Chapter 2

Structural Mapping Techniques and Tools

In Chapter 2 we ‘find our bearings’ in order to locate outcrops in the field and construct maps of geological structures. 

Geographic coordinates are used by the Global Positioning System (GPS) for location and the Universal Transverse Mercator (UTM) projection is used to project geographic information from Earth's curved surface onto a piece of paper. We describe a modern mapping campaign that utilized GPS technology to create a precise structure contour map in a region where four sets of faults intersect to disrupt and fold the surrounding strata. The mapping was accomplished in a fraction of the time and with much greater control than previously possible. We anticipate a new generation of structural maps that will provide the impetus for more specific modeling of tectonic processes and the data to better constrain those models.

Downloadable supplementary materials available at the Cambridge University Press website for the textbook include exercises for students in WORD and PDF format, solutions for instructors in WORD and PDF format, all the images from the text in JPG format for classroom usage, and MATLAB .m scripts for the exercises.

Exercises

Concepts from Chapter 2

These exercises explore concepts from Chapter 2 including the gnomonic and Mercator projections, 2- and 3-dimensional transformation of coordinates, and use of the equal angle stereonet to plot the orientations of planar and linear structural elements.

Mapping dikes at Ship Rock

This exercise introduces the position vector for mapping geological contacts and the translation and rotation of a local coordinate system to a map with standardized coordinates. The thickness variations along a dike also are examined to investigate physical mechanisms operating during emplacement of the magma.

Mapping faults at Chimney Rock

In this exercise we consider basic concepts and tools for mapping geological structures and for analyzing the orientations of linear and planar structural elements. Both structural maps and stereographic projections are prepared using ten data sets for faults from Chimney Rock, Utah. The spherical variance is used to evaluate the clustering of orientation data.

Kinematics of faulting at Chimney Rock

The kinematics of faulting are examined at Chimney Rock, Utah. Slickenlines on exposed fault surfaces are used to analyze the direction of slip and to investigate how these directions vary along a fault. Structure contours are constructed from GPS data for the Carmel and Navajo formations and these are used to identify faults and to measure the magnitude of slip.