221 



before our visit made some hasty examinations of this portion of Crow- 

 ley's Ridge. On pages 28-29 of his report on his work in this section he 

 called attention to* a low "range of quartzose sandstone" which had 

 "all the lithological characters of the Potsdam * * •■, as it occurs on the 

 Minnesota and Wisconsin rivers in the northwest." Two localities had 

 been noticed by him both of which were in Craighead county. The refer- 

 ence of these rocks to the Potsdam or to any part of the paleozoic made 

 the locality one of great interest, occurring, as it does, in the heart of a 

 region of pleistocene soils underlain by rocks known to be of tertiary age. 

 There was a peculiar (satisfaction when Mr. William Lane piloted me to 

 the very spot where, forty years before, he had piloted Dr. Owens and 

 placed me on the pinnacle of the very rock from which that eminent geol- 

 ogist had looked over the heavily forested valley of the Cache. It is not 

 surprising that these rocks were with some hesitation referred by Owen to 

 the Potsdam. They present every characteristic of the Potsdam of north- 

 ern New- York except that they are entirely devoid of fossils, or at least 

 this locality yielded none. His reference was plainly made from lithol- 

 ogic characters and though wrongly made was excusable for his time. 

 This particular locality is at the foot of a high spur of the ridge forty feet 

 or more above the Cache bottoms. The hills are high and are crowned 

 with heavy beds of gravel which, in turn, are overlain by a thin sandy 

 and gravelly soil supporting a strong growth of the common short leaved 

 pine {Pinus mitig) and much scrub oak. At this point the quartzose bed is 

 a huge mass of very hard rock, ringing like clinkstone when struck with 

 the hammer, having its sand grains and the few accompanying pebbles 

 well waterworn and exhibiting the characteristic structural features of 

 sandstones deposited in swiftly running waters or tide swept shallows. 

 The dip that appeared so patent to Owen developed into simply planes 

 made by false bedding. A few hundred feet north of the roadway across 

 which this mass of rock extends, in a deep ravine in which the rock is ex- 

 posed to excellent advantage, the sandstone outcrops as a series of ledges 

 from near the level of the bottoms to a point two-thirds of the way up the 

 hill, thus showing a thickness of fully ninety feet. The several starta are 

 from five inches to five oi more feet in thickness and are nearly or quite 

 horizontal. The total exposure of the rocks in this locality is about half 

 a mile in length. At this point the underlying strata could not be seen 



-First tinuual report of a geological reconnoissance of the northern counties of Ar- 

 kansas. Pp. 28-29. 



