFR

- Clan Name

Rock Descriptions

Sandstone Clan Names

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

Unit Descriptions

• stratigraphic name

• rock types

• brief rock descriptions

- percentages- thicknesses

- contacts- interbedding

• special features

- soil and vegetation- topographic expression

gradational

sharp

interbedding

Unit Descriptions

bench

slopecliff

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

Distractions

Vegetation

(Luis Garcia)

Distractions

Algae

Distractions

Lichen

Distractions

Travertine

(E. McBride)

Distractions

Weathering

Distractions

(E. McBride)

Colluvium

Distractions

Float

(E. McBride)

Distractions

Dynamite

(E. McBride)