Petrographic Education:
Tools, approaches, resources
Kitty Milliken
Department of Geological Sciences
Jackson School of Geosciences
University of Texas at Austin
Success of the Earth Sciences and the
Curriculum “Squeeze”
• “Traditional” geology curriculum
+
• Geophysics
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• Hydrogeology/Environmental geology
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• Additional math and supporting science
=
• Less time for petrography courses
Teaching Petrography
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Hands-on activity
Samples + microscopy equipment
Expert instructor
Repeated exposure to examples
Labor-intensive
The nature of petrographic instruction makes it
“expensive” in every sense of the word.
"...detailed petrographic work, sample
and core examination, outcrop work, and
even surface mapping are still an
important part of the solving the
exploration puzzle."
Thomasson, 2000, AAPG Explorer, p. 13.
Digital Sandstone Tutorial
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Non-intrusive interface
High-quality images
Interactive: rewards active inquiry
In-depth content
Abundant content
Supports varied patterns of use
Conveys sense of exploration
Version 1.0
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Focus on basics, for undergraduates
Around 300 images
Based on Folk Sandstone Class: Q, F, L, others
Architecture, compaction, texture
Exclusively light microscopy
Glossary for sedimentary petrology
Funded by NSF and the UT College of Natural
Sciences
Using the Tutorial
• Windows and Mac platforms
• Intel Pentium 120 Mhz processor
equivalent or faster
• 64 MB RAM
• 1024x768 pixel display
Building the Tutorial: the Team
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2 sandstone petrographers
1 carbonate petrographer/programmer
2 undergraduate geology majors
3 petrography instructors
5 petrography students
Building the Tutorial: the Tools
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Macromedia Authorware  6.0
Adobe Illustrator  8.0
Adobe Photoshop  5.5
.tif image formats converted to .jpeg,
800x600 pixels
Building the Tutorial:
the Process
• Scanned 35 mm slides
• Additional images by digital microscope
camera
• Mapped regions and text added to image
hard copies
• Digital image mapping
• Images placed into programmed
framework
Edit sheets for single
grains are very simple.
Image mappers knew enough
petrography to choose the
boundaries within some images
with very little input from the
petrographers.
Descriptions of more
complex images are
written on the computer,
printed, and attached to
the photomicrograph.
Diagenetic features can
present complex challenges
for image mapping.
C. Scripting algorithm
for each polygon
B. Transparent polygon
overlays
A. Digital photomicrograph
Sandstone
Clans
Quartzarenite
Arkose
Litharenite
Goals
Provenance
Diagenesis
Tutorial
Browse
Quiz
Other
sandstones
Mudrocks
An effective development strategy for digital teaching materials.
Testing the Tutorial
• GEO 416M: Sedimentary Rocks
• 65 students fall 2001, 80 students spring
2002
• Geology majors/petroleum engineers
• Laboratory grades: 3 sandstone exercises;
1 laboratory test
• Interviews by assessment specialist
• Evaluation form
Tutorial Effectiveness
Questions
respondants
Functions self-evident
53
Ease of navigation
53
Image quality
53
Artistic appearance
53
Entertaining
50
Level of use
52
Comparison to
hardcopy atlases
17
positive
92
91
64
47
42
65
negative
8
9
9
21
36
35
88
6
Individual grades
Tutorial Effectiveness
100
90
80
70
60
50
40
30
20
10
0
2001
2002
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10
20
30
40
50 60
70
Cumulative %
80
90 100
point gain
Tutorial Effectiveness
16
14
12
10
8
6
4
2
0
one std dev
<10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 >90
percentile group
Future Version 2.0
• Added graduate-level content
• Around 650 images: additional focus on
actual reservoir sandstones
• Added graphical content
• Other imaging methods: SEM, BSE, CL,
X-ray maps
• Expanded glossary
• Point-counting
Virtual Thin Sections
Main Content Pages
Virtual Thin Section Collections
• High-resolution preserves information
across a range of scale
• Links factual and interpretive information
to precise regions of the specimen
• Can be multi-author
• Can be authored repeatedly
• Are easy to duplicate and disseminate
(i.e., are secure for the long term)
Future of Petrography
• Fundamental to understanding low-temperature, nonequilibrium systems (including hydrologic systems).
• Integral to application of spatially-resolved chemical
analysis (microprobe, LA-ICP-MS, micro-drilling for
IRMS)
• Essential for understanding endolithic microbial
habitats
• A basic skill needed in the petroleum industry,
especially for deep drilling and non-conventional
reservoirs.
• Digital methods well-adapted for teaching highly
visual information.
• Geology majors adapt well to digital methods of
instruction
A Partial List of Petrographic Methods
• Hand lens
• Low-power stereo
microscopy
• High-resolution
transmitted light scanning
• Transmitted polarized
light microscopy
• Real-time high-resolution
3D light microscopy
• Confocal microscopy
• Polarized reflecting
microscopy
• UV-fluorescence
microscopy
• Cathodoluminescence
– Cold-cathode
– Scanned (Hot
cathode)
• Secondary electron
imaging
• Back-scattered electron
imaging
• Electron back-scattered
diffraction (orientation
contrast) imaging
• Charge-contrast imaging
• X-ray mapping (WDS,
EDS)