Sedimentary Rocks Created By: Mr. Kreeger

Homework and Page References Page References HW # 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 Contents 1. Sediments 2.Sedimentary Rocks Defined 3.Formation of Sedimentary Rocks 4.3 Types of Sedimentary Rocks a. Clastic Grain Size Grain Shape Grain Arrangement b.Chemical c.Organic 5.How to Classify Sedimentary Rocks

Introduction to Sedimentary Rocks

1. Sediments These are loose grains and chemical residues of Earth materials –Formed by: Chemical and Physical weathering

2. 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 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 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 RUNNING WATERFormed when rock fragments & sediment are carried & deposited by WIND, GLACIERS, & RUNNING WATER DEPOSITED COMPACTED CEMENTEDSediments are DEPOSITED, then COMPACTED & finally CEMENTED together

4a1. Grain Sizes of Clastic 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 Grain Size Grain SizeSedimentRock name Larger than 2mmGravelConglomerate 2mm to 0.06mmSandSandstone 0.06 to 0.002mmSiltSiltstone Smaller than 0.002mmClayShale

4a2. Grain Shape of Clastic Sedimentary Rocks Grain Shape- Sediments can be transported over a great distance by wind water and ice. 1.Angular- Transported short distance 2.Rounded- Traveled longer distance 3.Well Rounded- Traveled very long distance. Well Rounded Angular

4a3. Grain Arrangement of Clastic Sedimentary Rocks Grain Arrangements- Different velocities of wind and water currents capable of transporting and separating different densities and sizes of sediments 1.Poorly Sorted- Many different sizes 2.Well Sorted- All grains same size Poorly Sorted Well Sorted

Stream Velocity versus Particle Size

4b. CHEMICAL seawater evaporates,Formed when dissolved minerals in seawater are deposited (seawater evaporates, leaving the minerals behind) Usually old swamps, seas, or lakes evaporate CRYSTALLINEAlso known as CRYSTALLINE 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 Course” “Devil’s Golf 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 Limestone –Fossil 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 swamp is buried & compressed, coal may form Coal – note distinct layering of peat

5. How to Classify Sedimentary Rocks 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

Don’t forget: You can copy- paste this slide into other presentations, and move or resize the poll. Poll: Which rock was organically formed and...

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