This document provides information about a petrology course for the 2008-2009 semester. The course includes 2 credits of theory and 1 credit of practical work. It is taught by Hill Gendoet Hartono on Mondays from 9:50-10:40 and 10:45-11:35. The document then provides detailed information about sedimentary rocks, including descriptions of different types of clastic rocks like breccias, conglomerates, sandstones and shales. It also discusses carbonate sedimentary rocks, chemical sedimentary rocks, and the environments and processes involved in forming different sedimentary rocks.

1. Semester 2, 2008-2009
petrologi
2 SKS teori
1 SKS praktikum
by:
hill. gendoet hartono
Senin, jam 09.50 – 10.40
jam 10.45 – 11.35

3. Clastic Rocks - Hand Specimens
 Breccias: angular particles
 Conglomerates: rounded particles
 Sandstones
 Quartz sandstone: dominated by quartz
grains
 Arkose sandstone: composed of qtz & fsp
grains
 Graywacke: dominated by lithic (rock)
fragments
 Shales: mud and silt particles

4. Sedimentary Rocks
 Detrital/Siliciclastic Sedimentary Rocks



conglomerates & breccias
sandstones
mudstones
 Carbonate Sedimentary Rocks
 limestones
 dolostones
 Other Sedimentary Rocks





evaporites
phosphates
organic-rich sedimentary rocks
cherts
volcaniclastic rocks

5. Detrital Sediments & Sedimentary
Rocks
gravel
&
conglomerate
sand
&
sandstone
clay, silt
&
mudstone

8. Types of sedimentary rocks
Chemical rocks – sediment
from ions that were once in
solution
Detrital rocks –sediment
transported as solid particles

9. Detrital sedimentary rocks
 Constituents of detrital rocks can
include
Clay minerals
Quartz
Feldspars
Micas
 Particle size is used to distinguish
among the various types of detrital
rocks

10. Detrital sedimentary rocks
Mudrocks: grains less than .06 mm
 1. Mud: small particles easily kept in
suspension
 Settles only in quiet water
 Rock types include Shale: mud-sized particles
<.004 mm deposited in thin bedding layers
called laminae
The most common sedimentary rock
2. Larger mudrock grains called silts
silt-sized particles .004-.06 mm
Gritty grains can be felt

11. Mudrock (Shale) containing plant fossils
lamellae
Fossil Leaves Wilkes Barre, PA

12. Detrital sedimentary rocks
Sandstones
 Made of sand-sized particles .064 – 2
mm … Sand is a size!
 Forms in a variety of environments
 Sorting, angularity and composition
of grains can be used to interpret the
rock’s history
 Quartz is the predominant mineral
(due to its durable nature)

13. Sandstone (note large number of quartz grains)

14. Classifying Sandstones
Photomicrograph of quartz rich sandstone (Arenite)
Grains subangular to subrounded, sandstone is poorly sorted
Plagioclase grain
Making thin sections

15. Types of Sandstone
 Quartz Arenite >90% quartz grains
 Beach and dune deposits
 Arkoses >25% feldspar, angular, poor
sort.
 Transform boundaries; exposed granites
 Any felsic rock eroded, not transported far
 Graywackes Quartz, feldspar, volcanics



Port sorted, angular
Erosion of Island Arcs
Rift Valley Sediments

16. Detrital sedimentary rocks
Conglomerate and breccia
 Both composed of particles > 2mm in
diameter
 Conglomerate consists largely of
rounded clasts
 Breccia is composed of large angular
particles

17. Conglomerate

18. Breccia (shattered rock accumulates at the base of a cliff)
Note sharp angular clasts

19. Energy
 Coarse sediments are deposited in high
energy (fast water) environments such as
under breaking waves at the beach, or in
the beds of fast streams.
 Fine sediments are deposited in low
energy environments, e.g. the slow water
of deep lagoons, the abyssal plain, etc.

