Sedimentary Rocks Classification Flashcards

Questions and Answers

What are the 4 types of sedimentary rocks?

Igneous

Chemical (correct)

Clastic (correct)

Biochemical (Biogenic) (correct)

What are clastic sedimentary rocks composed of?

Silicate minerals and rock fragments that were transported and deposited.

What do clastic rocks typically contain?

Quartz, feldspar, lithic fragments, clay minerals, and mica.

What does lithic fragments mean?

Pieces of other rocks that have been eroded down to sand size. Signup and view all the answers

How are clastic sedimentary rocks described and classified?

Based on dominant size of grains present. Signup and view all the answers

What grain size scale is primarily used for describing clastic sedimentary rocks?

The Udden-Wentworth grain size scale. Signup and view all the answers

What are the three grain size factions for unconsolidated sediment?

Gravel, sand, and mud. Signup and view all the answers

What size is gravel?

Greater than 2 mm diameter. Signup and view all the answers

What size is sand?

Between 0.0625 mm (1/16) and 2 mm diameter. Signup and view all the answers

What are the two types of mud?

Clay and silt. Signup and view all the answers

What size is clay?

Less than 1/256 mm. Signup and view all the answers

What size is silt?

Between 1/16 mm and 1/256 mm. Signup and view all the answers

What are conglomerates/breccias made of?

Mostly gravel. Signup and view all the answers

What are sandstones made of?

Mostly sand. Signup and view all the answers

What are mudstones/claystones mostly made of?

Mud/clay. Signup and view all the answers

What are conglomerates composed of?

Dominantly rounded gravel. Signup and view all the answers

What are breccias made of?

Dominantly angular gravel. Signup and view all the answers

What is the most common sandstone classification scheme?

Based on the relative abundance of quartz, feldspar, and lithic fragments. Signup and view all the answers

How do you determine the first word in a sandstone name?

Based on the relative abundance of sand-sized framework grains. Signup and view all the answers

Quartz sandstones have ___ quartz grains?

greater than 90% Signup and view all the answers

Feldspathic sandstones have _ quartz grains and more _ grains than ___ grains.

Less than 90%, feldspar, lithic Signup and view all the answers

Lithic sandstones have _ quartz grains and more _ grains than ___ grains.

Less than 90%, lithic, feldspar Signup and view all the answers

What is a clean sandstone?

A sandstone with open pore space. Signup and view all the answers

What are arenites?

Clean sandstones. Signup and view all the answers

What are wackes?

Muddy sandstones with abundant muddy matrix (greater than 10% muddy matrix). Signup and view all the answers

What are mudstones?

Sedimentary rocks composed of at least 50% silt and clay sized particles. Signup and view all the answers

Siltstones are mainly composed of _ and with grain size from _ to ___.

Silt, 1/256 mm to 1/16 mm Signup and view all the answers

Mudstones are mainly composed of ___.

Equal mixture of silt and clay sized particles. Signup and view all the answers

Claystones are mainly composed of _ and with grain size less than _.

Clay, 1/256 mm Signup and view all the answers

What is detritus?

Solid materials that are weathered/eroded off the parent rock. Signup and view all the answers

What are the most common minerals found in detrital rocks?

Clay minerals and quartz. Signup and view all the answers

How are detrital sedimentary rocks classified?

Based on the grain size present. Signup and view all the answers

How are chemical sedimentary rocks formed?

Precipitate out of solution. Signup and view all the answers

Precipitation in chemical rocks is driven by _ and _.

Evaporation and saturation. Signup and view all the answers

Are chemical sedimentary rocks organic or inorganic?

False Signup and view all the answers

What are some common types of chemical sedimentary rocks?

Halite, sylvite, and gypsum. Signup and view all the answers

How are chemical sedimentary rocks classified?

Based on composition (not texture), but texture is used in naming once constituents are identified. Signup and view all the answers

How are biochemical sedimentary rocks created?

When... Signup and view all the answers

Study Notes

Sedimentary Rocks Overview

Four types: Clastic, biochemical (biogenic), chemical, and other.

Clastic Sedimentary Rocks

Composed of silicate minerals and rock fragments transported and deposited.
Typical components: quartz, feldspar, lithic fragments, clay minerals, and mica.
Described and classified by dominant grain size.
Udeen-Wentworth grain size scale is commonly used.

Grain Size Classification

Three factions for unconsolidated sediment: gravel, sand, and mud.
Gravel: greater than 2mm diameter.
Sand: between 0.0625 mm (1/16) and 2 mm diameter.
Mud: composed of clay and silt.
Clay: less than 1/256 mm; Silt: between 1/16 mm and 1/256 mm.

Types of Clastic Rock

Conglomerates/breccias: mostly gravel, where conglomerates are rounded and breccias are angular.
Sandstones: primarily sand.
Mudstones/claystones: composed of mud/clay.

Sandstone Classification

Most common classification scheme focuses on relative abundance of quartz, feldspar, and lithic fragments.
First word in sandstone name determined by the relative abundance of sand-sized framework grains.
Quartz sandstones: greater than 90% quartz grains.
Feldspathic sandstones: less than 90% quartz, more feldspar than lithic grains.
Lithic sandstones: less than 90% quartz, more lithic than feldspar grains.

Characteristics of Sandstones

Clean sandstone: has open pore space, also known as arenites.
Wackes: muddy sandstones with greater than 10% muddy matrix.

Mudstones and Siltstones

Mudstones: at least 50% silt and clay-sized particles, equal mixture of both.
Siltstones: mainly silt, with grain size from 1/256 mm to 1/16 mm.
Claystones: predominantly clay particles, with grain size less than 1/256 mm.

Detrital Sedimentary Rocks

Detritus: solid materials weathered/eroded from parent rock.
Common minerals in detrital rocks: clay minerals and quartz.
Classified based on grain size present.

Chemical Sedimentary Rocks

Formed by precipitation out of solution driven by evaporation and saturation.
Inorganic; no organic means involved.
Common types include halite, sylvite, and gypsum.
Classified based on composition, but texture may be used once mineral and chemical constituents are identified.

Biochemical Sedimentary Rocks

Created through biological processes (details not fully provided).

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Description

Test your knowledge on the classification and physical properties of sedimentary rocks with these flashcards. Covering types such as clastic and biochemical, this quiz will help reinforce your understanding of their composition and characteristics.