SEDIMENTARY ROCKS

Sediment

Loose, solid particles that can originate by:

1. Weathering and erosion of preexisting rocks

2. Chemical precipitation from soultion (usually in water)

3. Secretion of organisms

Fossils

Traces of plants or animals preserved in rocks.

Detrital Sediment

Sediments made up of mineral grains or parts of other rocks - inorganic.

Chemical Sediment

Sediments that precipitate from solution or remians of biologic organisms - biochemical.

Inorganic

Materials not derived from living organisms, typically consisting of minerals and non-biological components - solid particles.

Mechanical Weathering

The process of breaking down rocks into smaller pieces without changing their chemical composition, typically through physical forces such as temperature changes, freezing, and thawing.

Chemical Weathering

The process of breaking down rocks through chemical reactions, leading to the alteration of their mineral composition, often involving water and atmospheric gases.

Basins

Deposition centers for sedimentary materials, often forming lake beds or ocean floors.

Lithification

The process of producing sedimentary rocks through compaction and cementation of sediments. Loose sediments are transformed into solid rock.

Compaction

A loss in overall volume and pore space of a rock as the particles are packed closer together by the weight of overlying material.

Cementation

The chemical precipitation of material in the spaces between sediment grains, binding the grains together into a hard rock.

Grain Size

An indicator of the distance from the source area.

Grain Rounding

Another indicator of distance from source area.

Grain Sorting

Gives clues to the distance from the source area and energy of the environment.

(the farther you move away from source area, the more sorted materials will be)

Chemical Sediment

Sediment formed through precipitated materials that were once in solution. Can be classified as inorganic or organic, depending on the source of the material. Either precipitated from physical processes or life processes (biochemical origin).

Precipitated

Material that has solidified from solution.

Biochemical Sediment

Sediment formed from the remains of living organisms, resulting in the accumulation of materials like shells or plant debris.

Evaporites

Chemical sediments formed from the evaporation of water, leaving behind minerals such as rock salt and gypsum.

Strata

Layers of sedimentary rock that are the most characteristic. Also known as beds - used like pages in a book. They record the geological history and changes in the environment over time.

Bedding Planes

The surfaces that separate different strata, indicating periods of non-deposition or erosion in sedimentary rock formations.

Facies

Distinctive characteristics of sedimentary rocks that indicate environment of deposition, such as grain size, composition, and fossil content.

Sedimentary Structures

A feature found within sedimentary rocks, usually formed during or shortly after deposition of the sediment and before lithification.

➢ What are sediments?

Small particles of rock, mineral grains, or organic material that accumulate over time through weathering and erosion.

➢ Why are sedimentary rocks important?

They are used to reconstruct much of Earth’s history, give clues about past environments, and provide information about sediment transport.

➢ Two main types of sediments:

Detrital & Chemical

➢ How are detrital sediments classified?

Classified by particle size.

➢ What are the main transport mechanisms of sediment and their capacities?

Wind transport: small grains - sand sized or smaller.

Water transport: variety of sizes depending on energy of the stream or waves - respondsible for most sedimentary deposits.

Ice transport: widest range of particle sizes.

➢ Types of sediment loads:

Bed load: material slides, rolls, or bounces along the ground surface or river bottom.

Suspended load: fine grained material is carried in the air or water column.

Dissolved load: ions and chemicals dissolved in water.

➢ Process of lithification:

Loose sediments are transformed into solid rock through compaction and cementation.

➢ Size, Sorting, and Rounding and what information they convey:

All characterisitcs of sedimentary rocks. Size and rounding are indicators of the distance from source material. Sorting gives clues to the distance from source area and energy of the environment.

➢ Types of Chemical Sedimentary rocks:

• Limestone (most abundant chemical rock)

• Evaporites: rock salt & gypsum

• Microcrystalline quartz

• Coal

➢ Chemical vs. Biochemical sediments:

Chemical sediments form directly from precipitated solutions, while biochemical sediments result from the activity of organisms.

➢ Coal formation and evaporites:

Coal forms in fresh water swamps when the plants produce more litter and the decomposers cannot keep up. Evaporites form through the evaporation of water, which leads to the precipitation of minerals like rock salt and gypsum.

➢ Features unique to sedimentary rocks:

Strata (beds), Bedding planes, and fossils.

➢ Why do sedimentary layers end?

Due to environment limits and deposition.

➢ Sedimentary structures and their importance:

Ripple Marks, Crossbreeding, Mudcracks, and Graded Bedding. The importance of these structures lies in their ability to provide insight on pas environments, climates, events, ancient life, and sequence of events.