Lecture 9A: Sedimentary Rocks and Processes

Sedimentary Rock

Classified rock composed of sediments that undergo lithification by compaction and cementation.

Sediments

Material derived from the weathering and erosion of rocks, including detrital and biochemical sediments.

Detrital Sediments

Sediments formed from rock and mineral fragments.

Biochemical Sediments

Sediments composed of biological material, such as shells and plant material.

Clastic Rocks

Rocks composed of detrital sediments.

Mudstone

A type of clastic rock made of clay-sized particles that do not break into planes.

Shale

A clastic rock that breaks into planes due to its clay-sized particle composition.

Sandstone

A type of clastic rock made of sand that exhibits lamination or bedding.

Conglomerate

A clastic rock composed of rounded clasts.

Breccia

A clastic rock composed of angular clasts.

Coquina

A biochemical rock predominantly made of shells.

Fossiliferous Limestone

A limestone rock that contains abundant fossils.

Chert

A biochemical rock made of radiolarians found in deep marine environments.

Diatomites

A biochemical rock composed of diatoms, either pennate or centric.

Chalk

A biochemical rock made of coccolithophores.

Chemical Sedimentary Rock

Rocks formed from minerals precipitating from a solution.

Speleothems

Cave precipitates such as stalactites and stalagmites.

Travertine

A type of terrestrial limestone formed from mineral precipitation.

Sedimentary Process

Processes that shape sedimentary rocks from their source to their formation.

Weathering

The breakdown of rock material into smaller fragments.

Physical Weathering

The mechanical breakdown of rocks without changing their chemical composition.

Chemical Weathering

The breakdown of rocks that involves changes in their chemical composition.

Differential Weathering

The process where different rock materials weather at different rates.

Disintegration

The breakdown of larger rock bodies into smaller units through physical weathering.

Frost Wedging

A form of physical weathering caused by the expansion of freezing water.

Abrasion

Mechanical wearing down of rock surfaces by friction.

Dissolution

A process in chemical weathering where minerals are wholly or partly dissolved.

Carbonation

A chemical reaction where carbonic acid reacts with minerals like calcite.

Hydrolysis

A chemical reaction between minerals and water forming new minerals.

Oxidation

A chemical reaction involving the loss of electrons from a mineral, increasing its oxidation state.

Soil

A product of weathering capable of supporting rooted plants.

Erosion

Action of processes that wear away and transport rock particles and ions from the source.

Transportation

The movement of sediments from their source to depositional sites.

Diagenesis

Processes resulting in the transformation of sediments into sedimentary rock.

L lithification

The process of compaction and cementation that converts sediments into sedimentary rock.

Grain Size

Measurement of the size of individual particles in sedimentary rocks.

Sorting

The uniformity of grain sizes in a sediment sample.

Bedding

Layers of sedimentary rock that indicate the environment of deposition.

Cross-bedding

Sedimentary structures formed by the intersection of layers at an angle.

Bioturbation

The disturbance of sediments by burrowing organisms.

Importance of Sedimentary Rocks

They serve as a record of geological history, host resources, and a biological record.

Udden-Wentworth Scale

Scale used to classify the grain size of sedimentary rocks.

Goldich Stability Series

Method for predicting the stability or weathering potential of minerals.

Karst Environment

Landforms associated with the dissolution of soluble rocks, often featuring sinkholes.

Chelation

Organic process where soluble molecules bind with metallic elements to remove them from minerals.

Talus

Debris deposits that accumulate at the foot of slopes.

Hjulström Curve

Graph illustrating the relationship between particle size and river velocity regarding erosion and deposition.