TO JUNCTION OP GRAND AND GEEEN EIVERS. 107 



taceous series, quite rich in fossils. Perhaps a hundred feet above the sandstones is a 

 band of brown, shelly, sandy limestone, which forms a projecting ledge in the face of 

 the cliffs, giving cornices and capitals to the castles and palaces into which they have 

 been worn. This ferruginous stratum marks a distinct horizon, and may be traced 

 over an immense area in New Mexico. It is the same that I have before referred to in 

 my notes on the banks of the Dolores, Camp 21, the Pagosa, the ford of the Chama, 

 Galisteo, and the banks of the Canadian. This stratum is characterized by the following 

 fossils: Inoceramus problematicus, Ostrca luyubris, Scaphites larvlformis, Ptychodus Whip- 

 plci, &c. Several undescribed species of Inoceramus, Ostrea, Ammonites, &c., are also 

 found in it; one of the Inocerami, abundant at Camp 39, being 2-3 feet in diameter. 

 The place of Gryphaa Pitcheri is just beneath this stratum; while the overlying shales 

 are filled with fragments of a large Inoceramus, covered with the closely-set shells of 

 Ostrea congcsta. 



"A few miles north of Camp 39 is the southwestern corner of the Mesa Verde, which 

 stretches from this point northward to our former trail, and, eastward, forms the north 

 bank of the San Juan as far as the eye can reach. It has an altitude of 2,000 feet 

 above camp, and presents, with its many detached buttes and pinnacles, its long and 

 lofty walls, a most grand and imposing object. On the south side of the river, now 

 quite near to us, stand out in strong relief the picturesque basaltic pinnacles of ' The 

 Needles,' while further south the view is bounded by the high ridges of the Carisso and 

 Tunecha Mountains." 



From Camp 40 we obtained a nearer and still better view of "The Needles," which 

 is represented in the accompanying lithograph plate. 



This is a mass of erupted rock, rising with perpendicular sides from the middle of 

 the valley. From all points, where seen by us, it has the appearance of an immense 

 cathedral, of rich umber-brown color, terminating in two spires. Its altitude is about 

 1,700 feet above its base; above the river 2,262 feet. It is everywhere surrounded by 

 stratified rocks, and its isolated position and peculiar form render its origin a matter of 

 some little doubt. My conviction, however, is very decided that its remarkable relief 

 is due to the washing away of the sediments which once surrounded it, and which 

 formed the mold in which it was cast. In no other way can I imagine its vertical 

 faces of 1,000 feet to have been formed. 



For ten miles after leaving Camp 40 we were traveling along the trough of the 

 river excavated in the Middle Cretaceous shales; the Upper Cretaceous sandstones cap- 

 ping the bluffs on either side. We here reached what seemed to be, in the distance, a 

 mesa wall crossing the river. This proved, however, to be a mass of dislocated and 

 ruptured strata, forming a huge broken wall, similar to that described in the Geology 

 of the Colorado Expedition, page 95, called by the Mexicans the Creston. This wall 

 marks a great line of fracture which traverses the country in a zigzag course from the 

 Sierra de la Plata southward toward the Tunecha Mountains. It crosses the river 

 nearly at right angles, with a trend N. 20 W. magnetic, forming a wall several hun- 

 dred feet high, cut by the river in a narrow passage, through which we worked ourway 

 with extreme difficulty. 



The Creston evidently once formed a dam across the valley of the San Juan, over 