20. Outcrop of conglomerate
with cobble-sized clasts
interbedded with sandstone
Conglomerates are fastwater sediments
“High Energy”
K.E. = 1/2mv2
In fast water, smaller sizes
swept away

21. Chemical sedimentary rocks
 Precipitated material once in solution
 Precipitation of material occurs two
ways:
Inorganic processes: the minerals
precipitate out of water
Organic processes: animals and plants
precipitate the minerals to use as shells
or skeletons
A foraminiferan,
a type of microfossil
http://www.ucmp.berkeley.edu/collections/micro.html

22.  Common chemical sedimentary rocks
Limestone
 Most abundant chemical rock
 Made of the mineral calcite CaCO3
 Marine biochemical limestones form
as coral reefs, coquina (broken
shells), and chalk (microscopic
organisms)
 Inorganic limestones include
travertine (caves) and oolitic
limestone (Bahamas)

23. Coquina

24. Fossiliferous limestone
Note shells and lime matrix

25. Chalk Outcrops in SE USA
Chalk
Hand Specimen

26. Inorganic Chemical Sediments
Ooids under microscope
Oolitic Limestone - Bahama Shoals
Oolitic Limestone - Hand Specimen

27.  Other chemical sedimentary rocks
 Chert
 Made of microcrystalline quartz
 Usually deposited as siliceous ooze in deep
oceans (can be diatomaceous)
chert
Diatomaceous chert

28.  Other chemical sedimentary rocks
 Dolostone (made of mineral Dolomite)
 Like Calcite, but some Ca is replaced by Mg
The Dolomites, sediments thrust up when the Alps formed

29. Evaporation
How to make Dolomite
6_19
Limestone
Seawater enriched
in Mg2+
Mg2+ -rich seawater circulates
Dolostone
through porous limestone
Mg2+ replaces some of the
Ca2+ in limestone

30. http://www.ndsu.nodak.edu/instruct/ashworth/coursework/g410/evaporites/saltbeds.jpg
 Common chemical sedimentary
rocks
Evaporites
Evaporation triggers
deposition of chemical
precipitates
Examples include rock salt
and gypsum

31. Chemical sedimentary rocks
 Common chemical sedimentary rocks
 Coal
 Different from other rocks because
it is composed of organic material
 Stages in coal formation (in order)
1. Plant material
2. Peat
3. Lignite
4. Bituminous

32. Stages in coal formation

33. Sedimentary Environment
 Is the geographic setting where
sediment accumulates
 Determines nature of sediment that
accumulates (grain size, shape, etc.)

34. Character of detrital sediments depends on time, distance,
and energy. For 6_5
example, in streams:
Particles are large and
irregular, and consist of
a variety of lithologies,
including the least
resistant.
Particles are mid-sized
and of intermediate
sphericity, and include
resistant and nonresistant
lithologies.
HIGHLANDS
LOWLANDS
Particles are small and
nearly spherical, and
consist mainly of the
most resistant lithologies,
such as quartz.
NEAR-COASTAL

35. Clastic wedges

36. Sediment Maturity
Sediment Maturity is
indicated by decreasing
clay content, increasing
degree of size sorting,
and increasing rounding
of grains within the
deposit
Poorly sorted
Well sorted
Sorting refers to the range
of particle sizes in the
sediment
Well-sorted - uniform grain
size
Poorly-sorted - mixture of
grain sizes
immature
OCNG 251
mature
Texas A&M University
Oceanography

37. We can recognize past floods
Floods change the local
conditions
6_6
Fine-grained sediment
on floodplain
Older sediment
1
Pre-flood
Bounders on
bottom, sands
and muds
suspended
Flood water
Erosion of uppermost
fine-grained sediment
2 Flood stage
Flood: One source of
Graded Bedding
3
Post-flood
Fining-upward
flood deposit
Bedding plane is an
erosional surface

38.  Types of sedimentary environments
 Continental
 Streams
 cross beds from ripples, fine mud w/ cracks
on floodplain
 Lakes – Fine parallel lamellae - Varves
 Wind (dunes) well sorted, frosted grains
 Glacial Ice: Poorly sorted, unstratified
 Marine
 Shallow (< 200 meters deep) carbonate-rich
sands, muds
 Deep (seaward of continental shelves)
microfossils, volcanic ash, turbidites

39.  Types of sedimentary environments
Transitional (shoreline)
 Tidal flat Sands w/ symmetrical ripples
Lenses of tidal creek muds
 Lagoons – including Bays behind Barrier
Islands.
Organic rich black muds and sands
 Deltas
Complex, e.g. Sandstones w/ large
foresets at seaward face

