structures of sedimentary rocks

STRUCTURES OF STRUCTURES OF SEDIMENTARY SEDIMENTARY

ROCKSROCKS

M.RAJASEKHAR ASST. PROFESSOR KUPPAM ENGINEERING COLLGE

Structures of Structures of sedimentary rocks formed by the deposition of sediments or sedimentary rocks formed by the deposition of sediments or fragments by the process of ETDfragments by the process of ETD

Sedimentary structures are classified into different types based upon the Sedimentary structures are classified into different types based upon the deposition of sediments they aredeposition of sediments they are

1. Stratification2. Graded bedding3. Cross bedding4. Ripple marks5. Mud cracks6. Rain drop marks7. Cast and mould8. Tool marks 9. Track and Trails10.Burrow marks

StratificationStratificationStratum- bed Strata- Series of beds Stratification is defined as the deposition of sediments or fragments in the series of beds. These beds having different in mineralogy, clast size, degree of sorting and color of the different layers. Thickness of beds are very less is called “Lamination”

Graded BeddingGraded Bedding The velocity of the transporting agent decrease the larger or more dense particles are deposited first, followed by similar particles The bedding showing a decrease in grain size from the bottom of the bed to the top of the bed.

Cross BeddingCross Bedding Consists of set of beds that are inclined relative to one another. The beds are inclined in the direction that the wind or water was moving at the time of deposition. Crass bedding very common in beach deposits, sand dunes, river deposits.

SEDIMENTSEDIMENT TransportationTransportation

AbrasionAbrasion RoundingRounding SortingSorting DepositionDeposition

Environment of deposition- specificEnvironment of deposition- specific PreservationPreservation

Ripple marksRipple marks Caused by waves or winds moves up the sediment into long ridges.

→Ripple marks are shallow water deposition→Asymmetrical ripple marks can give an indication of current direction→Symmetrical ripple marks form when the waves moves back and forth

Mud CracksMud Cracks Cracks on the sediment are developed due to the shrinkage of the sediment as it dries. ORFormed as muddy sediment dries and contracts.Formed as muddy sediment dries and contracts.

Crack formation also occurs in clayey soils as a result Crack formation also occurs in clayey soils as a result of a reduction in water content. of a reduction in water content.

Cast and MoldsCast and MoldsAny depression formed on the bottom of a body of water may become a mold, later get deposited into the depression and will acquire the shape of that depression called cast.

The body of sediment that gets the shape of the mold is cast.

Tool MarksScratch marks on the bottom of the water resulting due to any object carried along by currents are called tool marks.

Rain prints or rain drop points

Pits created by falling rain

Tracks and TrailsThese features are formed when organisms move across the sediment as they walk, crawl or drag their body parts through the sediment.

Burrow marksBurrow marksFormed by any organism that burrows into sediment.

CHEMICAL CHEMICAL SEDIMENTARY ROCKSSEDIMENTARY ROCKS

Carbonate RocksCarbonate Rocks Limestone- made of calciteLimestone- made of calcite

Inorganic varietiesInorganic varieties micrite, oolites, travertinemicrite, oolites, travertine

DolomiteDolomite RecrystallizationRecrystallization

Chert- silicaChert- silica EvaporitesEvaporites

Rock gypsumRock gypsum Rock saltRock salt

BIOCHEMICAL BIOCHEMICAL SEDIMENTARY ROCKSSEDIMENTARY ROCKS

CoalCoal Develops from peatDevelops from peat

plant fragmentsplant fragments LigniteLignite Bituminous CoalBituminous Coal

Carbonate RocksCarbonate Rocks Limestone- made of calciteLimestone- made of calcite

organic varietiesorganic varieties CoquinaCoquina Fossiliferous LimestoneFossiliferous Limestone ChalkChalk

SEDIMENTARY SEDIMENTARY STRUCTURESSTRUCTURES

BEDDING-BEDDING- Principle of Original HorizontalityPrinciple of Original Horizontality Bedding planeBedding plane Cross-beddingCross-bedding Graded bedGraded bed Mud cracksMud cracks Ripple marksRipple marks FossilsFossils

DUNESDUNES

MudcracksMudcracks



Body FossilsBody Fossils Trace FossilsTrace Fossils

Glacial Environment & Glacial Environment & TillTill

CALCAREOUS

structures of sedimentary rocks

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