sedimentarsedimentary rocksy rocks

A. Formation:A. Formation:1. Sedimentary rocks form from the COMPACTION & COMPACTION & CEMENTATIONCEMENTATION of rock fragments/sediments2. Lithification: the changing of sediments into sedimentary rock

3. Sedimentary rocks are similar to the sediments from which they form (ie. Sandstone is made up of sand)

B. CLASTICB. CLASTIC1. Form when rock fragments & sediment are carried & deposited by GRAVITY, WIND, GLACIERS, & RUNNING WATERRUNNING WATER

Clastic Rock Formation

Most sediment is carried byMost sediment is carried byRunning WaterRunning Water

2. The further water carries sediment, the ROUNDER & ROUNDER & SMOOTHERSMOOTHER the sediment becomes3. When a stream slows down, it drops the LARGESTLARGEST particles first, & the SMALLESTSMALLEST last (HORIZONTAL SORTING)(HORIZONTAL SORTING)

Observe how sediments are deposited

So….

• If you are far out from shore, would you expect the grain size of the rocks to be large or small?

• What about if you are close to the shore?

That means….

4. Rocks formed closer to shore will be made up of bigger fragments than rocks formed farther away from the shore

BrecciaBreccia – very large sediments that are angular,

most likely deposited by gravity

ConglomerateConglomerate – large

sediments that are rounded (have been

transported by a stream!)

C. CRYSTALLINEC. CRYSTALLINE

1. Formed when dissolved minerals in seawater are deposited (seawater evaporates,seawater evaporates, leaving the minerals behind to crystalize)2. Also known as CHEMICAL

Salt “Mines”Salt “Mines” - Rock Salt is being formed as the salt water evaporates

from the sea.

““Devil’s Golf Devil’s Golf Course”Course” – millions of years ago this was a sea of salt water. It has been

evaporating over time…

…and has formed

“pockets” of chemical

limestone, rock salt, and rock gypsum!

D. BIOCLASTICD. BIOCLASTIC

1. Formed from the remains of plants & animals that are compacted

– Fossil LimestoneFossil Limestone – formed when shell remains of marine organisms are cemented in fragments•Shells are made of CALCITE which reacts with acid

2. Coal Formation

a. Long ago, huge trees grew in the warm, humid

swamps.

b. Trees died and decomposed into what is

called PEAT

c. Peat was buried under layers of mud.

d. Pressure increased, slowly changing the plant

remains into coal.

Coal – Coal – note note

distinct distinct layering layering of peatof peat

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STRATIFICATIONSTRATIFICATION

1. STRATIFICATION1. STRATIFICATION (layering): Layers of sediments that have SIMILARLYSIMILARLY colored minerals and are typically sandstones or siltstones

2. Fossils2. Fossils – actual remains, imprints from plants or animals, or preserved traces from living things

bells & whistles for bells & whistles for sedimentary rock sedimentary rock

identification!identification!• Stratification• Fossils• Fragments of

materials cemented together

• Ripple marks• Mud cracks

Angel’s Landing, Zion Angel’s Landing, Zion Nat’l Park, UtahNat’l Park, Utah – note

rock layers

Red Sandstone, UtahRed Sandstone, Utah – note distinct LAYERING of sediments (sand)

Horseshoe Bend, Utah

Grand Canyon Nat’l Park, ArizonaGrand Canyon Nat’l Park, Arizona – sedimentary rock formation at its best! The canyons were formed by the Colorado River

cutting into the rock layers over time!

Fossils

•The remains, impression or any other evidence of a plant or animal preserved in rock.

• Fossilization

Brachiopod fossils in limestone Imprint

of a leaf

Trilobite fossils – over 250 MILLION years old!!!

Mud Cracks and Ripples

• Ripple Marks: A sand pattern formed by the action of winds, streams, waves or currents; preserved when sand becomes sandstone

• Mud Cracks: Develop when deposits of wet clay dry and contract. The cracks are filled with sediments and fossilize when the clay becomes shale

Ripple Marks in the Shale from

running water as the

rock was forming