Transcript Correlation

Correlation
The dark layers of strata had been separated due to
erosion over many years.
Correlation is
the process
of showing
that rocks or
geologic
events from
different
places are of
the
same/similar
age.
The dark layers of
rock near the top of
the butte are of the
same age as the the
dark layers of rock
seen near the top of
the plateau in the
distance.
Correlation by Exposed
Bedrock
The Colorado River has
“cut” through layers of
sedimentary rock over
time.
One specific layer of rock
on one side of the river
can be “correlated” with
the same layer on the
other side of the river.
Both rock layers would
be of the same age.
Correlation by Similarities in
Rock
The claystone that
makes up the White
River Formation is
white-pink in color
and has a “chalky”
texture to it.
The claystone
found in Douglas,
WY is the….
The claystone
found in both
cities is of the
same age.
… same claystone
found in Ogallala,
NE some 250 miles
away!!
Fossils
A fossil is any
evidence of past
life.
Fossils can take
many forms.
Bone, teeth,
shells,
impressions/mold
of shells, skin
impressions,
footprints,
permineralized
bone and plant
material are all
examples of
fossils.
Correlation by Index
Fossils
Mucrospirifer is an example of an index fossil.
An index fossil is
evidence of past
life that …
LIVED FOR A
SHORT PERIOD
OF TIME
Mucrospirifer only lived during a period of geologic
time known as the Middle Devonian (398-385 mya).
SHORT PERIOD OF TIME
Rocks of Middle Devonian age can be found in areas of
western New York to areas as far west as Iowa.
WIDE GEOGRAPHIC AREA
and
CAN BE FOUND
OVER A LARGE
GEOGRAPHIC
AREA
Index fossils can
be useful tools in
correlation.
Mucrospirifer
Correlation by Index
Fossils
Location #1
Location #2
FOSSILS
A
B
Location #3
Location #4
Exposed strata is seen at four separate locations. Each
location is separated by 50 miles. Each layer within the
exposed strata is represented by a color. Each colored
layer represents a specific age of geologic time.
“Which fossil can be considered an index fossil?”
C
D
Correlation by Volcanic Ash/Meteor
Impact
A volcanic eruption
may discharge a
large amount of gas
and ash into the
atmosphere.
A meteoric impact
can discharge high
levels of iridium and
other rare elements
into the atmosphere.
Volcanic ash and
meteor impact
debris can be
deposited rather
quickly over a large
geographic area.
Like an index fossil,
a layer of volcanic
ash/meteoric debris
within rock strata
can be used as tool
for correlation.
The K/T Boundary is a thin layer of
sedimentary rock that is rich in iridium – an
element commonly found in celestial objects
(ie: asteroids) but rarely found on Earth.
The K/T Boundary represents a period of
geologic time (~ 300,000 yrs.) between the
Mesozoic and Cenozoic Eras.
The K/T Boundary can be found over a wide
geographic area.
K/T Boundary
The K/T Boundary represents the point of
dinosaur extinction.