REPORT ON FIELD WORK IN GEOLOGY. I 23 



particularly noticeable in the bluffs at one point west of Lawrence, 

 although in most places in that vicinity the lower and thickest layers 

 do not reach more than twenty inches. 



The rock when perfectly fresh and iinweathered is a light blue, but 

 in almost all instances where quarries have been opened it is changed 

 to a light buff color. On account of the compact, fine even texture 

 the rock is unusually valuable for structural purposes, being surpassed 

 by but few limestones in the state. The main building, and the 

 chemical building, as well as the new library building at the Univer- 

 sity are constructed of it, and also many handsome and durable 

 edifices in the city. 



The rock is exceedingly fossiliferous, much more so than any other 

 one met with in this section. It contains crinoids, brachiopods, and 

 other invertebrates unevenly distributed through it to such an extent 

 that in certain localities they are quite remarkable. In other places 

 fossils seem to be quite scarce, so that there is a great diversity of 

 conditions in different localities. In allusion to Mt. Oread, the hill 

 upon which the university stands, and where this limestone is so well 

 exposed, it will be called the Oread limestone. 



The north and south extent of the Oread limestone is yet undeter- 

 mined. To the north it reaches far beyond the limits of this section, 

 producing the hills or bluffs on the north bank of the Kaw river so 

 similar to those on the south. To the southwest it probably reaches 

 the Neosho river, although exact correlations have not yet been made. 

 By the close of another season it is hoped such questions may be 

 definitely determined. The southeastern limit of this system is also 

 known for a short distance only. Blue Mound, near Lawrence, and 

 the hills on the environs of Baldwin City seem to be the limit in that 

 latitude, but it has not been traced farther south. Most probably the 

 high hills to the west of Princeton are capped with it. 



The peculiar character of the effects of erosion on a terrain com- 

 posed of alternating hard and soft strata is well represented in the 

 environs of Lawrence, and the resulting topography is intensified on 

 account of the unusual thickness of the readily yielding shale between 

 the Ottawa and Oread limestones. The protection of the hard limestone 

 results in the formation of table lands and plateaus with broad valleys 

 intervening, the depth of which is determined by the vertical thick- 

 ness of the softer shales. Occasionally a portion of the limestone area 

 becomes detached from the main body by erosion, breaking through 

 between it and the main land and in this way separate hills or mounds 

 are formed. The Blue Mound, seven miless southeast of Lawrence, 

 is a good illustration of this.* 



*This subject is better discussed in the paper on Topographic Features of Eastern 

 Kansas which appears in this number of the Quarterly. 



