Sedimentary RocksSedimentary Rocks

Created By:Created By:

Mr. KreegerMr. Kreeger

Homework and Page References Homework and Page References

• Page References- 69-74

• HW # 1- 9-18 on page 75

• HW # 2- In a 2-3 paragraphs explain what stratification, ripple marks, mud cracks, fossils and concretions are and how they relate to sedimentary rocks.

Table of ContentsTable of Contents

1. Sediments2. Sedimentary Rocks Defined3. Formation of Sedimentary Rocks4. 3 Types of Sedimentary Rocks

a. Clastic• Grain Size• Grain Shape• Grain Arrangement

b. Chemicalc. Organic

5. How to Classify Sedimentary Rocks

Introduction to Sedimentary RocksIntroduction to Sedimentary Rocks

1. Sediments1. Sediments

• These are loose grains and chemical residues of Earth materials– Formed by:

• Chemical and Physical weathering

2. Sedimentary Rocks Defined2. Sedimentary Rocks Defined

• These are rocks that form when sediments are compressed together or otherwise hardened , or when masses of inter-grown mineral crystals precipitate from water.

3. Formation of Sedimentary Rocks3. Formation of Sedimentary Rocks

a. Lithification- The hardening of sediment to produce rock. Usually occurs in layers.

1. Compaction- Increased pressure from overlying sediment

2. Cementation- Binding together of sediments

3. Precipitation- When sea water evaporates leave aggregates of intergrown and interlocking crystals

Sedimentary Rock Identification Sedimentary Rock Identification Chart (Page 7 ESRT)Chart (Page 7 ESRT)

4. 3 types of sedimentary rocks

• CLASTICCLASTIC – formed from fragments of other rocks– Sandstone, Conglomerate

• CHEMICALCHEMICAL – formed from the mineral precipitates of evaporated seawater– Rock Salt

• ORGANICORGANIC – formed from the remains of plants & animals with rock fragments– Coal, Fossil Limestone

4a. CLASTIC

• Formed when rock fragments & sediment are carried & deposited by WIND, GLACIERS, & RUNNING WATERRUNNING WATER

• Sediments are DEPOSITEDDEPOSITED, then COMPACTEDCOMPACTED & finally CEMENTEDCEMENTED together

4a1. Grain Sizes of Clastic 4a1. Grain Sizes of Clastic Sedimentary Rocks Sedimentary Rocks

Based on Wentworth scale

Gravel- Grains >2mm (Boulders, pebbles)

Sand- Grains 1/16mm to 2mm (Sandbox)

Silt- 1/256mm to 1/16mm (too small to see)

Clay- <1/256mm (too small to see)

Pictures of Rocks With Specific Pictures of Rocks With Specific Grain SizeGrain Size

Grain Size Sediment Rock name

Larger than 2mm Gravel Conglomerate

2mm to 0.06mm Sand Sandstone

0.06 to 0.002mm Silt Siltstone

Smaller than 0.002mm Clay Shale

4a2. Grain Shape of Clastic 4a2. Grain Shape of Clastic Sedimentary RocksSedimentary Rocks

Grain Shape- Sediments can be transported over a great distance by wind water and ice.

1. Angular- Transported short distance2. Rounded- Traveled longer distance3. Well Rounded- Traveled very long distance.

Well Rounded----------------------------------------------------------Angular

4a3. Grain Arrangement of Clastic 4a3. Grain Arrangement of Clastic Sedimentary RocksSedimentary Rocks

Grain Arrangements- Different velocities of wind and water currents capable of transporting and separating

different densities and sizes of sediments1. Poorly Sorted- Many different sizes

2. Well Sorted- All grains same size

Poorly Sorted------------------------------------------------Well Sorted

Stream Velocity versus Particle Stream Velocity versus Particle SizeSize

4b. CHEMICAL

• Formed when dissolved minerals in seawater are deposited (seawater seawater evaporates,evaporates, leaving the minerals behind)

• Usually old swamps, seas, or lakes evaporate

• Also known as CRYSTALLINECRYSTALLINE because of the fine crystals – Limestone, Rock Salt, Rock Gypsum (sheetrock)

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!

4c. ORGANIC

• 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 and is a natural “cement”

Brachiopod fossils in limestone Imprint

of a leaf

Trilobite fossils – over 250 MILLION years old!!!

If peat at the bottom of a If peat at the bottom of a swamp is buried & swamp is buried &

compressed, coal may compressed, coal may formform Coal – Coal –

note note distinct distinct layering layering of peatof peat

5. How to Classify Sedimentary 5. How to Classify Sedimentary RocksRocks

1. Determine rocks general composition (Clastic, Organic or Chemical)

2. Describe rocks texture• Grain Size• Grain Shape• Grain Arrangement

3. Determine rocks name by using flow chart