The use of stereographic projection in structural geology / Использование стереографической проекции в структурной геологии

Many of the problems which arise during a study in structural geology are essentially exercises in three-dimensional geometry. Data acquired from field-observations—strike and dip of planes (beddingplanes, planes of schistosity or cleavage, faults, etc.), the pitch and plunge of lineations (outcrops, slickensides, micro-folds, flow-lines, elongation of mineral components or of inclusions, etc.) and all other related vector data are incorporated in a geological map and in accompanying illustrative sections. Both in the construction of such sections and ofrelated block-diagrams, and in the further study of the structural features of an area, it is frequently necessary to make various calculations. Sometimes, indeed, as in many of the problems of mining geology and in the interpretation of borehole cores, the necessity for calculation arises at an even earlier stage, since such fundamentals as the dip and strike of a bedded series are only indirectly derived from the observed data.<...>