Sedimentary Rx pages  For thousands, even millions of years, little pieces of our earth have been eroded-- broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.

Sedimentary rock is  Most common rock at Earth's surface  Thin blanket over 2/3 of the surface covering igneous and metamorphic rocks

FossilsFossils are often found in sedimentary rock. FossilsFossils are often found in sedimentary rock.  Ammonite  Fossil fish

Sedimentation  Volcanism builds new rocks  Weathering breaks them down into sediments

Two types of weathering: Mechanical and Chemical

Mechanical weathering Mechanical weathering breaks rock into smaller pieces Mechanical weathering Mechanical weathering breaks rock into smaller pieces Three ways Frost wedging Root wedging Gravity

Mechanical weathering Mechanical weathering increases the surface area of the rock exposed to chemical weathering Mechanical weathering Mechanical weathering increases the surface area of the rock exposed to chemical weathering

2. Chemical WeatheringChemical Weathering 2. Chemical WeatheringChemical Weathering Chemical Reactions with water dissolve rock H 2 O + CO 2 H 2 CO 3 Water and carbon dioxide yields carbonic acid This is what dissolves limestone and makes caves

Erosion  Erosion--movement of seds  What can move it ? (Agents of erosion) Wind Water Ice  The larger the sediment the harder it is to move

DepositionDeposition— seds are deposited DepositionDeposition— seds are deposited  When deposited sediment accumulates, it begins to transform into sedimentary rock

Two types of sedimentary rocks  Clastic Made of bits and pieces of recycled rock Chemical Form by precipitation or evaporization Called Precipitates and evaporites

Transformation Transformation of Clastic rocks occurs in two ways: Transformation Transformation of Clastic rocks occurs in two ways:  Compaction seds are pressed together – grains interconnect  Cementation Seds are cemented together like glue – Calcite, – silica, and – iron oxide are the most common cements.

Clastic sediments bits and pieces of old rock/plants/animals  Clastic sedimentary rocks are classified by their sediment size and shape Most common is shale--very fine particles Sandstone—sand sized particles Siltstone—silt size

Rounder seds mean longer transport

And by shape of seds Conglomerate- rounded seds

Breccia—angular seds

 Egyptian statue made from breccia

Chemical Sediments  Chemical sediments precipitate from water Two types – Carbonates – Evaporites

Carbonates Made of mostly calcite Ca CO 3 or CaMg CO 3  Limestone is CaCO 3 Very common here  Dolomite is CaMgCO 3 Some of the carbonate is replaced by magnesium

Evaporites  Evaporites evaporate from water when a basin dries up Gypsum CaSO 4. H 2 O Halite (Rock Salt) NaCl

Halite--—a salt playa

Sedimentary Rock Lab  Name the rocks you find in your sample bag.  Choices Sandstone Coal Conglomerate Coquina Gypsum Rock salt Oolitic limestone

Sed rock Sed rock review Sed rock Sed rock review  A sed rock quiz A sed rock quiz

Sedimentary environments  Sedimentary rocks provide information about events that occurred on Earth's surface  Their color, grain size, and composition give us information about what was happening when they formed

Sedimentary rock environmentsSedimentary rock environments

Crossbedding Crossbedding and Ripple Marks Crossbedding Crossbedding and Ripple Marks  Crossbedding gives us an indication of wind or water direction Crossbedding  Ripple marks may be Symmetrical-oscillating Asymmetrical- current ripple marks

CavesCaves form in sedimentary rock CavesCaves form in sedimentary rock

Depositional Environments  Delta -a fan-shaped body formed when water flows from a stream into a standing body of water  Example the Mississippi River Delta Mississippi River Delta The Nile River Delta

Environments  River—Alluvial  Desert--aeolian  Delta  Shoreline

Alluvial--River Channel  Unconsolidated gravels, sand, and clay

Alluvial Fan  Forms when sediment flows from a steep incline onto a flat floored valley and looses velocity rapidly  Seds are laid down the largest first, followed by progressively smaller and smaller as the velocity slows

Oxbow lake formation  An oxbow lake occurs between here and Oxford

Conglomerate- rounded seds Rounded seds indicate a longer distance of transport

Evaporites ---Gypsum Ca SO 4. H 2 O Halite (Rock Salt) NaCl

Gypsum

Sandstone would indicate a beach or desert was once there

Limestone

Sedimentary environment

What ancient environment would produce the following:

A REEF  a. A linear outcrop of fossiliferous limestone, massive bedding, many corals and algal structures

SAND DUNES  b: cross-bedded, well-sorted sandstone, with frosted quartz grains

c: Unsorted, unstratified, the angular boulders have scratches GLACIAL

A Glacial Moraine

d. Unsorted, unstratified, the the angular boulders don't have scratches. ALLUVIAL FAN

Name this structure

e: poorly sorted, but somewhat stratified sandstone and conglomerate with cut and fill structures. RIVER

f: very fine parallel bedding, diatoms, red clay, some thin graded bedding. DEEP OCEAN

g. Thick deposits rock salt and gypsum. RESTRICTED CONTINENTAL SEAS

Jurassic Seaway- example of a continental sea

h. Fine-grained sand (made of shell fragments) with ripple marks and worm burrows. LAGOON BEHIND REEF