TO JUNCTION OF GRAND AND GREEN RIV.ERS. 05 



CIIA.P'TER IV. 



GEOLOGY OF THE ROUTE FROM SANTA FE TO THE SIERRA LA 



PLATA. 



STRUCTURE OF THE VALLEY OF THE Rio GRANDE THE VALLEY OF THE CHAMA ABIQUIU- 

 (JorrER MINES FOSSIL PLANTS RUINS OF Los CANONES ABIQUIU PEAK PLATEAU 

 COUNTRY BORDERING THE UPPER ClIAMA ARROYO SECO TRIASSIC MARLS NAVA.TO 

 SPRING CRETACEOUS SANDSTONES AND PLATEAU BANKS OF THE NUTRIA MIDDLE CRE- 

 TACEOUS BEDS V ADA DEL CHAMA SECTION OF VALLEY OF THE ClIAMA HIGH MESA 



OF UPPER CRETACEOUS ROCKS LAGUNA DE LOS CAVALLOS DIVIDE BETWEEN THE 

 WATERS OF THE RlO GRANDE AND SAN JUAN GENERAL VIEW OF THE STRUCTURE OF 

 THE SURROUNDING COUNTRY MOUNTAIN CHAINS BELT OF FOOT-HILLS TABLE LANDS 

 Rio NAVAJO CERRO DEL NAVAJO SIERRA DEL NAVAJO RITO BLANCO THE PAGOSA 

 SIERRA SAN JUAN AND ASSOCIATED MOUNTAIN RANGES CRETACEOUS ROCKS AND FOS- 

 SILSTHE PIEDRA PARADA Rio PIEDRA BROKEN MESA VIEW FROM HIGH DIVIDE- 

 RIO DE LOS PINOS SIERRA DE LOS PINOS Rio FLORIDO VALLEY OF THE ANIMAS 

 RUINS ON THE ANIMAS CROSSING OF THE ANIMAS STRUCTURE OF THE MOUNTAINS 

 DRAINED BY THE ANIMAS RlO DE LA PLATA DELIGHTFUL CAMP CRETACEOUS ROCKS 

 AND FOSSILS SIERRA DE LA PLATA METALLIFEROUS VEINS OF THE SIERRA DE LA PLATA. 



VALLEY OF TOE RIO GRANDE. 



The structure of the Rio Grande Valley seems to be essentially the same 

 throughout, its entire extent that is, as far as it is really a valley, viz., from its 

 northern extremity to El Paso. Throughout all this interval it is a synclinal 

 trough, lying between imperfectly parallel ranges of mountains. At El Paso the 

 river breaks through its eastern wall, and, thence to its mouth, follows a devious 

 course determined by the local obstacles which it meets, no longer modified by the 

 meridional topography of the Rocky Mountain system. Opposite and above Santa Fe 

 the trough in which the river flows is bounded on the east by the lofty ranges of the 

 Santa Fe Mountains and their northern representatives, which extend in an unbroken 

 series to the Parks ; on the west, immediately opposite Santa Fe, by the bold and 

 picturesque chains of the Valles. These mountains have but a limited extent, falling 

 oflf suddenly on the north, and leaving a low pass, which is traversed by the Chama. 

 Xorlh of the Chama they are succeeded by the mountains of Conejos, which connect 

 with the wide-spread and tangled maze of high sierras, to which I have referred in the 



9SF 



