Table Of ContentTable of Contents
Cover
Title Page
Copyright
About the Author
Preface
Chapter 1: Introduction
1.1 Why Do We Need Drawings?
1.2 The Tools
1.3 Sizes of Drawings
1.4 Geological Versus Artistic Drawing
1.5 Drawing With Symbols
1.6 Realistic Drawing
1.7 The Fractal Geometry of Geological Fabrics
1.8 Basic Rules of Geological Drawing
References
Chapter 2: Rock Thin Sections
2.1 Drawing as a Form of Microscopy
2.2 Drawing with Various Tools
2.3 Foundations of Thin-Section Drawing
2.4 Minerals and Their Characteristic Fabrics Under the
Microscope
2.5 Sketches for Fast Documentation
2.6 Development of Precise Thin-Section Drawings
2.7 Digital Reworking of Manual Thin-Section Drawings
2.8 Digital Drawing
2.9 Summary
References
Chapter 3: Specimen Sections
3.1 The Geological Message of a Drawing
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3.2 Schematic Representation of Minerals
3.3 Schematizing Rocks and their Structures
3.4 Development of Drawings
3.5 Illustration on Different Scales
3.6 Detailed Drawings of Sample Cuts
3.7 Summary
Chapter 4: Drawing Rock Structures in Three Dimensions
4.1 Foundations
4.2 The Development of Schematic 3D Drawings
4.3 Field Drawing
4.4 Digital Processing
4.5 Rules of Labeling
4.6 Summary
References
Chapter 5: Geological Stereograms
5.1 Foundations
5.2 Orientation and Extension
5.3 Additions and Labeling
5.4 Digital Processing
5.5 Summary
References
Chapter 6: Solutions
Index
End User License Agreement
List of Illustrations
Chapter 1: Introduction
Figure 1.1 One of the author's early, but failed, attempts to
draw samples and outcrops in the field, and a better version
of the same drawing. (a) Monoclinic fold in psammopelite
and quartzite layers of the Moinian (Grampian Highlands
at Loch Leven, Scotland); field drawing; outcrop KR513;
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field book 6 (Kruhl, 1973). The drawing contains numerous
shortcomings; above all, imprecise layout of lines, a sloppy
perspective, and an incorrect positioning of foliation planes
in the metapsammopelitic layers. (b) The same drawing
redrawn years later. Cross bedding and S1 foliation planes
are more precisely placed; the perspective is correct and,
consequently, the 3D appearance of the drawing is better;
the carbonate spots are more realistically illustrated; and
the labeling is more closely related to the structures. Circles
L and K indicate positions of samples. Both drawings ca.
A6; black ballpoint pen.
Figure 1.2 Drawing of part of the Grand Canyon, “Vishnu's
Temple” (Dutton, 1882, plate XXXIV): a felicitous
combination of artistic, geological, and geomorphological
representation.
Figure 1.3 (a) Photo of the “Spitznack” Fold (near the
Loreley, Middle-Rhine region, Rhenish Massif, Germany).
Centimeter- to decimeter-thick metapsammopelitic layers
are bent to an open, monoclinic fold. The boundaries of
bedding are represented by strong fractures in the
horizontal fold limb and by weak fractures and differences
in brightness in the vertical limb. In addition, a schistosity
can be recognized. It is represented by narrow-spaced,
nearly parallel fractures. The schistosity is pronounced and
steep in the horizontal limb, fan-shaped in the fold crest,
and is barely visible in the steep limb. Additional fabric
details cannot be recognized. Hammer as scale. (b)
Schematic drawing of the same fold. Based on the small
protrusions and the fabrics that can be recognized on them,
the planar, 2D view has been supplemented to form a 3D
block. Highlighted are (i) the partitioning of the schistosity
to two different sets of foliation planes in metapsammitic
layers, (ii) the pile shape of the schistosity in metapelitic
layers, (iii) the stretching lineation on an obviously
bedding-parallel foliation plane, (iv) the compressed and
sheared quartz veins in the steep limb, and (v) the
slickensides on steep bedding-parallel shear planes. All
these structures are not visible in the photo and are only
revealed by close observation of the fold. Modified after
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Zurru and Kruhl (2000, Figure 33); size of original drawing
ca. B4. A more comprehensive drawing is shown in Figure
4.27.