40. A picture glossary of sedimentary
Turbidite: underwater landslide
= graded bedding
environments

41.  Sedimentary Facies
Different sediments accumulate
next to each other at same time
Each unit (called a facies) possesses
a distinctive characteristics
reflecting the conditions in a
particular environment
The merging of adjacent facies
tends to be a gradual transition

42. Some facies in an oversimplified drawing
Abyssal Ooze
Stillwater muds
Nearshore sands

43. Sedimentary structures
 Tell us something about past
environments
 Types of sedimentary structures
Strata, or beds (most
characteristic of sedimentary
rocks)
-bedding planes that separate
strata caused by variation in
deposition

44. Strata- Bedding Planes

45. Fine Scale Bedding- Lamellae

46. Recognizable Sedimentary Structures
 Types of sedimentary structures 1
Graded beds: waning flow (flood, turbidite)
 Sediments become coarser upward
Determines “Right side up”

47. Graded Beds – grains fine upward
Note: Beds were tilted from horizontal after deposition

48. Recognizable Sedimentary Structures
 Ripples
Irregularities in bottom sediment lead to
ripples
Asymmetric types indicate flow
direction.
Symmetric types formed in tidal areas

49. Cross Beds – ripples in cross section
 In cross section these look like lines
at an angle to the horizontal – “cross
beds”
 Form determined by velocity and size
of particles.

50. Slabs of eroding sandstone with ripple marks

51. Cross bedding in Sand Dune deposits
Navaho Sandstone
Sand Dune? Look for Frosted Grains
Shoreline of
an interior
seaway
Sandstone deposited
in ancient sand dunes
Frosted Grains

52. Recognizable Sedimentary Structures
 Types of sedimentary structures 3
 Non-marine
Mud Cracks – floodplains, playas
Also good for right side up

53. Mud Cracks: clay layer shrinks during drying, curls
upward; cracks fill next flood

54. Mudcracks indicate drying events.
Geologists can determine if rocks overturned.

55. Sedimentary Environments
 Sediments are formed in many different
environments
 Each have characteristic appearance
today, features that allow them to be
recognized in the geologic record

56. Fresh Water Facies
Streams (includes big Rivers), with
floodplains and levees, called fluviatile. The
Point Bar Sequence is typical for meandering
streams. Cutoffs generate Oxbow deposits.
•
High gradient streams with high sediment
load are Braided.
• Lake deposits called lacustrine, generally
still waters, often varved deposits if winters cold
http://hays.outcrop.org/gallery/rivers/arid_meander?full=1

57. Point-bar Sequence:
Deposits Associated with
Meandering Streams
Meandering
Stream
OxBow
Floodplain
http://hays.outcrop.org/gallery/rivers/arid_meander?full=1

58. Point Bar Sequence
Fines of Floodplain
Crossbeds of Bar
Gravel of bed
Erosion

59. Terms for Marine (i.e. Ocean) Environments
6_27
and some characteristic sediment facies
Continental
shelf
Shallo
w
marin
e
Continental
slope
Abyssal
Plain
Dee
p ma
rine
Submarine
volcanoes

60. Facies changes due to rising sea level - water getting deeper everywhere
River
6_29
Direction
of migration
of shoreline, and landward
shift of sedimentary facies
Time B
Shoreline at
time B
Time A
Shoreline at
time A
Shallow
marine
Beach
River
Sea level
rising
Deep
marine
Shallow
marine
Beach
Comparison of sediments deposited
Deep
marine
Shallow
marine
Deposited
at time A
Deposited
at time B
REMEMBER: the facies
follow the shoreline

61. Fossils: Evidence of past life
 By definition, fossils are the traces or
remains of prehistoric life now preserved in
rock
 Fossils are generally found in sediment or
sedimentary rock (very rarely in
metamorphic or igneous rocks)

62. Fossils: Evidence of past life
 Geologically fossils are important for
several reasons
 Aid in interpretation of the geologic past
 Serve as important time and environment
indicators
 Allow for correlation of rocks from different
places

63. 3 Billion Year Old Algal Mounds (Stromatolites) Australia
CO2 in
O2 out

64. Natural casts of
shelled invertebrates in limestone

65. Dinosaur footprint in mudstone
Dilophosaurus Jurassic Park Dennis Neary and Peter Dodson