Stratigraphy

1
Stratigraphy

• Stratigraphy is the branch of geology that deals
  with the arrangement of rocks in layers.

2
http//guest.portaportal.com/ckaznosky Google
images
3
(No Transcript)
4
Relative Dating

• The procedure by which scientists determine the
  geologic events which formed these rocks and the
  order in which these events occurred.

5
Law of Uniformitarianism

• The geologic processes which shape the earth
  today are the same as they were in the past.
• The present is the key to the past

6
(No Transcript)
7
(No Transcript)
8
Law of Superposition

• In an undisturbed sequence, each rock later is
  older than the layers above it.
• Oldest on the bottom, youngest on the top.

9
(No Transcript)
10
Law of Original Horizontality

• Sediments are always deposited in horizontal
  layers. If sedimentary rock layers are not
  horizontal, then an event like folding,
  faulting,intrusions, etc. took place to change
  the layers after they were deposited.

11
(No Transcript)
12
Law of Cross-Cut Relationships

• If a fault or an igneous intrusion cuts across
  or through rock layers, then the fault or
  intrusion is younger than the rock layers.

13
(No Transcript)
14
(No Transcript)
15
the Law of Crosscutting Relationships stated that
if a fault or other body of rock cuts through
another body of rock then it must be younger in
age than the rock through which it cuts and
displaces.
16
(No Transcript)
17
Principle of Unconformity

• Often the deposition of rock layers is stopped
  for one reason or another and the layers undergo
  erosion. This causes a break in the geologic
  record. This break or missing time sequence is
  called an unconformity. There are 3 types of
  unconformities.

18
A. Disconformity

• The sedimentary rock area is eroded, then
  undergoes deposition without any change in the
  angle of the rock layers. The old erosional
  surface is parallel to the beds above and below
  it.

19
DISCONFORMITIES Disconformities are
characterized by an irregular erosional surface
which truncates flat-lying sedimentary rocks. The
layers of sedimentary rocks above and below the
unconformity are parallel with one another.
20
(No Transcript)
21
(No Transcript)
22
B. Angular Unconformity

• When sedimentary rock layers are tilted,
  exposed to the new surface and then eroded, and
  covered by new deposits, an angular unconformity
  results. The new layers ARE NOT parallel to the
  older layers.

23

24
ANGULAR UNCONFORMITIES Angular unconformities are
characterized by an erosional surface which
truncates folded or dipping (tilted) strata.
Overlying strata are deposited basically parallel
with the erosion surface. The rocks above and
below the unconformity are at an angle to one
another.
25
(No Transcript)
26
C. Nonconformity

• This occurs when igneous or metamorphic rocks
  are eroded and younger sedimentary rocks are
  deposited on the erosional surface.

27
NONCONFORMITIES Nonconformities are
characterized by an erosional surface which
truncates igneous or metamorphic rocks. At a
nonconformity, sedimentary rocks unconformably
overlie igneous or metamorphic rocks.
28

Angular Unconformity
Disconformity
Nonconformity
29
Cambro-Ordovician sea floor life.
30
Relative time scale
Faunal succession. Selected members of the
long-extinct group, trilobites, indicate changing
styles with time
31
Evolution of life Correlating rocks, etc.
Correlation by fossils. Certain index fossils are
keys to matching sedimentary strata in widely
separated outcrops
32
Fly reserved in amber for over 3 million years.
33
Carbonization conversion to coal carbon film
impressions
34
PRACTICE
35

• Shale
• Sandstone
• Shale
• Conglomerate
• Shale
• Limestone
• Tilting
• Angular unconformity
• Igneous (granite)
• Shale
• Sandstone

36
(No Transcript)
37

• B
• G
• C
• D
• E
• H
• A
• F

38
(No Transcript)
39

• A
• C
• E
• D
• B
• F

40
(No Transcript)
41

• B
• D
• C
• A
• E
• F

42
(No Transcript)
43

• E
• G
• L
• C
• H
• M
• D

• J
• A
• N
• K
• B
• F