A COAL-MEASURE FOREST 241 



the topography. When the top of the Sandia formation is reached, 

 the topography changes, and the country rises in abrupt escarp- 

 ments of massive to earthy Hmestone of the characteristic Upper 

 Coal-Measure habitus. At the base, this formation is locally very 

 fossiliferous with the well-known Coal-Measure assemblage, a partial 

 list of which will be given below. 



The first escarpment may rise some 100 to 150 feet, and is followed 

 by others of the same character, indicating a probable aggregate 

 thickness of 300 to 500 feet. The continuity of the section is here 

 broken by what may be called the "Cane Spring monocline" or fault 

 zone. This will be more particularly described later on, and it will 

 here be noted that this break forms in effect a rough delimitation of 

 the Carboniferous from the so-called Permian. To the east of this 

 the hills are mostly composed of earthy limestones, with shales of 

 prevailingly reddish color, with gypsum beds and calcium anhydrite 

 deposits to the base of the great escarpment forming the sky-line to 

 the spectator from the west side of the river at Socorro. This ridge, 

 which is the southern continuation of the Cibolo (Seboyo) Mountains, 

 consists of from 500 to 600 feet of red beds, with gypsum and anhy- 

 drite inclusions, capped by 150 to 175 feet of yellowish sandstone and 

 100 to 200 feet of gray, massive, non-fossiliferous limestone, with at 

 least one small band of quartzite. Still to the eastward are hills 

 containing the typical upper red-bed formations. To the south this 

 whole series disappears beneath the Carthage coal fields of Cre- 

 taceous age. 



To return to the plant beds, it will be noted that the fire clay, 

 with its attendant shales, reposes directly upon the granite, or with a 

 thin layer of quartzite between. The clay is of good quality, but very 

 irregular, and has formed the base of the fire brick manufactured by 

 the Socorro Fire Clay Co. In the clay, and especially in the shales 

 overlying, are the remains of lepidodendrids and other coal plants 

 referred to. A thin seam of coal is apparently present, though at the 

 time of our inspection there was no opportunity to discover it in place. 

 Report affirms that a boring one and one-half miles south encountered 

 two small coal seams within 200 feet. 



' The thickness of the clay and attendant shales is not over 30 feet, 

 of which half may be roughly estimated as clay. Then follows 10 



