Analysis of 1:48,000-scale thematic mapper (TM) imagery of a portion of the Raton basin, supplemented with 1:80,000-scale black and white stereo aerial photographs and geologic and topographic maps, shows that many more dikes are present in the basin than are shown on previously published maps. In comparison with the geologic map, this study allowed mapping of a greater number of dikes, and extension, or connection, on refinement of the trend and/or location of many previously mapped dikes. Only a small number of dikes (or portions of dikes) were mapped in the field by previous investigators, for which no evidence was shown on TM imagery, aerial photography, or topographic maps.

Comparison of the TM imagery with the aerial photography reveals that TM imagery may be a better tool for locating dikes. Clearly, smaller objects can be identified and greater detail can be mapped using aerial photography as compared with TM imagery. For example, the photography

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clearly shows that several dikes are right-laterally offset. These offsets appear on TM imagery only as subtle bends, rather than breaks in the dikes. However, because TM imagery reveals subtle spectral differences that aerial photography cannot, the imagery will display more information. This is demonstrated by nearly twice the number of dikes being mapped using TM imagery than with aerial photos.

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