Transcript Sedimentary Rocks - Red Hook Central School District

sedimentary
rocks
A. Formation:
1. Sedimentary rocks form
from the COMPACTION &
CEMENTATION of rock
fragments/sediments
2. Lithification: the changing
of sediments into
sedimentary rock
3. Sedimentary rocks are
similar to the sediments
from which they form (ie.
Sandstone is made up of
sand)
B. CLASTIC
1. Form when rock
fragments &
sediment are
carried & deposited
by GRAVITY,
WIND, GLACIERS,
& RUNNING
WATER
Clastic Rock Formation
Most sediment is carried by
Running Water
2. The further water
carries sediment, the
ROUNDER & SMOOTHER
the sediment becomes
3. When a stream slows
down, it drops the LARGEST
particles first, & the
SMALLEST last
(HORIZONTAL SORTING)
Observe how sediments are
deposited
So….
• If you are far out from shore, would
you expect the grain size of the
rocks to be large or small?
• What about if you are close to the
shore?
That means….
4. Rocks formed closer to
shore will be made up of
bigger fragments than
rocks formed farther
away from the shore
Conglomerate –
large sediments
that are rounded
(have been
transported by a
stream!)
Breccia – very large sediments
that are angular, most likely
deposited by gravity
C. CRYSTALLINE
1. Formed when dissolved minerals in
seawater are deposited (seawater
evaporates, leaving the minerals
behind to crystalize)
2. Also known as CHEMICAL
Salt “Mines” - Rock Salt is being formed
as the salt water evaporates from the sea.
“Devil’s Golf
Course” –
millions of
years ago this
was a sea of
salt water. It
has been
evaporating
over time…
…and has formed
“pockets” of
chemical
limestone, rock
salt, and rock
gypsum!
D. BIOCLASTIC
1. Formed from the remains of plants
& animals that are compacted
– Fossil Limestone – formed when
shell remains of marine organisms
are cemented in fragments
• Shells are made of CALCITE
which reacts with acid
2. Coal Formation
a. Long ago, huge trees grew
in the warm, humid swamps.
b. Trees died and
decomposed into what is
called PEAT
c. Peat was buried under
layers of mud.
d. Pressure increased, slowly
changing the plant remains
into coal.
Coal –
note
distinct
layering
of peat
ESRT page 7
STRATIFICATION
1. STRATIFICATION
(layering): Layers of
sediments that have
SIMILARLY colored
minerals and are typically
sandstones or siltstones
2. Fossils – actual remains, imprints
from plants or animals, or preserved
traces from living things
bells & whistles for sedimentary
rock identification!
• Stratification
• Fossils
• Fragments of materials
cemented together
• Ripple marks
• Mud cracks
Angel’s Landing, Zion Nat’l
Park, Utah – note rock layers
Red Sandstone, Utah – note distinct LAYERING of sediments (sand)
Horseshoe Bend, Utah
Grand Canyon Nat’l Park, Arizona – sedimentary rock
formation at its best! The canyons were formed by the
Colorado River cutting into the rock layers over time!
Fossils
• The remains, impression
or any other evidence of
a plant or animal
preserved in rock.
• Fossilization
Brachiopod fossils in limestone
Trilobite fossils – over 250 MILLION years old!!!
Imprint
of a leaf
Mud Cracks and Ripples
• Ripple Marks: A sand pattern formed
by the action of winds, streams,
waves or currents; preserved when
sand becomes sandstone
• Mud Cracks: Develop when deposits
of wet clay dry and contract. The
cracks are filled with sediments and
fossilize when the clay becomes
shale
Ripple Marks
in the Shale
from running
water as the
rock was
forming