Lec-1&2

Outline of Sedimentary Petrography

  1. Historical Introduction

    • Organized study began with thin-section techniques and polarizing microscope.

    • Henry Clifton Sorby noted for thin-section work in 1849, focused on calcareous sediments.

    • Contributions summarized by Folk (1965) and Sumerson (1978).

    • Thin-section aims to read rock history (mineral composition, fabric, porosity).

  2. Rock Description and Analysis in Field

    • Description from outcrops, cores, specimens, and thin sections.

    • Thin sections prepared easily for unconsolidated sands (Middleton and Kaurus, 1980).

    • Field studies key on lithology, grain size, texture, fossil content.

    • Observe and gather samples for paleocurrent analysis (Green Smith, 1980).

  3. In the Laboratory

    • Reveals sedimentary structures not visible in the field.

    • Techniques: cutting, polishing, acid etching, staining.

    • Grain size measured via sieves; heavy minerals with bromoform.

    • SEM for high magnification, especially for fine-grained/clay minerals (Gartner et al., 2013).

  4. Sedimentary Petrography

    • Analyzing depositional and diagenetic fabrics; includes mineral composition and grain size.

    • Quantitative or qualitative techniques focused on depositional and diagenetic fabrics.

  5. Petrographic Report by Folk (1974)

    1. Samples identification: formation name, age, geographic data.

    2. Field Relations: thickness, position, boundaries, lithologies.

    3. Handspecimen Description: color, grain size, sorting, composition.

    4. Thin-section Summary: texture, fabric, angularity, sphericity.

  6. Classification of Sedimentary Rocks

    • Sandstones categorized via point counting for modal analysis (Folk, 1974).

    • Main types: Arenite, Wacke, Graywacke by matrix proportion.

  7. Detrital Components of Siliciclastic Sediments

    • Framework grains (e.g., quartz, feldspar) and finer-grained matrix.

    • Authigenic minerals and cement from diagenesis.

    • Chemical stability affected by weathering processes.

  8. Matrix & Cement

    • Matrix: Fine-grained material between larger grains.

    • Cement: Minerals binding grains; includes silica, carbonates, oxides.

  9. References

    • Coherent list of significant literature from leading authors in sedimentary petrology.