Classification of Sandstone - Sedimentology - Lecture Slides, Slides of Geology

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Classification of Sandstone

Objectives :

1. To classification of sandstone rock.

2. To identification of the source rock and

tectonic relation.

As a secondary criterion the classification distinguishes between the clean-sands (arenites); sands with less than 15% matrix, and the dirty- sands (wackes); those with more than 15% matrix.

Arenite

Wacke (^) 5

General description

1. Quartz arenites:
   1. The detrital fraction is 95% or more quartz
   2. Are generally white rocks
   3. Minerlogically and texturally is mature
   4. As tectonism interpretation is passive
   5. Transportation take to large distance
   6. Have more sorting and roundness
   7. Silica is the most common cementing agent

Quartz arenites:

2. Arkosic arenites:
   1. Those with 25% or more feldspar and smaller percent of rock fragments
   2. Generally appear as pink color
   3. Minerlogically immature (due to more than 25% of feldspar, unstable mineral), but texturally is mature (due to matrix" clay" content less than 15%).
   4. As tectonism interpretation is active
   5. Transportation take to small distance
   6. Have bad sorting and angular.

Arkosic arenites:

3. Lithic arenites:
   1. With an abundance of rock fragments, especially of sedimentary, low rank metamorphic and volcanic rocks,
   2. Subangular to rounded quartz, and with a chemical cement, either quartz or silica.
   3. Generally light grey,
   4. Immature due to low transported distance.
   5. Near the source area.
   6. As tectonism interpretation is high tectonic activity.
   7. Have bad sorting and subangular. (^13)

Lithic arenites:

For those sandstones with a significant matrix content (15%) the general term wacke has been used. These are dominantly the graywackes.

4. Graywackes:
   1. Is a tight enough rock because of high matrix(more than 15% ).
   2. Generally dark grey to black color
   3. In general mineralogically and compositionally is immature due to rapid deposition and uplifting.
   4. Near the source area.
   5. As tectonism interpretation is high tectonic activity.
   6. Have bad sorting and subangular.