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Identification and Classification of Sedimentary Rocks. Terrigenous Clastic Sediments and Rocks. No “Simple” Classification Scheme. Folk. FICHTER. Nichols. Descriptive Textural Classification: Ternary Plots (see appendix B in Fichter and Poche ) of

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identification and classification of sedimentary rocks

Identification and Classification of Sedimentary Rocks

Terrigenous Clastic Sediments and Rocks

siliciclastic rock classification texture
Descriptive Textural Classification:

Ternary Plots (see appendix B in Fichter and Poche) of

G (gravel >2mm) - S (2mm>sand> 0.063mm)- M (mud<0.063mm)

significance of gravel (>30%) min. transport energy


S (sand) - C (clay<0.004mm)- S (0.063mm>silt> 0.004mm)


Siliciclastic Rock Classification: Texture
textural nomenclature tc s
Textural Nomenclature – TC’s

Nichols, Fig. 2.5, p. 9

siliciclastic rock classification
Siliciclastic Rock Classification
  • Mineralogical Classification/terminology
    • Sand ----------->Arenites
    • CGL------------->Rudites
    • MDST----------->Lutites

textural term mineralogical term

  • Arenite (& Rudite) Petrology, Why?
    • Ease of analysis and sampling
    • Composition can be interpreted
mineralogical classification sandstone architecture
Mineralogical ClassificationSandstone Architecture
  • F-M-C-P
    • Framework Grains
      • > 0.05mm (particulate residues; larger than coarse-grained silt)
    • Detrital Matrix
      • < 0.05mm (clay, qtz, flds, -CO3, organics, oxides) chemical weathering products
    • Cement
      • post-depositional orthochemical components; ppt from circulating pore fluids (qtz,-CO3, clay, fldsp, oxides, zeolite, salts)
    • Pores;
      • Primary (up to ~40%) or 2ndary due to leaching/dissolution
mineralogical classification sandstone architecture9
Mineralogical ClassificationSandstone Architecture
  • Framework Grains:
    • relative abundance a function of mineral grain

Availability, Chemical Stability, Mechanical Durability

  • Anything Possible, most common:
    • Qtz :
      • mono, poly, ign, meta, qtzite, chert, volc, etc; mech & chem stable, abundant
    • Feldspar:
      • K-spar (sandine, microcline), Plag (Na-Ca), stains (Amaranth soln), abundance and mechanical stability (variable)
    • Rock Fragments:
      • all kinds (including limestone/dolomite RF’s) ; abundant, variable stability
mineralogical classification of sandstone architecture
Mineralogical Classification ofSandstone Architecture
  • Carbonate cement (calcite, dolomite, ankerite, siderite)
  • Clay minerals (kaolinite, illite)
  • Quartz
  • Feldspar (albite)
  • Zeolite
  • Authigenic Components
mineralogical classification primary sandstone architecture
Mineralogical ClassificationPrimary Sandstone Architecture
  • Framework Grains
    • Accessory Minerals:
      • Mica
      • ZTR; zircon, tourmaline, rutile: stable heavies
      • Unstable heavies: Amph, Pyx, Chl, Garn, Epid
      • carbonate allochems
      • non-detrital/orthochem; glauconite (iron-rich clay after fecal pellets) and phosphate (colophane, apatite); unusual oceanographic conditions
data plots and sandstone classification
Data Plots and Sandstone Classification
  • TC’s with >50% grains & > 0.05mm
    • Arenites Ternary Diagram Q - F - R(L)
      • Q= mono and polycrystalline (not chert) quartz
      • F= monocrystalline feldspar
      • R (L)= rock (or lithic) fragments

Normalized, 3 phase classification: Q=q/q+f+r; F=f/q+f+r; R=r/q+f+r

data plots and sandstone classification14
Data Plots and Sandstone Classification
  • Normalized, 3 phase classification
    • Q= q/q+f+r
    • F= f/q+f+r
    • R= r/q+f+r
  • 7 types of “normal” Arenites
    • others = “mineral” arenite, i.e. mica-arenite, magnetite-arenite
sandstone classification
Sandstone Classification
  • Complete Arenite name (Folk,Andrews, and Lewis, 1970):
    • (sorting term),
    • (size term):
    • (cement),
    • (prominent non-detrital grain type),
    • (prominent detrital acc grain type),
    • (named arenite)

e.g Moderately Sorted, Medium-grained:

Calcite Cemented, Glauconitic, Micaceous, Quartz Arenite

Fichter and Poche

interpretation of sandstone composition
Interpretation of Sandstone Composition:
    • a relative measure of how extensively and thoroughly a sediment (sand size and larger) has been weathered, transported and reworked toward its ultimate end product, quartz sand.