Download sedimentary rocks - MrDanielASBSukMSSci

Lithification
Sediments
Deposition
Transport
Erosion
Weathering
Sedimentary Rocks
From Sediment to Rock
• Most sedimentary rocks are formed through a series
of processes: erosion, deposition, compaction, and
cementation.
Weathering
The sediments that make up sedimentary rocks are produced by:
Mechanical & Chemical Weathering
Mechanical Weathering
Chemical Weathering
Mineral
Stability
Products of Weathering
• Lithic (Rock) Fragments
(granite, basalt, schist, etc.)
• Dissolved Ions
(Calcium, Potassium, Sodium, etc.)
• Rust Minerals (Hematite, Goertite, etc.)
• Clay Minerals
(Bentonite, Montmorillonite, etc.)
• Residual Minerals
(Quartz, Orthoclase, Muscovite, etc.)
Erosion & Transport
Water
Wind
Ice
Gravity
Deposition
Lithification
Sediment
Rock
Cementation
Typical Cement:
•Calcite
•Quartz
Sedimentary Rocks
Identification
Note: Use the same terms to describe
sediments & sedimentary rocks.
Only difference is lithification!
Rock Identification is based on:
• Composition
What minerals make
up the rock?
• Texture
What is the shape, size
and orientation of the
mineral grains that
make up the rock?
Major Difference:
Crystalline vs. Clastic
Types of Sedimentary Rocks
Detrital Rocks
Chemical Rocks
vs.
Difference: Texture
Detrital (Clastic Texture)
vs.
Chemical (Crystalline Texture)
Detrital Rock Composition
Detrital Rocks
• Lithic Fragments
• Quartz
• Clay Minerals
• Fossil Fragments
• Rust Minerals
• Orthoclase
• Muscovite / Biotite
Detrital Rock Texture
Clastic Texture
• Grain Size
• Grain Sorting
• Grain Rounding
• Sediment Maturity
Grain Size
•Gravel
2mm
•Sand
1/16 mm
•Mud - Silt
1/256 mm
•Mud - Clay
Detrital Rock Names
(Based Primarily on Grain Size)
Gravel Sized:
Conglomerate
Sand Sized: Sandstone
Mud Sized:
Mudstone
Siltstone
Shale
Sorting
Grain Roundness
Gravel Sized Detrital Rocks
(Subdivided Based on Grain Roundness)
Conglomerate
Breccia
Maturity
Mature
•Well Sorted
•Well Rounded
•All Quartz
Immature
•Poorly Sorted
•Angular grains
•Mixed Composition
including clay
Quartz Sandstone
Lithic Sandstone
Arkose (Sandstone)
Sandstones
(Subdivided based
on maturity)
Greywacke
Sandstones Under a Scope
Detrital Sedimentary Rock ID
Clastic (Detrital) Sedimentary Rocks
Grai n Size
Roundne ss
Sorting
Composi tion
Name
Rounded
Moderate to
poor
Fragme nts of any rock type
CONGLOMER ATE
Angular
Moderate to
poor
Fragme nts of any rock type
BRECCIA
Rounded
Well
All Quartz - usually white to tan
QUAR TZ
SANDSTO NE
Subrounded to
Angular
Moderate to
poor (few
grains
>2mm)
Feldspar (usually orthoclase), micas,
quartz, and other minerals
ARKO SE (Arkosic
Sandstone)
Subrounded
Moderate to
well
Quartz, lithic fragments, and other
mine rals
LITHI C
SANDSTO NE
Rounded to
angular
Moderate
Quartz and rock fragments mixed
with >15% clay; often gray colored
GRAYWA CK E
SANDSTO NE
(to small to
see)
Well
Clay and quartz (but usually too
small to see)
SILTSTONE
Clay (but usually too small to see);
Massive
MUDS TONE
Clay (but usually too small to see);
Breaks into semi-flat layers
SHALE
Gravel-sized
(> 2 mm)
Sand-sized
(visible grains
up to 2 mm)
Silt-sized
(feels gritty)
Clay-sized
(feels smooth)
(to small to
see)
Well
Chemical Rock Texture
Crystalline Texture
• Coarse
• Fine
Chemical Sedimentary Rocks
(Names based primarily on composition)
Composition
• Calcite
• Quartz (silica)
• Halite
• Gypsum
• “Carbon” / Plant
Remains
Basic Rock Name
• Limestone
• Chert
• Rock Salt
• Rock Gypsum
• Peat or Coal
Chemical Rocks
(Names based mainly on composition)
Limestones
Crystalline
Limestone
Fossiliferous Limestone
Chalk
Chemical Rocks (cont.)
Evaportites
Chert
Rock Salt
Rock
Gypsum
Coal
Chemical Sedimentary Rock ID
Chemical, Biochemical & Organic Sedimentary Rocks
Composi tion
Calcite (acid
reaction)
Dolomite
(acid reaction)
Texture
Name
Crystalline - medium to coarse (visible) grains
CRYST ALLINE
LIMESTONE
Crystalline - grains too small to see
MICR ITE
Abundant fossils in a fine- to coarse-grained crystalline matrix
FOSSILIFEROUS
LIMESTONE
Fine-grained powder, earthy smell (often black, gray, or white)
CHA LK
Crystalline - fin e to coarse grained
DOLOSTONE
Quartz
(scratches
glass)
Crystalline - grains too small to see; conchoidal fracture
CHE RT
Fine-grained powder, earthy smell (no acid reaction) (often white)
DIA TOMIT E
Gypsum
Crystalline - fin e to coarse grained
ROCK GYPS UM
Halite
(tastes salty)
Crystalline - fin e to coarse grained
ROCK S ALT
Fibrous, brownish plant material; soft
PEAT
Dense, black masses; depending on grade may be dull to vitreous;
lower gra des may contain minor fossils
COAL
Plant Remains
(Carbon)
Sedimentary Rocks on Earth