Diagenesis/Textures Flashcards
Encompasses a suite of low temperature processes that affect sediments after their accumulation, typically after burial.
Diagenesis
A process of lithification that results from the expulsion of intergranular fluids caused by increases in confining pressure during progressively deeper burial.
Compaction
A process of lithification that occurs when subsurface fluids precipitate minerals in the spaces between grains that bind or cement grains to one another.
Cementation
What are the major cements of sedimentary rocks?
- Silica Minerals
- Carbonate Minerals
- Iron oxides and hydroxides
- Feldspars
- Clay Minerals
What is the most abundant silica cement?
Quartz
What is the most abundant cement in sandstones and gravelstones?
Carbonate minerals
What is the most abundant carbonate cement?
Calcite
What is the third most common cementing agent in sedimentary rocks?
Iron oxides and hydroxides
Chief iron oxide and hydroxide cements
Hematite, goethite, and limonite
Stages of Diagenesis
Eodiagenesis
Mesodiagenesis
Telodiagenesis
Early, shallow diagenesis that
occurs shortly after burial.
Eodiagenesis
- Later, deeper diagenesis.
Mesodiagenesis
Still later, shallow diagenesis
that occurs as sedimentary rocks approach the surface due to erosion.
Telodiagenesis
Enumerate the texture parameters of sedimentary rocks.
- Grain Size
- Grain Shape
- Grain Orientation
- Porosity
- Permeability
A classification scheme that describes sediments’ particle sizes in epiclastic rocks. It also classifies particles sizes based on a logarithmic phi scale using the diameter (d)
Grain Size
Φ = -log₂d
A texture parameter of sedimentary rocks that determines or gives information regarding the nature or maturity of a grain.
Grain Shape
What are the two factors affecting shape?
- Lithology
- Hardness
Also known as the coarse fraction, is the component of detrital sedimentary rocks that have particles sizes from sand to gravel.
Clasts
Also known as the fine fraction, is the mud- sized particles component of detrital sedimentary rocks.
Matrix
A measure of particle population in an attempt to represent the typical particle size in the population.
Central Measure
A bar graph that shows the weight percentage vs. phi values of clasts.
Histogram
A line graph that shows the weight percentage vs. phi values of clasts.
Frequency Curve
A line graph that shows the cumulative weight percent of all size coarser than, including the phi size fraction under consideration, are plotted against phi size classes.
Cumulative curve
A method of passing soil and sediment samples through a series of stacked mesh to determine the distribution of grain sizes.
Sieving
