Dixon, and 5 co-authors reported in 2014 that structural analysis proceeds through three linear stages:
1) description of the structural geometry of a deformed field area (bedding attitudes, planar fabrics, linear fabrics, folds, faults, joints, etc.);
2) kinematic analysis (movements responsible for the development of structures [translation, rotation, distortion, and dilation] and relative timing); and
3) dynamic analysis (interpretation of forces and stresses responsible for the deformation). Stage 1, descriptive structural analysis, is the product of careful field mapping.
Although maps are two-dimensional sheets of paper, they portray the geology in three-dimensions. This is because most structures tend to dip or plunge and, therefore, one can infer the direction and degree of dip or plunge through outcrop patterns. Also, we use special geologic symbols to indicate 3-dimensionality on our maps. Therefore, a geologic map is nothing more than the representation of 3-d structures on an arbitrary 2-d horizontal plane. Put another way, a geologic map is a cross-section of dipping and plunging structures projected on a horizontal plane. Clearly, it is necessary to carefully map out this 2-d view before one can visualize the 3-d geometry of deformed rocks. A well-done geologic map can provide a powerful down-plunge view of the 3-d structural geometry in a “true” cross-section view that is to plunge.
Field mapping can be physically and mentally challenging. Hundreds of questions arise, dictating that hundreds of decisions must be made during the course of a single day. Where should I go? What unit is this? Why does this bed abruptly end? Thus, field mapping is the ultimate application of the scientific method – a good field mapper is constantly testing predictions about the next outcrop and evaluating multiple hypotheses about the structure. In the midst of this mental workout, it is important to maintain your focus and purpose by remembering the goals of your project or research.
Try to maintain a good sense of humor and enjoy the day. After all, didn’t most of us decide to go into geology because we like being outdoors and we like thinking about the Earth?
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