Geology

One of the objectives of studying a complexly deformed area (e.g., refolded folds) is to identify domains (subareas) within which the fabric data of, for example, folds, lineations, foliations are homogeneous. This means, for example, that the hingelines and/or fold axes, and the poles to the axial planes (or axial planar foliation, if it exists) of all minor folds define maxima (i.e., cluster distribution), with the mean axis lying on the mean axial plane. The boundaries of the domains are identified (mapped) by locating the adjacent stations at which specific fabric data are homogeneous. The homogeneity in each domain reflects two major facts: (1) Homogeneity of the strain which results in equal extension in a strain field in which the axes of the maximum principal extension are parallel at every point, keeping originally-parallel lines and planes parallel, and straight lines straight. (2) Homogeneity of the rock, i.e., rock properties is the same at each point in the rock continuum during the deformation. Geologists cannot produce a useful map of, or obtain useful information from, moderately- to highly-deformed areas, without knowing how to use the compass to collect the fabric data and to delineate the domain boundaries. Thus, we need to know how to measure linear and planar objects of all kinds, such as sedimentological and structural fabric elements, and map lithostratigraphic boundaries such as contacts.