Drawing Geological Structures

Even though visual recording is dominated nowadays by graphic computer programs and the digital camera, manual drawing of geological structures is not a luxury but a necessity. Drawings prove their strength where computer–generated sketches and photographs fail: They serve for quick and simple documentation in the field or at the microscope. They leave out, emphasize and document the main features while the camera only provides a large data salad . They have a language of their own which can be applied where necessary and which can be flexibly adapted to the requirements of documentation and representation, and they can combine information and arrange information in relation to specific needs. Last but not least, making drawings raises the quality of observation and contributes to the understanding of geological structures and the structure–forming processes. Geological drawing is assisted scientific thinking.

1.1 Why we need drawings of geological structures: sketch vs photograph and linguistic presentation, sketches as means of transport for geological information; documentation and recording of data; from 2d to 3d; drawing as a way of thinking.

1.2 Aids: paper and pen; advantage and disadvantage of computer drawing programs.

1.3 Geological vs artistic drawing: characteristics of geological drawing; observation and drawing; schematic vs exact drawing; balance between exactness and symbols.

1.4 Symbolic drawing: symbols in daily life (pictograms, droodles , hieroglyphics, development of letters from symbols, complex pictograms in geology, transition from pictogram to schematic sketch, signatures.

1.5 Realistic drawing: the movement of the hand, concentration and tension, interpretative drawing.

1.6 Exercises.

2. Thin sections (∼30 printed pages, including ∼30 figures) .

2.1 Making sketches a way to microscope and support our way of observing.

2.2 Aids.

2.3 Basics of thin–section sketches.

2.3.1 The thin section a 2d section across a 3d fabric.

2.3.2 Special mineral properties.

2.3.3 Scale–dependent presentations.

2.4 Minerals and characteristic fabrics in thin section.

2.4.1 Characteristic 2d shapes of rock–forming minerals.

2.4.2 Mineral identification by internal fabrics.

2.4.3 Schematic representation of reaction and deformation fabrics.

2.5 Development of schematic thin–section sketches.

2.6 Computer–based revision of thin–section sketches.

2.7 Thin section sketches for quick documentation and overview.

2.8 Examples of documentation sketches.

2.9 Exercises.

3. Sample sections (∼25 printed pages, including ∼20 figures) .

3.1 Rocks signatures vs half–schematic vs realistic drawings.

3.1.1 The geological message of the drawing.

3.1.2 Representation of different rock types in different scales.

3.1.3 Scale–dependent sketches of minerals and structures.

3.1.4 Characteristic cut figures of minerals.

3.2 Schematization of rock structures.

3.2.1 The fractality of structures.

3.2.2 Computer–based revision von sample sections.

3.3 Sketching in the field.

3.4 Comparison drawing – photograph.

3.5 Examples of sample–section drawings with explanations.

3.6 Exercises.

4. Samples (∼30 printed pages, including ∼25 figures) .

4.1 Basics: size of sketches, shape, orientation, structures in 3d.

4.2 Development of schematic 3d–drawings.

4.3 The freedom of composition: arrangement of structures.

4.4 The geological message of a sketch.

4.5 Rules of labelling.

4.6 The final sketch in comparison to the fieldbook sketch.

4.7 Examples of sample drawings with explanations.

4.8 Exercises.

5. Block diagrams (∼20 printed pages, including 20 figures) .

5.1 Basics: advantages and limitations, orientation and composition.

5.2 Block diagrams with additional datasets.

5.3 Abstract vs half–schematic block diagrams.

5.4 Step–wise development of block diagrams.

5.5 Examples of block diagrams with explanation.

5.6 Exercises.

6. Geological landscapes (∼15 printed pages, including ∼10 figures) .

6.1 From photograph to sketch to geological drawing.

6.2 Geological landscapes as block diagrams.

6.3 Examples of geological landscape drawings with explanations.

6.4 Exercises.

7. References .

8. Solutions of exercises .

Estimate of the overall length and number of figures:.

∼ 150 printed pages in total, including ∼ 115 figures.

Examples of drawings: .

Fig. 2.15: Development of thin–section sketch (high–T garnet–quartz–feldspar mylonite, Ivrea Zone).

Fig. 2.22: Development of thin–section sketch (metagabbro, Finero Complex, Southern Alps)

Tectonics and Material Fabrics Section, Technische Universität München, Germany