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uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
uAbstract
uFigure
captions
uIntroduction
uExisting
atlases
uTutorial
goals
uUsing
tutorial
uOngoing
activities
uAcknowledgements
uReferences
uTable:
Web Links
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Figure
Captions
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Figure 1. The main page provides links to all the major components of
the tutorial. The pull-down menu at the top left of the window (“Go”)
also allows the user to leap to any of the four second-level pages of
the tutorial or any of the major subject areas featured on the top-level
page. For example, click on “Arkose” to view the Arkose sub menu screen
(Figure 2).
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Figure 2. Arkose sub menu screen, obtained by clicking on the “Arkose”
link of the main page (Figure 1).
Each Provenance
and Diagenesis section is further subdivided into “Goals”, “Browse”, and
“Tutorial” sections. Click on the Diagenesis “Browse” link to view
thumbnails of photomicrographs (Figure 3).
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Figure 3.
Diagenesis thumbnails obtained by clicking on the Diagenesis
“Browse” link of the Figure 2 showing 16 thumbnails of photomicrographs.
Note that this particular section in the tutorial has two more pages of
thumbnails that can be accessed by clicking on the right arrow button.
Clicking on one of the “K-spar overgrowth” thumbnail brings the user
into main tutorial window (Figure 4).
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Figure 4. Image of K-spar overgrowth in main tutorial, where the “Info”
button has brought up general information on the sample.
(In tutorial,
clicking anywhere else in the screen will erase the information text
box.) Click on the center of the image to view a text box explaining the
secondary porosity (Figure 5).
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Figure 5. Same image of K-spar overgrowth as in Figure 5.
Clicking on
the center of the image has brought up a text box explaining that
secondary porosity was developed by the dissolution of detrital
plagioclase, which is stained pink. Notice that the term “secondary
porosity ” is colored and underlined, indicating the presence of a
hyperlink. (In the tutorial, clicking on “secondary porosity ” accesses
the glossary entry for secondary porosity ).
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Figure 6. Plane polarized light view of the Permian Lyons Sandstone from
Central Colorado, a classic quartzite. Click on the “PPL/XPL” button to
view cross-polarized light view (Figure 7).
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Figure 7. Cross-polarized light view of the same field as that in Figure
6. Clicking on the “PPL/XPL” button has brought up this cross-polarized
light view. Subsequent click on the same button brings back the plane
polarized light view (Figure 6).
Click on
“History” button to view ‘Previous Pages’ window ((Figure
8). Click on “Search” button to view ‘Search Sandstone Petrology’
window (Figure 9).
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Figure 8. Clicking on the “History” button has brought up ‘Previous
Pages’ window where the user can view again previously visited image by
double clicking on the image name from the list.
Here image of Qz
Sandstone #18a is viewed by this procedure. Click
on "Search" button to view 'Search Sandstone Petrology'
window (Figure 9).
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Figure 9.
Clicking on the “Search” button has opened ‘Search Sandstone Petrology’
window. The user can type in any combination of search criteria here;
search example using search criteria “primary porosity ” is shown here.
From the search result, double clicking on the image name (Qz Sandstone
#33a) has brought the user to that page.
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Return
to top.
Introduction
Petrography, description and
interpretation of rock properties at the microscopic scale remains,
fundamentally, a qualitative field of study highly dependent upon the
involvement of a trained observer. However, instruction in petrography
in the universities, where it is still practiced, remains largely
unchanged since the 19th century. A trend toward removing petrographic
experience from university curricula arises primarily because of
economic considerations relating to the labor-intensive character of
petrographic instruction, yet the practical value of such training
remains and is becoming a concern of industry professionals who seek to
hire students possessing basic skills in rock description (Thomasson,
2000). Preserving petrographic studies in the modern curriculum
requires that new, more cost efficient methods be devised for passing
skills from instructor to student. This project attempts partially to
mimic the highly visual and interactive character of traditional
petrographic instruction with the goal of training and motivating
students in the use of these methods. Preserving petrographic studies is
also important for the petroleum industry and service companies because
forward numerical models for risk analysis, porosity prediction, and
reservoir characterization derive petrographic data such as texture and
sandstone composition from point-count analysis of analog thin sections
(Lander
and Walderhaug, 1999;
Walderhaug, 2000). Thus, this type of digital petrographic tutorial
could potentially contribute to achieving standardized and high-quality
petrographic work.
