468 PRINCIPLES OF STRATIGRAPHY 



Rothpletz (36) has noted that the genera Gloeocapsa and Glceo- 

 thece, which are rich Hme-secreters, form snow-white ooUte grains 

 which are scattered among the sand and pebbles of the low shores, 

 and blown landward into dunes ranging up to 6 feet in height. 

 "The cells of the Gloeocapsa are 2 ^ * in diameter and spherical, 

 those of the Gloeothece 2 to 3 /a thick and 4 to 5 /a long. The lime 

 is enclosed in the alga-body in the form of rounded tubercles, which 

 often mass themselves together into larger irregular tubercular 

 bodies. It is a fine-grained aggregate of calcite which always en- 

 closes numerous dead alga cells that have already lost their green- 

 ish coloring." Three forms were recognized: ist, irregular tuber- 

 cular bodies, several millimeters in diameter ; 2nd, spherical or oval 

 forms, about one-third millimeter in diameter ; and, 3rd, thin rods, 

 about half a millimeter long and one-tenth millimeter broad. These 

 oolites are forming day by day through the secretion of lime by 

 these algae. 



Since analysis of the water of Great Salt Lake (see Chapter 

 IV) shows only a small quantity of calcium chloride or sulphate 

 and no carbonate, no lime would be precipitated from the lake it- 

 self, except for the activities of these minute plants. When it is 

 considered, however, that the streams tributary to this lake bring 

 in quantities of carbonate of lime, all of which is precipitated as 

 oolite grains, it becomes a question whether the algous growth is 

 so active as to use up all this lime or whether "the strong brine of 

 the lake seems to be incapable of holding calcium carbonate in solu- 

 tion" (Clarke-8:/^(5) and it is therefore precipitated chemically.f 



Similar oolites are forming on the shores of the Red Sea, where 

 they are widely distributed along the west coast of the Sinai penin- 

 sula. Here they are drifted inland often for many kilometers, or 

 even days' marches distant from the shore, and constitute white 

 dune sands of oolitic material, a continental formation built of 

 material of marine origin. These grains generally contain vermi- 

 form and often branching canals, more or less filled with calcite. 



* I H = o.ooi mm., called a micron. 



t Of the rivers tributary to Great Salt Lake, the following may be noted 

 with their percentage of CO3 and Ca (Clcivke-S -J 45): 



CO3 Ca 



A. Bear River at Evanston, Wyoming 52 . 68 23 . 69 



B. Bear River at Corrine, Utah 21 .53 10. 12 



C. Jordan River at intake of Utah and Salt Lake 



Canal 2 . 67 7 . 59 



D. Jordan River near Salt Lake City trace 10.26 



E. City Creek, Utah 52-57 24. 19 



F. Ogden River at Ogden, Utah 33-68 16.05 



G. Weber River at mouth of Canyon 40.00 18 . 19 



