SEDIMENTOLOGY ARTICLES Archives

Stages/types of chemical changes in sedimentology

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

In sedimentary petrology and diagenesis, terms like neochemical, allochemical, protochemical and post chemical reactions are used to describe various stages or types of chemical changes. Term Timing Main Process Example Protochemical Very early (surface or shallow) Microbial activity, initial mineral formation Pyrite from sulfate reduction Neochemical Early diagenesis Authigenic mineral growth Dolomite replacing calcite Allochemical […]

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Zingg Diagram

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

Zingg diagram is used for the classification of clastic sediment grain shapes (pebbles) based on three orthogonal axes : long (a), intermediate (b), and short (c). Method : Grain shape is defined by the ratios – Uses :

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Dismicrite

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

Dismicrite is a type of micritic limestone that contains irregular patches or pockets of sparry calcite (coarse crystalline calcite) within a fine-grained micritic matrix. The term is derived from : Features or Properties of Dismicrite Texture : Fine grained (micritic) with sparry calcite patches. Composition : Mainly micrite (carbonate mud, CaCO3) with coarser sparry calcite

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Alizarin Red S Test for Dolomite and Calcite

GEO-ARTICLES, GEOCHEMISTRY ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

The Alizarin Res S Test is a staining technique used in petrology to distinguish between calcite and dolomite. How it works Procedure “If the rock contains both dolomite and calcite, only the calcite areas will stain red, while the dolomite remains unstained.” Applications of Alizarin Res S Test

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Mineralogical or Compositional Maturity

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

Sandstone maturity refers to the degree of weathering, sorting, and rounding of grains within a sandstone, as well as the composition of the rock. It’s a measure of how far the sand has been transported and reworked, reflecting the degree of sedimentary cycle. Maturity is assessed through both textural and compositional characteristics. Mineralogical maturity (also called as compositional

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Imbricate Structure

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

Imbricate structure (or imbrication) is a geological fabric seen in clastic sedimentary rocks—especially in conglomerates and gravels—where elongated or flat clasts (like pebbles) are stacked or aligned in a consistent overlapping pattern, much like fallen dominoes or roof shingles. Mechanism Imbrication occurs due to the directional flow of water or wind, which exerts force on

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Mud Cracks : Desiccation and Syneresis Cracks

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

Mud cracks are the fracture patterns that formed in the muddy sediments, in sub-aerial environment. They are of two types :- Desiccation Cracks Syneresis Cracks Why are mud cracks important ?

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Stages of Diagenesis of Sandstone

GEO-ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

On the basis of mineral replacement and intergrowths, four oxide series are recognized among the sandstones – Stages of diagenesis From the type of reaction and the principal sequence of occurence three stages of diagenesis are established as follows – Among sandstones, the progress of diagenesis may be arrested at either the locomorphic or phyllomorphic

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Chemical Weathering and its type

GEO-ARTICLES, GEOCHEMISTRY ARTICLES, GEOMORPHOLOGY, SEDIMENTOLOGY ARTICLES / opengeology

Chemical weathering may be defined as the spontaneous and irreversible thermodynamic process that causes degradation of the mineral phases under the prevailing environmental conditions at the surface of the Earth. It is usually considered to be the solid/solution interactive process occurring in contact with the atmosphere. In other words chemical weathering may be defined as that set of processes

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HJULSTROM’S DIAGRAM

OCEANOGRAPHY ARTICLES, SEDIMENTOLOGY ARTICLES / opengeology

This plot shows the average current velocities necessary for the erosion, transportation and deposition of the sediment particles of different sizes. The lower curve on the diagram, it shows that once eroded and moving a clay particle, but not a fine particles of sand can be transported by a week current. This is because the

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