TOPOGKAPHIC FEATUKES OF THE DESEET BASINS. 49 



elusions of some geologic interest but quite foreign to the present subject. The area 

 of the Otero Basin is a little over 7,000 square miles. 



THE ESTANCIA BASIN. ^ 



The Estancia Valley lies at the northern end of the trough in which is the Otero Basin 

 and where this trough begins to merge with the plateau of northern New Mexico. It is 

 separated from the Otero Basin by the Gallinas and Chupedera uplift and the northern 

 and western boundaries are similarly structural. The eastern boundary is much lower 

 and in several places is less than 250 feet above the bottom of the valley. Overflow in 

 this direction and into the Pecos Valley is possible but not probable. The bottom of 

 the valley is diversified by a number of shallow and irregularly-shaped depressions, 

 believed by Meinzer to have been scooped by the wind from the beds deposited in the 

 bottom of an ancient lake. Some of these depressions now contain salt or brackish 

 lakes. There is the usual series of old strands about the valley. 



At present the drainage of the valley is almost entirely by underflow and impos- 

 sible to define. The area is about 2,050 square miles. In the northeastern corner is 

 the small basin of White Lake, now cut off by desiccation but once a tributary. 

 Including this the area is about 2,100 square miles. Both of the areas given are 

 only approximate because of the comparatively low relief of the surrounding highlands 

 and the difliculty of accurately defining the divides. 



THE ENCINO BASIN. 



The Encino Basin lies east of the Estancia Basin and is very similar to it. The 

 surrounding divides, though poorly defined, are relatively high and the basin has 

 probably been permanently inclosed. It contains the usual saline depression, 

 believed by Meinzer to be wind-formed, and is surrounded by the usual series of old 

 strands. Its area is about 300 square miles, great accuracy being unobtainable 

 because of uncertainty as to the position of the divides. 



THE FINOS WELLS BASIN. 



The Pinos Wells Basin lies just south of the Encino Basin and is similar thereto in 

 every way except that the eastern divide is much lower and the lake strands are 

 lacking. The writer is of the opinion that this basin was once tributary to the Pecos 

 Valley and has only recently been inclosed. It is not impossible that this basin is a 

 part of a former eastward overflow channel of the Estancia Basin and, if the Estancia 

 Basin ever did overflow, it was probably by this path. The area of the Pinos Wells 

 Basin is about 325 square miles. 



THE SALT BASIN. 



Directly southeast of the Otero trough, though probably not structurally related 

 thereto is another similar trough which contains the so-called Salt Basin, historic 

 as the scene of the "salt riots" of 1878. The divides which suiTound this basin are 

 essentially structural and ancient and though several passes are superficially alluvial, 

 all are over 600 feel above the flat. The basin is believed to have been permanently 

 inclosed. The floor is a nearly level plain dotted with hillocks of dune sand and with 

 small saline lakes and playas. The present drainage is insigniflcant and the areas 

 tributary to the various lakes can not be computed with any exactness. The area of 

 the basin as a whole is about 8,600 square miles. 



1 The description of the Estancia, Encino, and Piaos Wells Basins is drawn largely from the report of 

 Meinzer, U. S. Geol. Surv.; Water Supply Paper 275 (1911). 



