MANUFACTURING PROCESS-II UNIT-1 THEORY OF METAL CUTTING
Sedimentary rocks
1.
2. The disintegrated products of pre existing rocks are formed by
water as sediments get deposited in suitable depression of the earth,
where it get consolidated and cemented to form sedimentary rock.
Sedimentary rocks are formed by consolidation and cementation of
sediments deposited under water
S e d i m e n t a r y R o c k s
4. Formation of sedimentary rocks
Sediment Transport and Deposition
Ice, water, and wind can all transport particles of various
sizes to another location
Weathered Sediment, transported by river
5. Conglomerates
Breccia
Sandstones
Shale/mudstones
TYPES OF SEDIMENTARY ROCKS
Clastic rocks
Evaporate rocks
These rocks are formed
due to evaporation of
saline water (sea water)
eg. Gypsum, Halite
(rock salt)
Carbonate rocks
Form basically from
CaCO3 – both by
chemical leaching
and by organic
source
(biochemical) eg.
Limestone; dolomite
Organic rocks
Form due to
decomposition of
organic remains
under
temperature and
pressure eg.
Coal/Lignite etc.
Chemical & Organic rocks
6. Weathering & erosion of pre-existing
rocks and minerals
Transportation by water, ice or wind
Deposition (Sediments is laid down)
Compaction
Cementation by silica or calcite
Recrystallization
Lithifaction
Digenesis Process
8. Particle size in sediments
Grade Grain Size Rock type
Pebble 10 mm & above
Gravel 2 mm to 10 mm
Sand 0.1 mm to 2 mm Sandstone
Silt 0.01 to 0.1 mm Silt stone
Clay Less than 0.01 Shale
Conglomerate
Conglomerate Sandstone Siltstone Shale
9. Non Clastic Sediments
1) Chemically formed Rocks 2) Organically formed Rocks
• Carbonate Rocks
• Salt Rocks
• Ferruginous Rocks
• Siliceous Rocks
Carbonate Rocks :
The most abundant carbonate rocks are Limestone and Dolomite , which are
formed by chemical precipitation of calcium carbonate from sea water.
Fossiliferous LimestoneLimestone Dolomite
10. Salt Rocks :
Evaporation is the major process involved in the
deposition of chemical precipitate. The salt deposits
formed by the evaporation of saline lakes are called
evaporites the principal mineral of these deposits are
chlorides and sulfates of Na, K, Mg & Ca. Example-
Gypsum & Anhydrite
Salt rock AnhydriteGypsum
11. Ferruginous Rocks :
These rocks are formed by chemical precipitation of iron oxide.
Such rocks contains a high proportion of iron bearing minerals
such as Siderite, Hematite & Pyrite.
Hematite
Siliceous Deposits:
These rocks are formed when silica is precipitated from water.
12. Organically formed Rocks
These rocks are composed mainly of remains of animals or plants.
1) Biochemical Rocks 2)Organic Rocks
Biochemical Rocks:
The biochemical sediments are produced when plants and animals living
under water, extract from it dissolved mineral matter usually calcite to
form Shell or other hard parts. Example – Limestone
Shale with Plant fossil
14. Most organisms are
uniquely adapted to
their habitat, and the
structure of fossil
organisms and
comparison to any
living relatives is useful
in determining ancient
depositional
environments
Fossils-Remains and
Traces of Ancient Life
16. Organically formed Rocks
Organic Rocks: Containing organic matter belongs this group. Example Coal
these are called carbonaceous rocks.
Formation of Coal
Coal
17. TEXTURES OF SEDIMENTARY ROCKS
• Origin of Grains
• Size of Grains
• Shape of Grains
• Packing of Grains
• Fabric of Grains
1) Origin of Grains:
Either Clastic or Non Clastic
2) Size of Grains:
• Coarse grain greater than 5 mm
• Medium grain in size 1 – 5 mm
• Fine grain less than 1 mm
18. TEXTURES OF SEDIMENTARY ROCKS
3) Shape of Grains
Angular, Sub Angular, Rounded, Sub Rounded.
• Sphericity and roundness of sediments / grains indicated
varying degree of abrasion and transport
Eg. Breccias : Angular and rough,
Conglomerates: Rounded Gravels
Angular in Shape - short distance transport from the source
Rounded in Shape - long distance transport
19. 4) PACKING OF SEDIMENTS / GRAINS:
Opened packed / densely packed.
Related to litho stratigraphic pressure.
5) FABRIC OF GRAINS:
Sedimentary rocks containing elongated particles and
their orientation demarks the flows of sediments.
• Example. Rhyolites: High degree of crystallization / parallel
axis of grains.
20. STRUCTURES OF SEDIMENTARY ROCKS
► Stratification
► Lamination
► Cross bedding or current bedding
► Graded bedding
► Ripple marks
► Concretionary Structure
► Minor Structure
21. STRUCTURES OF SEDIMENTARY ROCKS
1) Stratification:
The deposition of the sediments in to layer or beds are
called Stratification. The plane dividing different beds
are called bedding planes.
Bedding is most imp. Feature of a
sed.
Rock Beds are usually > 1 cm
Laminae < 1 cm
Orientation of bedding helps in
knowing the paleo-current
direction of the old rivers
22. STRUCTURES OF SEDIMENTARY ROCKS
2) LAMINATION:
The thin bedding less than 1 cm in thickness are
called Lamination. Lamination is found in very fine
grained rocks.
23. STRUCTURES OF SEDIMENTARY ROCKS
3) Cross bedding or current bedding
In this structure minor beds or laminations lie at an
angle to the planes of the general stratification.
Current bedding is commonly found in shallow water
and wind formed deposits. This structure shows
rapid change in the velocity and direction of flow of
streams or wind carrying sediments
Cross-stratified sst. Paleo-flow
from right to left
24. STRUCTURES OF SEDIMENTARY ROCKS
4) Graded bedding
In Graded bedding each bed shows a gradation in grain size
from coarse below to fine above. This results by rapid
sedimentation in water.
Grains at bottom coarse, at top fine
Graded bedding Structure
25. STRUCTURES OF SEDIMENTARY ROCKS
5) Ripple Marks:
The surface of some sedimentary deposits shows undulation or
ripple marks. These are produced by the action of waves and
current in shallow water, as well as on the surface due to wind
action
26. STRUCTURES OF SEDIMENTARY ROCKS
5) Minor Structures
Some bedding planes shows minor structures such as mud
crack, rain prints etc. these are found in fine grained
sedimentary rocks.
Mud cracks
Mud cracks
Foot Print Snake Print Rain Print