Figure 1.4 Six well-known droodles. Together with other
ones, they can be easily found in the internet. (a) Cat that
peers into a mousehole; (b) giraffe standing in front of a
window; (c) bear climbing a tree; (d) person with a large
sun hat on a bicycle; (e) four elephants nosing at a ping-
pong ball; (f) chessboard for beginners.
Figure 1.5 Geological 2D pictograms ranging from kilometer
to decimeter scale, reduced to the essentials. (a)
Detachment; (b) metamorphic core complex; (c) strike-slip
fault that displaces two halves of a granite pluton; (d)
stratovolcano; (d) pillow lava; (f) cross-bedding.
Figure 1.6 Pictogram of a meteorite impact; redrawn
symbol from a sign-board of the geopark “Nördlinger Ries”
(Germany).
Figure 1.7 Schematic representation of rock fabrics. (a)
Granitic (top) and volcanic vein (bottom) in a layered
gneiss. Crosses represent feldspar cleavage planes in
granite. “v” stands for volcanic rock. The homogeneous
distribution of symbols represents the homogeneity of the
rock fabric. (b) Orthogneiss layer in schist. The “wave” ∼
symbolizes the wavy structure of the gneiss, which
originates from the lenticular shapes of deformed feldspars
and the distribution of the surrounding biotite flakes. The
schematized fabric includes the information that the gneiss
was deformed at temperatures high enough for crystal-
plastic deformation of feldspar. The parallel lines represent
the foliation in the schist. In addition, they contribute to the
light-dark contrast that typically exists between orthogneiss
and schist. (c) Bedded limestone. The cross-strokes
symbolize fractures that form perpendicular to bedding
during diagenesis and compaction and are rarely present in
other rocks in such formation. (d) Folded limestone layer
with schematized fabric adapted to the form. The cross-
fractures were formed prior to folding and, consequently,
remain perpendicular to the layering after folding. Watch
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out! This is an interpretation that needs to be supported by
observation. Fractures generated during or subsequently to
folding can be oriented differently. (e) Folded limestone
layer with schematized fabric not adapted to the form.
Geometry of the fold and orientation of the schematized
fabric communicate different messages. Their contrast may
confuse viewers. (f) Boudinaged layer. Solid and broken
lines represent foliation planes, which are curved as a result
of boudinage. The light-dark contrast emphasizes layers of
different composition. In general, the impression is
generated that a strong gneiss layer is boudinaged in a
mantle of weak schist. (g) The computer-generated gray-
white gradation preserves the “correct” light-dark contrast;
however, the foliation geometry cannot be represented.
Figure 1.8 Complex (fractal) geological structures. (a)
Devonian metapsammopelite with bedding of variable
thickness; Hartland Quay (Devon, England). (b) Fe-Mn
dendrites on a bedding plane of “Plattenkalk” (Solnhofen,
Germany). The dendritic pattern is similar on different
scales. (c) Fracture pattern on a block cut of Malm
limestone; sample KR5149B; Unterwilfingen Quarry
(Nördlinger Ries, Germany). The fractures are clustered,
that is, form few large and many small fragments. The size
distribution of these fragments follows the power law. (d)
Photomicrograph of a sutured quartz grain boundary;
sample KR4846B; syntectonically crystallized tonalite
(Abbartello, Golfo de Valinco, Corsica, France). The
geometrical arrangement of the few large and many small
sutures follows the power law.
Figure 1.9 Sketch of a folded rock layer with two different
types of schematized lineations: (a) variably long and
evenly distributed strokes; (b) variably long and clustered
strokes. Sketch (a) looks artificial, in contrast to sketch (b).
Figure 1.10 Schematic distribution (flow) pattern of feldspar
phenocrysts in a porphyritic granitoid. (a) Crystals of equal
size with equal orientation and spacing. (b) Crystals of
different size but with equal orientation and nearly equal
spacing. (c) Crystals of different size (few large, many
small crystals) with slightly different orientations and
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clearly different spacing (clustering).
