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Chapter Six. Sediments & Sedimentary Rocks. Sediment. Sediment - loose, solid particles originating from: Weathering and erosion of pre-existing rocks Chemical precipitation from solution, including secretion by organisms in water Classified by particle size Boulder - >256 mm

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Chapter Six

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Chapter six

Chapter Six

Sediments & Sedimentary Rocks


Chapter six

Sediment

  • Sediment - loose, solid particles originating from:

    • Weathering and erosion of pre-existing rocks

    • Chemical precipitation from solution, including secretion by organisms in water

  • Classified by particle size

    • Boulder - >256 mm

    • Cobble - 64 to 256 mm

    • Pebble - 2 to 64 mm

    • Sand - 1/16 to 2 mm

    • Silt - 1/256 to 1/16 mm

    • Clay - <1/256 mm


Sedimentation and sedimentary rocks

SEDIMENTATION AND SEDIMENTARY ROCKS

  • INTRODUCTION

    IMPORTANCE OF SEDIMENTARY ROCKS:

    i) 75% OF ROCKS EXPOSED AT THE EARTH’S SURFACE

    ii) SOURCE OF FOSSIL FUELS, IRON AND ALUMINUM

    ORES, ALUMINUM ORES, AND GROUNDWATER

    iii) RECORD OF EARTH’S HISTORY


Types of sediment

TYPES OFSEDIMENT


Ii origin of sedimentary rocks

II ORIGIN OF SEDIMENTARY ROCKS:

A. INTRODUCTION

1. REVIEW OF WEATHERING PROCESSES:

2. CLASSIFICATION OF SEDIMENTS

a) DETRITAL SEDIMENT: PREEXISTING FRAGMENTS OF PREEXISTING IGNEOUS, SEDIMENTARY AND METAMORPHIC ROCKS

  b) CHEMICAL SEDIMENT: PRECIPITATED FROM WATER OR EXTRACTED BY ORGANISMS AND DEPOSITED LATER

B. SEDIMENT TRANSPORT AND TEXTURE

1. INTRODUCTION

i) TRANSPORTATION AND DEPOSITION OF CHEMICAL

SEDIMENTS

ii) TRANSPORTATION AND DEPOSITION OF DETRITAL

SEDIMENTS


2 grain size controlled by

2. GRAIN SIZE – CONTROLLED BY:

a) NATURE OF PARENT ROCKS

b) NATURE AND ENERGY LEVEL OF TRANSPORT MEDIUM

1) SORTING

·        WELL-SORTED: WIND MOST SELECTIVE

POORLY-SORTED: GLACIERS AND FLOODING RIVERS SORT

POORLY

2) CURRENT VELOCITY


Grain size

Grain size

  • 3) GRAIN SHAPE - DEPENDS ON:

  • a) TRANSPORT MEDIA: SWIFTLY FLOWING RIVERS BOUNCE PEBBLES

  • AND SAND GRAINS AROUND VIGOROUSLY

  • b) DISTANCE FROM PARENT ROCK (AT THE BASE IF A GLACIER MAY

  • BE GROUND TO A ROCKY POWDER)

  • c)MINERAL HARDNESS:


Sediment in a stream

Sediment in a Stream


C sedimentary structures

C. SEDIMENTARY STRUCTURES:

1. BEDDING (STRATIFICATION): ARRANGMENT OF SEDIMENT

PARTICLES INTO DISTINCT LAYERS

a) CHANGES IN SEDIMENT:

b) CHANGES IN TRANSPORT ENERGY

2. GRADED BEDDINGS:SEDIMENT LAYER (FORMED BY A SINGLE

DEPOSITONAL EVENT) IN WHICH PARTICLE SIZE VARIES

GRADUALLY WITH THE COARSEST PARTICLES ON THE BOTTOM


Development of a bedding plane

Development of a bedding plane


Develop bedding plane contd

Develop. Bedding plane-contd.


Develop bedding plane contd1

Develop. Bedding plane contd.


Graded bedding of sediment

Graded bedding of sediment


Development of cross bedding

Development of cross-bedding


Cementation recrystallization

Cementation & Recrystallization

  • 4.CEMENTATION: PRECIPITATION OF DISSOLVED IONS IN THE PORE

  • SPACE

  • a) CALCIUM CARBONATE

  • b) SILICA

  • c) IRON COMPOUNDS

  • 5.CLASTIC TEXTURE: FORMED BY COMPACTION AND CEMENTATION OF

  • SEDIMENT PARTICLES HAS CLASTIC TEXTURE

  • 6.RECRYSTALLIZATION: RECRYSTALLIZATION OF CERTAIN UNSTABLE

  • MINERALS INTO NEW, MORE STABLE MINERALS


Iii classication of sedimentary rocks

III. CLASSICATION OF SEDIMENTARY ROCKS:

DETRITAL SEDIMENTARY ROCKS:

  • MUDSTONES

  • SANDSTONES

  • CONGLOMERATES

  • BRECCIAS

    A. DETRITAL SEDIMENTARY ROCKS:

    1. INTRODUCTION: CLASSIFICATION BASED ON

    PARTICLE SIZE

    a) ALL DETRITAL ROCKS ARE CLASTIC

    b) SAND AND SILT PREDOMINANTLY QUARTZ

    c) FINER-SIZED PARTICLES OF CLAY MINERALS


Chapter six

2. MUDSTONES

a) MORE THAN HALF OF ALL SEDIMENTARY ROCKS

b) CONTAIN THE SMALLEST PARTICLES (0.004 mm IN DIAMETER)

c) ENVIRONMENTS OF DEPOSITION: LAKES, LAGOONS, DEEP OCEAN

BASINS, RIVER FLOODPLAINS

d) COLOR VARIETY OF SHALE REPRESENTS MINERAL COMPOSITION

e) PRACTICAL USES OF SHALE: BRICKS, CERAMICS, CEMENT, AND OIL

SHALE


Chapter six

3.SANDSTONES:

a) 25% OF ALL SEDIMENTARY ROCKS

b) SANDSTONE PARTICLES (1/16-2 MM IN DIAMETER)

c) PRACTICAL USES OF SANDSTONES: BUILDINGS AND RESERVOIR

FOR FOSSIL FUELS AND GROUNDWATER

4.CONGLOMERATES AND BRECCIAS

a) GRAINS LARGER THAN 2 MM

b) CONGLOMERATES HAVE ROUNDED GRAINS

c) BRECCIAS HAVE ANGULAR GRAINS


B chemical sedimentary rocks

B. CHEMICAL SEDIMENTARY ROCKS

INORGANIC CHEMICAL SEDIMENTARY ROCKS

a) LIMESTONE (INORGANIC)

i) FORMATION

ii) OOLITIC LIMESTONE

iii) TUFA

iv) TRAVERTINE


Cross bedding mudcracks

Cross-bedding & mudcracks

3. CROSS-BEDDING: SEDIMENTARY LAYERS DEPOSITED AT AN

ANGLE TO THE UNDERLYING SET OF BEDS

4. SURFACE SEDIMENTARY FEATURES

a) RIPPLE MARKS: SMALL SURFACE RIDGES PRODUCED WHEN

WATER OR WIND FLOWS OVER SEDIMENT AFTER IT IS

DEPOSITED

b) MUDCRACKS:OCCUR ON THE TOP OF A SEDIMENT LAYER

WHEN MUDDY SEDIMENT DRIES AND CONTRACTS


Origin of mud cracks

Origin of mud cracks


Asymmetric and symmetric ripples

Asymmetric and symmetric ripples


D lithification turning sediment into sedimentary rock

D. LITHIFICATION: TURNING SEDIMENT INTO SEDIMENTARY ROCK

  • 1. DEFINITION OF DIAGENESIS: CHANGES IN THE SEDIMENT DUE TO INCRESED HEAT, PRESSURE, AND CIRCULATING GROUNDWATER

  • 2. DEFINITION OF LITHIFICATION: END RESULT OF DIAGENESIS

  • 3. COMPACTION: DIAGENETIC PROCESS BY WHICH THE WEIGHT OF OVERLYING MATERIALS REDUCES THE VOLUME OF SEDIMENTARY BODY


Lithification of sediment

Lithification of sediment


Initial deposits of flat tabular clay

Initial deposits of flat/tabular clay


Formation of ooliths

Formation of ooliths


Locations of subsurface evaporite

Locations of subsurface evaporite


Formation of coal from swamp deposits

Formation of coal from swamp deposits


Formation of coal contd

Formation of coal –contd.


Common geological environment

Common geological environment


Geology at a glance

Geology at a glance


Marine sedimentary environment

Marine sedimentary environment


Sedimentary facies formation

Sedimentary facies formation


Sedi facies formation contd

Sedi. Facies formation – contd.


Landword migration

Landword Migration


Chapter summary

Chapter Summary

  • % of sedimentary rocks in outer 10 miles

  • Basic classification of sedimentary rocks

  • Most sedi. Rocks – Chemical or detrital

  • Definition of sedimentary rocks

  • Sorting by wind, glaciers (well sorted vs poor sorting)

  • Degree of sedimentary particle rounding

  • Bedding plane, sedimentary structure, occurrence

  • Diagenesis, Lithification, Cementation

  • Composition of detrital sedimentary rocks

  • Environment – deposition of shale

  • Breccia and Conglomerate

  • Oolitic Limestone

  • Definition of Sedimentary Facies – Characteristics that distinguish one from another


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