. Bulletin of the Geological Society of America. Geology. SQUARE BUTTE. 401 to the Colorado group of the Cretaceous period. In the vicinity of the butte this tableland is deeply trenched by the Arrow river and its tribu- tary streams, and in consequence it forms locally a broken country, affording excellent geologic sections and typical '* badlands " scenery. At the base of the butte three intrusive sheets of the dark igneous rock mentioned by Lindgren occur in these sediments. Above this flat, trenched tableland the butte rises abruptly to a height of 1,700 feet above its pediment. The s


. Bulletin of the Geological Society of America. Geology. SQUARE BUTTE. 401 to the Colorado group of the Cretaceous period. In the vicinity of the butte this tableland is deeply trenched by the Arrow river and its tribu- tary streams, and in consequence it forms locally a broken country, affording excellent geologic sections and typical '* badlands " scenery. At the base of the butte three intrusive sheets of the dark igneous rock mentioned by Lindgren occur in these sediments. Above this flat, trenched tableland the butte rises abruptly to a height of 1,700 feet above its pediment. The slopes, at first gentle, change quickly to steeper declivities and terminate at the top, on all sides, by a precip- itous wall several hundred feet high. Only in a few places is this escarp- ment cut by very small, narrow gulches, which permit difficult ascent to the top. The summit is a nearly level area, elliptic in outline and nearly one mile across in its greatest length. It is largely covered by a dense growth of small pine, with occasional park-like glades and m njfM Figure 3. — View of Square Butte from the Slopes of Palisade Butte. The quite symmetric form of the butte is rather remarkable. It pre- sents from nearly every point the appearance of a very short section of a huge cylinder resting on a low, broad, truncated cone. This regular arrangement is interrupted only on the southwest side, where a short tongue-like protrusion of the mass occurs. The facts which have been stated are shown on the map accompanying the previous article (page 393), while they are presented in greater detail on a larger scale in figure 4 of the present paper. Figure 3 gives also a view of the butte from Pali- sade butte and shows well the tongue-like protrusion. ITS LACCOLITIC ORIGIN. A careful examination of the butte shows that it is composed entirely of igneous rock. Above the sandstones of the tableland no sedimentary. Please note that these images are extracted from scanned


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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890