32 DESCRIPTIVE GEOLOGY. 



Lime - 34.95 



Magnesia " 17.36 



Carbonic acid 46.55 



Insoluble residue 0.34 



Alumina and ferric oxide 0.16 



Water 0.23 



100.11 



The uppermost stratum of limestone and the bed immediately under- 

 lying the Triassic Red Beds at Horse Creek is an exceedingly fine-grained 

 homogeneous rock, of a deep flesh-red color. Scattered through it are small 

 white cr3^stals of calcite. This rock, as in a measure typical of the upper 

 light-colored limestones, was also subjected to chemical analysis, and found 

 to be a nearly pure dolomite, the impurity being a little silica. 



It yielded as follows : 



Carbonate of lime 60.09 



Carbonate of magnesia 39.20 



99.29 



The characteristic layer of red arenaceous limestone, near the base of 

 the limestone series, is usually a well-defined bed. A specimen in our 

 collection from near Granite Canon presents a compact texture and a 

 smooth even fracture. To the eye the rock shows a slightly-banded 

 structure, which is somewhat more marked in the thin microscopic sections. 

 Under the microscope, the rock reveals the presence of small crystals of 

 calcite and numerous angular grains of sand. 



As already mentioned, the only fossils found in these beds are such as 

 are characteristic of the Coal-Measure formations. Numerous fragments of 

 crinoid stems and highly-altered impressions of molluscan forms, too poor 

 for determination, are found throughout the limestones in many localities; 

 but well-preserved specimens are somewhat rare, or at least were not col 

 lected by our parties. They are all comprised, within the Brachiopoda; 

 the following being identified : 



j» 



