Sedimentary Rocks

Sedimentary Rocks

• Related word = “sediment”

• Sediment - pieces of solid material that have been deposited on earth’s surface by water, wind, ice, gravity or chemical precipitation

Sedimentary Rocks

• Related word = “sediment”

• Sediment - pieces of solid material that have been deposited on earth’s surface by water, wind, ice, gravity or chemical precipitation

Weathering

• a set of physical and chemical processes that break rock into smaller pieces

• Chemical weathering -• When minerals in a rock are dissolved

and the rock is changed chemically• Physical weathering -

• Minerals remain unchanged• Simply break into small pieces

Clastic Sediments

• Produced by weathering

What is Sand?

Erosion and Transport• The removal and movement of surface

materials from one location to another

• Carried by wind, water, ice and gravity

• Materials usually move downhill

Erosion and Transport

Deposition• When materials are laid down on the ground or

sink to the bottom of bodies of water

• When transport stops, materials are deposited

• Generally, largest particles settle out first and produce sorted layers

• Glacier and landslide deposits not sorted

Burial• When materials are deposited in basins, other

sediments are deposited on top if them.

• This leads to the layered appearance that some sedimentary rocks exhibit

Lithification• Litho?

Lithification• Litho?

• Lithification - the physical and chemical processes that transform sediments into sedimentary rocks

Compaction Cementation Lithification

Lithification• Compaction? (Similar words?)

• Compaction - clasts (?) are squeezed together. Water is squeezed out.

Lithification• Cementation? (Similar words?)

• Cementation - mineral growth in spaces between clasts cements clasts together

• Two methods:

Features of Sedimentary Rocks

• Bedding - visible horizontal layers in the rock

• Beds can be millimeters thick or meters thick

• Type of bedding depends upon the method of

transport.

• Size of grains depend on many factors

Graded Bedding

• Particle size is bigger and coarser at the bottom of the beds

• Underwater landslides, fast-moving streams

Cross-Bedding

• Formed as inclined layers of sediment move forward across a horizontal surface

• Sand dunes, beaches, lake edges

Cross-Bedding

• Formed as inclined layers of sediment move forward across a horizontal surface

• Sand dunes, beaches, lake edges

Evidence of Past Life• Fossils - preserved remains, impressions or

any other evidence of once-living organisms (Why not in igneous?)

Fossils and Sedimentary Rocks

• Fossils can help ID the rocks, and vice-versa!

• Types of fossils found give a clue about the rock’s origin- fossils of marine animals indicate ……

Fossils and Sedimentary Rocks• Fossils can help ID the rocks, and vice-versa!

• Types of fossils found give a clue about the rock’s origin- fossils of marine animals indicate ……

The rock formed from sediments deposited near (or in) the sea.

Classifying Sedimentary Rocks

Classifying Sedimentary Rocks

Clastic Sedimentary Rocks• Coarse-Grained Clastics

Conglomerate Breccia

Clastic Sedimentary Rocks

Grain Shape - Influenced by:

• Distance of transport - The further it travels, the rounder it becomes

• Length of time of transport- The longer it’s affected by water, wind or ice, the rounder it becomes

Clastic Sedimentary Rocks• Medium-Grained Clastics - (Sandstone)

sometimes contain oil, natural gas and groundwater

• Porosity: percentage of open space between grains

Clastic Sedimentary Rocks• Fine-grained Clastics (Shale)

• Has low porosity that hinders movement of oil, water and natural gas

Classifying Sedimentary Rocks

Chemical Sedimentary Rocks• Formed from the evaporation of saturated

liquids

• Called evaporites

Chemical Sedimentary Rocks

Classifying Sedimentary Rocks

Organic Sedimentary Rocks

Biogenic - (bio = ?; genic = ?)

Organic Sedimentary Rocks

Biogenic - (bio = ?; genic = ?) Formed from the remains of once-living

things - limestone Organisms use calcium carbonate in their

shells and skeletons When they die, they sink to the bottom. Calcium carbonate precipitates into the water

the cements the grains of carbonate sediment.

Organic Sedimentary Rocks

Organic Sedimentary Rocks

Biogenic - (bio = ?; genic = ?) Formed from the remains of once-living

plants - coal Plants in swamps and coastal areas die are

buried and compressed. Lithified into coal Why is it called a Fossil fuel?

Identifying Sedimentary Rocks

Identifying Sedimentary Rocks

Identifying Sedimentary Rocks

Identifying Sedimentary Rocks