44 COLORADO COLLEGE STUDIES. 



the Canadian river and southward, but their extension there 

 has not been seen by the writer, unless certain Hmited ex- 

 posures seen low down in the valley of that stream beneath 

 a mantling of Neocene near Canadian, Texas, are part of 

 them. 



THE DAY CREEK DOLOMITE. 



Upon the latest of the Red Bluff beds rests a persist- 

 ent stratum of dolomite, varying from less than a foot to 

 five feet or more in thickness. This is the same as the 

 "gray, cherty, sometimes gypsiferous limestone" noticed 

 by Professor St. John* as occuring in Clark county at the 

 head of Day creek. It is a true dolomite, containing with 

 the carbonate of lime an equal or even greater percentage 

 of carbonate of magnesia, as indicated by a qualitative an- 

 alysis kindly made for the writer by Prof. William Strieby 

 of Colorado College. Though not of great thickness, it is 

 an important member of the upper Permian of southern 

 Kansas and northern Oklahoma owing to its persistence, 

 which makes it a convenient horizon of reference. It may 

 therefore be considered a formation by itself and, to dis- 

 tinguish it from other and less important dolomites of the 

 Cimarron series, be called the Day Creek dolomite, after 

 the above-named locality of its occurrence. 



The stone is nearly white in fresh fracture, weathers 

 gray, and often has a streaked and gnarly grain crudely 

 resembling that of fossil wood. It is more or less cellular 

 and, in places, cancellated. Irregular nodules of limonite 

 are here and there imbedded in it. Its cherty hardness and 

 fracture are not due to the presence of silica, as one is 

 tempted to infer, but are characters belonging to it as a 

 dolomite. It is a durable building-stone, as shown by the 

 old buildings and corral-walls of the Fares ranch on West 

 Bear creek, which are built of it; but it is somewhat diffi- 

 cult to trim to desired shapes owing to its erratic fracture, 



*Note8 on the Geology of Southwestern Kansas, 1. c, page 141. 



