Download Sedimentary Rock

Sedimentary Rocks are the product of
sediment deposition, diagenesis,
and lithification
Sedimentary Rock
http://soest.hawaii.edu/coasts/cgg_main.html
Oceans rise and fall, lakes come and go, streams run and disappear, deserts
become forests and forest become swamps…all these changes will be recorded
in sedimentary rocks
Sedimentary rock contains sediment grains, cement holding them together,
and empty space called “pores”
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To understand Earth history, a geologist seeks to interpret the
“Environment of Deposition” of a sedimentary rock…this reveals
something about changes occurring on Earth’s surface
Glacial Environment – grains very coarse
with no sorting, but
usually rounded
Eolian Environment – grains of uniform size “well sorted”
Landslide Environment – grains very coarse
with no sorting, with no
rounding
Coastal Environment – grains coarser and of mixed size
Marsh/Mudflat Environment – grains very fine
Stream Environment – grains much coarser and “poorly sorted”
Sedimentary Structures….
Evaporite environment – chemical sediments
Cross-beds – former dunes
Reef environment – biological sediments
Sedimentary rocks tend to form
layers or strata…each layer records
a depositional event
Deep sea environment?? – Plankton sediment and
clays from land
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Sediment becomes sedimentary rock…the texture and composition
of the sediment determine the type of sedimentary rock
Ripple
marks
modern
Mud
cracks
ancient
Two types of sedimentary rock –
Clastic Sedimentary Rock –
made of pieces of broken crust
Biochemical Sedimentary Rock –
made of precipitated minerals
Clastic Sedimentary Rock
Biochemical Sedimentary Rock
Conglomerate/Breccia –
gravel texture
Limestone –
CaCO3 composition
Sandstone –
sand texture
Conglomerate
Rock Salt
Chert –
SiO2 composition
Shale –
silt/clay texture
Coal –
Carbon composition
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How
does
coal
form?
Coal strip mine…
Pressure forms coal
Environments of deposition
Sedimentary texture
Sediment composition
Global Climate history
Clastic – Biochemical sedimentary rox
Breccia/Conglomerate
Sandstone
Shale
Limestone
Chert
Coal
How does coal form?
Sedimentary structures
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But why was there an ice age?
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Ice stores O16 so that oceans are O16
depleted in an ice age
+ O18/O16 -
Periodicity
y of 100,000
,
yrs
y
CaCO3
41 kyrs
21 kyrs
Layer by layer
sampling of plankton
reveals oxygen
isotope record
100 kyrs
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These were made
during an ice age!
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