Chapter 2: Rock Thin Sections
Figure 2.1 Crystal shapes and characteristic sections of some
rock-forming minerals. In addition to the 3D form,
transverse and longitudinal sections, as well as an arbitrary
section, are shown. 3D forms modified after Tröger et al.
(1979); see text for details.
Figure 2.2 Schematic illustrations of important rock-
forming minerals with characteristic shapes and internal
fabrics as observed in thin section. For each mineral, the
range of refractive indices, n (after Tröger et al., 1979), and
the resulting approximate range of line weights are
specified. The line weights relate to sketch sizes of ca. A5 to
A4. Black bars represent 1 cm in the original sketch.
Characteristic internal fabrics should be used specifically in
schematic sketches. The illustrated ones represent selected
examples and by far do not cover the entire range of
potential fabrics.
Figure 2.3 Greenschist-facies orthogneiss from the eastern
Tauern Window (Eastern Alps, Austria); sample KR2916A;
mineralogical composition: quartz (Qtz), plagioclase (Pl),
biotite (Bt), chlorite (Chl) and epidote (Ep); pencil drawing
based on a microscope image in plane-polarized light; size
of original drawing ca. A4; line weight 0.5 mm and locally
lighter, due to obliquely set lead. The drawing develops
successively. (a) Contouring of the larger mineral grains
and the epidote layer with the same light line weight for
easier correction. The end faces of the biotite platelets are
sketched straight, indicating the magmatic origin of the
crystals. (b) Intensification of contours and internal fabrics
in plagioclase and biotite. Saussuritization (sauss) in
plagioclase is schematized for the purpose of saving of time.
The grain margin, poor in saussurite, is highlighted,
because it reflects a magmatic zoning and, consequently, the
magmatic origin of the crystals. (c) Finalization of the
drawing by labeling, filling the epidote layer, drawing of
the quartz subgrain boundaries, and adding the second
(incomplete) epidote layer that was missing before. This
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relatively cursory sketch serves to illustrate the
characteristics of rock deformation: (i) an early magmatic
to sub-magmatic deformation, which led to foliation (S1:
shape orientation of biotite, plagioclase and coarsely
sutured quartz) and local recrystallization of plagioclase,
and (ii) a subsequent brittle deformation that generated
epidote-filled fractures (S2) oblique to S1.
Figure 2.4 Amphibolite-facies gneiss (Scheelite deposit
Mittersill, Tauern Window, Eastern Alps, Austria); sample
KR3768B; mineralogical composition: quartz (Qtz),
amphibole (Am), biotite (Bt), chlorite (Chl), apatite (Ap) and
scheelite (Tu); pencil drawing based on a microscope image
in plane-polarized light; line weight 0.5 mm and locally
lighter, due to obliquely set lead; original size of a single
sketch ca. A4. The drawing develops successively. (a)
Contouring of quartz areas in order to outline the layering
and the grain distribution of other minerals; contours in
light line weight for easier correction. (b) Intensification of
contours and fillings according to the difference in
refraction between quartz and other minerals. (c)
Contouring within quartz areas with light line weight. (d)
Complete filling of grains with high refraction, specifically
of amphibole (with characteristic angle between cleavage
planes) and scheelite; completion of grain boundaries in the
amphibole layer (based on a microscope image with
crossed-polarized light) and labeling. Grain boundaries in
the scheelite areas illustrate the partitioning to larger
grains with irregular shape and smaller isometric ones and
thereby indicate the recrystallization of scheelite.
Figure 2.5 Metasomatically overprinted conglomerate;
Mary Kathleen Mine (Mt. Isa Inlier, Australia); sample
KR5090D; mineralogical composition: K-feldspar (Kf),
plagioclase (Pl), clinopyroxene (Cpx), epidote (Ep), apatite
(Ap) and zircon (Zr); three pencil drawings based on
microscope images in plane-polarized light; original size of
sketch assembly ca. A4; development in two steps. (a)
Contouring of all grains with the same line weight and
labeling. (b) Intensification of grain outlines and
characteristic internal fabrics: twin lamellae in plagioclase,
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diffuse gridiron (microcline) twinning in K-feldspar, and
cleavage planes in clinopyroxene. These internal fabrics are
schematized, that is, represent the real fabrics only roughly
but characterize the minerals. The line weight of the
boundaries between pyroxene and other minerals of lower
refraction is increased, in contrast to the line weight of
internal boundaries.
