2 INVESTIGATION OF OTEEO BASIN FOR POTASH SALTS. 



will throw light upon the probabilities of the deposition of salines 

 during earlier geologic time, their existence beneath the present 

 surface, and the presence of potash salts among them. In particular, 

 search must be made for any direct evidence along this line, such 

 as the records of deep wells, the composition of spring and well 

 waters from the buried beds, etc. 



All these inquiries look toward the discovery of the actual location 

 of possible deposits of potash. There are, however, certain additional 

 criteria as to the probable presence or absence of potash somewhere 

 within the basin, the exact location remaining unindicated. These 

 have to do with the matter of source. It is well known that potash 

 salts, wherever found, are derived from the decay of potash-bearing 

 rock minerals under the action of weathering and the surface waters. 

 If, then, the rocks composing the drainage area of any undrained 

 basin contain large amounts of such minerals, and if the waters now 

 flowing over these rocks and into the basin are hirh in potash, 

 potash deposits may be suspected. A scarcity of potash in rocks or 

 waters strongly implies its absence from the basin. 



In summary, the examination of a suspected area should include: 



(1) A study of the central sink or sinks. Are there any potash 

 beds on the present surface? 



(2) A study of the geologic history. Are any buried saline beds 

 probable ? 



(3) A chemical study of waters from any deep wells, deep-se;;ted 

 springs, etc., on the basin floor. Do the buried salines, if any, con- 

 tain potash ? 



(4) A study of the composition of the rocks of the drainage area. 

 Is there any visible source of potash ? 



(5) A chemical study of the present drainage waters. Js potash 

 now entering the basin ? 



In the reconnoissance of the Otero Basin all of these questions 

 were kept constantly in mind, and an effort was made to answer all 

 of them as fully and finally as possible. The conclusions fo'iow. 

 The topographic and geologic characters of the region, which wi ! l he 

 fully described elsewhere, need not be reviewed. 



The sink of the basin is the old lake bed or playa west of the White 

 Sands. It has not been minutely explored, but enough is known of 

 it to warrant the assertion that its surface is everywhere composed 

 of loose gypsum. This gypsum is usually more or less saline, and 

 in one place (Lake Lucero) a bed of mirabilite, or crystallized hydrous 

 sodium sulphate, lies just under the surface. No other deposits of 

 segregated salts are known. A complete chemical analysis was made 

 of the water-soluble portion of the loose gypsum overlaying the mini- 

 bilite bed, and the results are given in Table I. 