Existing Petrographic Contents In
Multimedia Format
An online search of Science Citation
Index (http://wos.isiglobalnet.com/)
reveals that digital atlases and tutorials have been most extensively
applied in the area of medical education. This is perhaps not surprising
as many medical specialties, similar to petrography, require students to
assimilate vast amounts of visual information on form, distribution, and
morphological variation of natural structures. The potential advantages
of digital imaging methods for distribution of petrographic data have
been recognized (e.g.,
Carrozzi, 1996). Material currently available, either web-accessible
(Table
1) or published on publicly available CDs (e.g.,
Christiansen, 2001) is limited, however. In part, the limited
availability of these materials may reflect the labor-intensive nature
of content development as well as the shrinking pool of experts capable
of authoring petrographic tutorials. Web-accessible petrology materials
fall into two general categories: (1) image collections ranging from a
few to around 100 images, which tend to have little interpretive
material keyed to particular images and almost none keyed to particular
features within the images, and (2) tutorials based on existing lecture
series. The latter type of tutorial tends to be arranged somewhat like
conventional textbook, making little use of the interactive
cross-referencing capabilities of multimedia authoring.
Return
to top.
The
Goals Of Current Tutorial
1. Expose students to a large and diverse amount of visual material,
comparable to that formerly provided in petrographic laboratory
activities that have been largely displaced from the curriculum.
2. Allow students to attain a higher level of expertise in rock
description than current instructional practices allow by the use of
substantial interpretive material and an interactive structure that will
guide the student through a process that will itself promote absorption
of the information.
3. Motivate students to persist in
higher level petrographic studies as well as career path toward
petroleum and service industries.
How To Use The Tutorial
The principle subdivisions of the
tutorial are based on the major ‘clans’ of the Folk sandstone
classification: quartzarenite, arkose, litharenite (Folk,
1974), and a fourth group of sandstones that do not fit within this
standard scheme (Figure
1). For each of these clans there are images that deal principally
with provenance and those that are primarily instructive about
diagenesis (Figure
2). Within each of the four major subsections the user has the
option to review text outlining the principal facts and themes conveyed
by the subsection (Figure
2, “Goals”) and to proceed through the tutorial images one at a time
(Figure
2, “Tutorial”), in the order they are arranged. Alternatively, all
the images within a subsection can be reviewed in a thumbnail section (Figure
2, “Browse”;
Figure 3), which allows the user to navigate to a full-frame image
at any point within the tutorial. Once the user is in one of the main
tutorials, general information on the specimen can be retrieved from the
“Info” button on the function bar (Figure
4). Active regions of the image are indicated when the cursor
changes from an arrow to a pointing hand. Clicking on such a region
calls up information (Figure
5) in one of two modes. In the first, a click brings up a short
identification of the
activated region, a tiny bit of text
that quickly disappears on its own. Clicking on the region related to
the major theme of the image retrieves a larger box of text. The user
then clicks anywhere on the image or function bar to remove this textbox
and proceed with his/her explorations. Holding a click
on an active region allows the
user to get a leisurely look at the mapped area relevant to the textbox.
An online glossary is provided by a hyper-linked textbox, which appears
in orange color with underline (Figure
5). Navigation to sequentially positioned images within tutorial
subsections is accomplished with arrow buttons on the function bar.
Plane light and cross-polar views can be toggled with “PPL/XPL” button
on the function bar (Figure
6 and
Figure 7). In some cases plane light and cross-polar views are
mapped somewhat differently, and clicking on the same regions in these
different imaging modes may activate different informational boxes. The
“History” button allows the user to create a sequential record of pages
visited in their path through the tutorial; double-clicking on any page
in this list allows the user to return to that point in the user’s trek
(Figure
8). The “Search” button allows the user to generate a list of pages
featuring an image or text relating to a particular topic; it therefore
turns the digital tutorial into a powerful petrographic image database (Figure
9). A user could always go back and consult the tutorial either on
CD, or eventually online, to freshen his/her mind regarding a particular
type of grain and feature.
Return
to top.
Ongoing Activities And Future Plan
The demonstration version of the
tutorial described here is presently being evaluated in laboratory
exercises in an undergraduate-level sedimentary rocks course at the
University of Texas at Austin. A proposal currently in development
will seek to expand the tutorial content and extend the evaluation
process to other universities. Plans for future tutorial content
include: specific examples from well-known sandstone reservoirs;
inclusion of more petrographic features that play a significant role in
reservoir quality (e.g., an expanded section on clay cements);
utilization of a wider variety of petrographic image types (for example,
scanning electron and cathodoluminescence micrographs); quiz functions;
greater graphical content in the compaction and texture sub-tutorials.