Figure 2.6 Amphibolite-facies andalusite schist (Sesia Zone,
Western Alps, Val Loana, Northern Italy); sample KR1481;
mineralogical composition: quartz, white mica, biotite,
andalusite, staurolite and ore (opaque); pencil drawing
based on microscope image in plane-polarized light;
original size of drawing ca. A4. Biotite and white mica show
outlines with similar line weights and cleavage planes
typically pronounced close to the end faces of the thin
tabular crystals. The brown, inherent color of biotite is
represented by fine dotting, however, without considering
the (meaningless) different intensity of color due to
pleochroism. In comparison to mica, the sutured quartz
grain boundaries, with their straight facets, are drawn with
lighter line weight. The few subgrain boundaries are drawn
as dotted lines. Based on the relatively high refraction of
staurolite, the three small rounded grains (St) are
silhouetted against the surrounding grain fabric by thick
grain boundary lines and thick internal dotting.
Figure 2.7 Garnet-albite schist from the garnet zone of
Barrow metamorphism (Dalradian of the Scottish
Highlands; Power Station Ardlin, Loch Lomond, Scotland);
sample KR1434; mineralogical composition: quartz (Qtz),
albite (Ab), white mica, biotite, garnet, epidote (Ep), apatite
(Ap) and ore (opaque); free-hand ballpoint pen drawing of
thin-section image in plane-polarized light; variation of line
weight through different pressure on the ballpoint pen; size
of original drawing ca. A5. Garnet, epidote, and apatite
grains serve as initial “support points.” Subsequently, mica
and albite grains are drawn and, finally, quartz and the
inclusions in albite. In order to save time, the drawing is
kept incomplete. Biotite and white mica show the same line
weight but can be distinguished by internal dotting of
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biotite. Apatite (Ap) and epidote (Ep) differ from their
albite-white mica surroundings by heavier line weight and
from each other by different dotting that mimics the
different refraction of the two minerals.
Figure 2.8 Breccia of the Zuccale Fault (Punta di Zuccale,
Elba, Italy); sample ZV13a; mineralogical composition:
quartz (Qtz) and calcite (Cc); pencil drawing of a thin-
section image in plane-polarized light; size of original
drawing A4. The drawing develops successively. (a)
Contouring of the larger quartz and calcite areas, in order
to outline the layering and record proportions and
distribution of the crystals. In addition, (i) the position of the
structure in thin section, (ii) the orientation of the thin
section in relation to the sample and to the lineation
(“striation”), and (iii) the orientation of the sample in
relation to the fault (“bottom”) are indicated. (b) Increasing
of line weight of the palisade-quartz–calcite boundaries and
drawing of fillings and small structures. (c) Drawing of (i)
fine-grained areas, (ii) fluid inclusions (FI—only locally for
saving time), and (iii) an enlarged section (A) for better
visualization of fluid inclusions. Labeling and indication of
dominant quartz-c orientations and the supposed shear
sense.
Figure 2.9 Metagabbro of the Finero Complex (Ivrea Zone,
Southern Alps; Valle Cannobina, Northern Italy), deformed
under amphibolite-facies conditions; sample KR740;
mineralogical composition: garnet (Grt), clinopyroxene
(Cpx), amphibole (Am), plagioclase (Pl), apatite (Ap), and
ore (opaque); original size of the drawing ca. A4. (a) Pencil
drawing of a thin-section image in plane-polarized light; all
grain outlines and internal fabrics are drawn with equal
line weight; minerals are labeled and marked by hatching
and internal fabrics; ore grains are outlined in black. (b)
Drawing finalized with ink pen. The high relief of garnet is
represented by line weight 0.5 mm and dotting along the
grain boundary; the high chagrin by thick internal dotting
(line weight: 0.5 mm). The outlines of pyroxene and
amphibole grains are drawn with line weight 0.35 mm. The
closely spaced parallel lines in spotted areas represent fine
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