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Lecture 7
Sediments and Sedimentary Rocks
Physical Geology
Lecture Outline
I
A)
B)
Definitions
Sediment
Transportation
i.
ii.
iii.
Fluid Dynamics
Modes of Transport
Transport-Related Properties
C)
D)
Deposition
Lithification
A)
Clastic Rocks
II
Sedimentary Rocks
i.
ii.
iii.
Breccia and Conglomerate
Sandstone
Fine-Grained Clastic Rocks
i.
ii.
Carbonates
Evaporites
B)
Chemical Sedimentary Rocks
C)
Organic Sedimentary Rocks
A)
B)
C)
Source Area
Depositional Environment
Plate Tectonics and Sedimentary Rocks
III
IV
Sedimentary Structures
Interpretation of Sedimentary Rocks
Physical Geology
Definitions
sediment - solid fragmental material transported and deposited by wind, water, or
ice, chemically precipitated from solution, or secreted by organisms, that forms
in layers in loose, unconsolidated form.
unconsolidated material - A sediment that is loosely arranged or unstratified, or
whose particles are not cemented together, occurring either at the surface or at
depth.
sedimentary rock - A layered rock resulting from the consolidation of sediment.
Physical Geology
Grain Size
Udden-Wentworth Scale
Physical Geology
Sediment Transport
Water
Wind
Gravity
Ice
Physical Geology
Sediment Transport
Fluid Dynamics
Physical Geology
Sediment Transport
Modes of Transport
Dissolved Load
Suspended Load
Bed Load
•Saltation
•Rolling (Surface Creep)
Physical Geology
Sediment Transport
Transport-Related Properties
Physical Geology
Deposition of Sediment
deposition - the laying-down of rock-forming material by any natural agent
deposit - Earth material of any type that has accumulated through the activities
of water, wind, ice, or other agents, such as precipitation.
depositional environment - the location in which deposition occurs
Physical Geology
Deposition of Sediment
Progressive Sorting
Physical Geology
Lithification of Sediment
lithification - the conversion of newly deposited sediment into a solid rock. It may
be concurrent with, soon after, or long after deposition.
Cementation
Compaction
Crystallization
Physical Geology
Lithification of Sediment
Compaction
compaction - reduction in bulk volume or thickness of
fine-grained sediments, owing to increasing weight
of overlying material that is continuously being
deposited, or to pressures resulting from earth
movements. Tighter packing of sedimentary
particles results in a decrease in porosity.
Physical Geology
Lithification of Sediment
Cementation
cementation - the process by which clastic sediments
are converted into rock by precipitation of a mineral
cement among the grains of the sediment.
cement - chemically precipitated mineral material that
occurs in the spaces among the grains of a sedimentary
rock, thus binding the grains into a rigid mass.
The most common cements are silica, carbonates, and
iron oxides.
Physical Geology
Lithification of Sediment
Crystallization
crystallization - the development and growth of crystals by
precipitation from solution at or near the Earth's surface.
Physical Geology
Sedimentary Rocks
Clastic
Chemical
Organic
Physical Geology
Sedimentary Rocks
Clastic Rocks
Physical Geology
Sedimentary Rocks
Clastic Sedimentary Rocks - Examples
conglomerate
sandstone
siltstone
graywacke
shale
breccia
Physical Geology
Sedimentary Rocks
Chemical Sedimentary Rocks
Carbonates
Evaporites
Physical Geology
Sedimentary Rocks
Chemical Sedimentary Rocks - Carbonates
(Bioclastic Limestones)
coquina
chalk
coralline limestone
Physical Geology
Sedimentary Rocks
Chemical Sedimentary Rocks - Carbonates
(Inorganic Limestones)
travertine
oolitic
limestone
tufa
Physical Geology
Sedimentary Rocks
Chemical Sedimentary Rocks - Evaporites
rock salt
NaCl
anhydrite
CaSO4
rock gypsum
CaSO4. H2O
Physical Geology
Sedimentary Rocks
Organic Sedimentary Rocks
peat
lignite
coal
Physical Geology
Sedimentary Structures
Definitions
sedimentary structure - a feature in sedimentary rock, formed either
contemporaneously with deposition (primary structure) or by later
sedimentary processes (secondary structure)
bedding - the arrangement of sedimentary rock in layers
bedding plane - division plane that separates each successive sedimentary
layer or bed from the one above or below. It commonly marks a
visible change in lithology or color.
formation - a body of rock strata that consists dominantly of a certain lithologic
type or combinations of types. It is the fundamental lithostratigraphic
unit. Formations may be combined into groups and subdivided into
members.
Physical Geology
Sedimentary Structures
Stratification
Internal Structures
Bedding Plane Structures
Geopetal Structures
Physical Geology
Sedimentary Structures
Stratification
stratification - the arrangement
of sedimentary rocks in strata;
bedding. It may be indicated
by differences in texture,
cementation, color, or
composition.
Physical Geology
Sedimentary Structures
Stratification - Principle of Superposition
Physical Geology
Sedimentary Structures
Stratification - Principle of Original Horizontality
Physical Geology
Sedimentary Structures
Internal Structure
graded bedding
cross-stratification
Physical Geology
Sedimentary Structures
Cross-Bedding
Physical Geology
Sedimentary Structures
Graded Beds
Physical Geology
Sedimentary Structures
Bedding Plane Features
Mudcracks
Ripples
Fossils
Physical Geology
Bedding Plane Sedimentary Structures
Ripples
Lecture 7
III.F
Physical Geology
Bedding Plane Sedimentary Structures
Mudcracks
mudcrack - an irregular fracture in a crudely polygonal pattern, formed by the shrinkage of
clay, silt, or mud, generally in the course of drying under surface conditions.
Physical Geology
Bedding Plane Sedimentary Structures
Fossils
Physical Geology
Sedimentary Structures
Geopetal Structures
geopetal - pertaining to any rock feature that indicates the relation of top to bottom at the
time of formation of the rock
symmetric ripple marks
included fragments
cross-bedding
graded bedding
mud cracks
bed surface marks
scour marks
fossils
Physical Geology
Interpretation of Sedimentary Rocks
Grain Size
Lecture 7
IV
Physical Geology
Interpretation of Sedimentary Rocks
Color
Physical Geology
Depositional Environment
Continental
Transitional
Marine
Physical Geology
Plate Tectonics and Sedimentary Rocks
Passive Margin
Physical Geology
Plate Tectonics and Sedimentary Rocks
Volcanic Island Arcs
Physical Geology
Plate Tectonics and Sedimentary Rocks
Continental Collision