Our long-term goal is linking teaching modules for sandstones and other
rocks to a major archive of images from the
University of Texas at Austin petrology collections. In fully
realized form, this digital library may ultimately have undergraduate-,
graduate-, and research-level interfaces.
Acknowledgements
Support
for the development of this tutorial has been provided by the
College of Natural Sciences, the
University of Texas at Austin through student-funded technology
fees, and the
National Science Foundation,
Division of Undergraduate Education,
Course Curriculum and Laboratory Improvement Program; under grant
#DUE-0088763. We thank Drs. Kathie Marsaglia, Shirley Dutton, Ted
Walker, and Robert Folk for reviewing the tutorial in its early stages.
Luis Crespo and Petro Papazis provided assistance for image mapping.
Return
to top.
References
Carozzi, A.V., 1996, Carbonate petrography: grains,
textures, and case studies, in Scholle, P.A. and James, N.P.
(eds.), SEPM Photo CD, Volume 9: Tulsa, Oklahoma, SEPM.
Christiansen, E.H., 2001, PetroGlyph 1.0 Multimedia
CD-ROM: Malden, Maryland, Blackwell Science.
Folk, R.L., 1974, Petrology of sedimentary rocks: Austin,
Texas, Hemphill Publishing, 184 p.
Lander, R.H., and Walderhaug, O., 1999, Predicting
porosity through simulating sandstone compaction and quartz cementation:
AAPG Bulletin, v.83, p.433-449.
Thomasson, M.R., 2000, Rocks are still key exploration
clues: AAPG Explorer, v.21, p.4, 13.
Walderhaug, O., 2000, Modeling quartz cementation and
porosity in Middle Jurassic Brent Group sandstones of the Kvitebjorn
Field, northern North Sea: AAPG Bulletin, v.84, p.1325-1339.
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Table 1.
Examples of petrographic educational materials on the World Wide
Web. These materials demonstrate the capabilities of digital media for
presenting petrographic information. None of the sites, however, contain
sufficient interpretive content or adequate numbers of siliciclastic
samples to serve as a comprehensive resource for undergraduate-level
petrographic instruction in siliciclastic petrology.
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1.
http://www.geolab.unc.edu/Petunia/IgMetAtlas/mainmenu.html Atlas of
igneous and metamorphic rocks, minerals, and textures. An atlas site
with thin section photomicrographs and descriptions of 39 minerals, 20
plutonic textures, 14 volcanic textures, and 21 metamorphic textures.
The user can switch between plane-polarized light and cross-polarized
light view in selected images.
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2.
http://sorrel.humboldt.edu/~jdl1/petrography.page.html A tutorial
with extensive image collection. Mostly in x-polars. Limited
interpretive material. Images presented at less than screen size.
Presented at the introductory (non-major) level.
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3.
http://mccoy.lib.siu.edu/projects/crelling2/atlas/ Atlas of 231
photomicrographs of coals, cokes, chars, carbons, and graphite.
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4.
http://www.science.ubc.ca/~eoswr/cgi-bin/db_minerals/search.cgi 28
minerals in thin sections with their physical properties and diagnostic
features.
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5.
http://www.brocku.ca/earthsciences/people/gfinn/minerals/database.htm
Images of 27 minerals in plane light and x-polars along with
crystallographic, optical, and chemical, and occurrence information. A
digital version of a traditional mineralogy book.
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6.
http://www.gly.bris.ac.uk/www/teach/opmin/mins.html#menu Minerals
under the microscope tutorial, though actual petrographic images are
limited and not interactive; along the lines of an online textbook.
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7.
http://www.hia.net/kjsmith/minerals/min0.htm
9 photomicrographs of minerals and metamorphic rocks with short
descriptions.
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8.
http://micro.magnet.fsu.edu/primer/virtual/virtualpolarized.html
Interactive Java tutorial of polarized light microscopy. Good
information on general microscopy.
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9.
http://geologyindy.byu.edu/Petroglyph/default.htm Demo page of the
PetroGlype 1.0, a virtual microscope that simulates the features of
optical and electron microscopes.
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10.
http://exodus.open.ac.uk/earth/virtual_mic/virtual_microscope.html
Demo version of the Digital Microscope. Images are presented in
interactive (i.e., 360 degree rotatable) plane polarized and
cross-polarized versions.
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to top.
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