Guidelines for identifying igneous and metamorphic rocks from aerial photographs in the northern half of the Cordillera Central
DOI:
https://doi.org/10.32685/0120-1425/bolgeol17.1-3.1969.425Keywords:
Colombia, guide, structural features, drainage characteristics, textural features
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Abstract
With quick but rational field checks, a thorough study of aerial photographs can be of invaluable assistance in conventional geological work.
Recognition criteria such as drainage features, structural features, photographic tone, textural features, shape, vegetation, and erosional features or topographic expression are used to recognize different rock types from aerial photographs. Combining two or more criteria makes it possible to identify many rock types or group them into representative units. For each area, a certain recognition element or elements can be diagnostically useful for a certain rock type or unit.
All those guidelines and criteria for identifying and separating different types or units of rocks from aerial photographs are presented, and special emphasis is given to igneous and metamorphic rocks. Stratified sedimentary rocks and recent Quaternary deposits are treated in a generalized way.
In the studied area, drainage and structural features have been the most valuable identification criteria and in secondary order, vegetation, and tone.
Examples of each group or special type of rocks are presented in the first part and in the second part of geologically complex areas where more than two units’ outcrop.
The drainage schemes were drawn directly from the photographs at random, and each covers an area of approximately 15 square kilometers.
This report uses aerial photographs at an approximate scale of 1:55,000 from the Agustín Codazzi Geographic Institute.
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