SURVEY OF COLORADO AND NEW MEXICO. 75 



dike. In nearly all cases tlie strike of the axes of these dikes is nearly 

 northeast and southwest, while for the most part the axes of the granitic 

 ranges trend about northwest and southeast. It is my opinion also 

 that the elevation of the basaltic range was an event subsequent to 

 that of the granitic, for in all cases that I have ever examined the igne- 

 ous rocks are poured out over the granites, and in some cases conceal- 

 ing them entirely over large areas. Many of the loftiest peaks in the 

 granitic ranges are basaltic. The basaltic axis nev^er passes through 

 the granitic, as is shown by the Spanish peaks on the east, and the 

 Sierra Blanca on the west. Each one stoics abruptly as it comes up 

 against the principal granitic axis. 



As I have before observed, no unchanged sedimentary rocks of older 

 date than the Santa Fe marls were noticed along the western side of 

 the main range north of Taos, until we come to the Sangre de Christo 

 Pass. About the sources of the Costilla or Culebra Kivers there may be 

 some remnants, but none have been seen after a pretty close examina- 

 tion. At the very summit of the pass is a series of reddish sandstones 

 and shales nearly vertical but inclining westward. From the summit of 

 the pass we descend the beautiful valley of the Sangre de Christo 

 Creek in a southwesterly direction. The sandstone extends for four or live 

 miles, and is of every variety of texture, from a very fine comj^act sili- 

 cious rock to a moderately coarse iDudding-stone. In some of these 

 sandstones are indistinct vegetable impressions, some of which can be 

 recognized as fragments of Calamites Further down we come to a series 

 of limestones and sandstones, with some calcareous sandstones, having 

 thin beds or partings of shale. These alternate limestones and sand- 

 stones extend for about five miles, and then comes a belt of five miles 

 of gneissoid granites. Near the junction of the limestones with the 

 granites there is a bed of limestone filled with fossils, Productus^ several 

 species, Spirifer suhtilita, Rhjjnconella rocTcymontana, Spirifer lineatus, and 

 numerous corals and crinoidal stems. Although it is possible that there 

 are here rocks of older date than carboniferous, yet from the fact that 

 all along the eastern side of the mountains the carboniferous limestones 

 have been found resting upon the granites, I have inferred that there 

 are no sedimentary rocks of older date in this region. At first the Sangre 

 de Christo Creek passes through a monoclinal rift for nearly ten miles, 

 then it cuts through ridges of limestone, bed after bed. The real dip of 

 all these beds is northeast while the apparent dij) is southwest, as if 

 the granites were more modern than the limestones which are above them. 

 The belt of granites is about five miles wide, and thence to Fort Garland, 

 which is ten miles, are igneous rocks. Eight miles east of Fort Garland 

 are some high ridges of basalt that dip east about eight degrees, and 

 have a trend north and south, and from the abrupt western face from 

 four to six distinct beds of igneous rocks can be seen. The cause of 

 the inclination of the basaltic beds is not clear, though it may have 

 originated in the Sierra Blanca. We were much indebted for many 

 favors and information to Dr. E. McClelland, surgeon, and to Colonel 

 Hart, commander of Fort Garland. 



CHAPTEE IX. 



FROM FORT GARLAND TO SOUTH PARK. 



The Eio Grande del Norte Eiver rises in the Park of the Animas, flows 

 east about one hundred and fifty miles to the San Luis Yalley, then bends 

 abruptly south through the middle of the San Luis Yalley. The north- 



