Prosser—Straligraphie Position of Hillsboro Sandstone. 435 



Art. XXXI. — The Stratigraphic Position of the Hillsboro 



Sandstone* ; by Charles S. Prosser. 



Historical Review^ 

 Sections on Quaker Hill. 

 Sections near Hillsboro. 

 Sections near Turkey. 



HISTORICAL REVIEW. 



The Hillsboro sandstone was named and described by Dr. 

 Orton in 1871,+ who stated that "As a typical example of it 

 occurs so near Hillsboro [top of Lilley's HillJ, it may be appro- 

 priately designated the Hillsboro sandstone.'";}: Dr. Orton 

 called this sandstone the upper and "6th member of the 

 Niagara series in southwestern Ohio," and described the out- 

 crops on Lilley's Hill as "a very fine-grained, purely silicious 

 sandstone, about 30 feet thick, [which] directly overlies the 

 Pentamerus beds at this point. The color of the rock varies 

 from white to yellowish or brown, a small but varying propor- 

 tion of iron seeming to account for the changes. There is a 

 peculiar glistening appearance to the sandstone which makes it 

 impossible to confound it with any other formation found in 

 this part of the State."§ 



" The Geology of Highland County," by Dr. Orton, contains 

 the following account of this sandstone : 



"At Hillsboro, and on the eastern border of the county gener- 

 ally, a silicious sandstone of a good degree of purity is found 

 terminating the [Niagara] series. Its composition is shown in 

 the following analyses by Dr. Wormley : 



Silica 94-10 



Iron and alumina 3 "60 



Lime-carbonate 1 "30 



Magnesia-carbonate 0*39 



The thickness of this sandstone in Lilley's Hill is 30 feet, and 

 no greater thickness has been elsewhere observed. The sand that 

 makes up the rock is fine-grained and but slightly cemented, 

 crumbling easily from exposure to the weather or from mechani- 

 cal abrasion. In color, it varies from white to deep yellow. 

 There is always a glistening appearance about it which is a dis- 

 tinguishing characteristic of the rock. No fossils but a poorly 



* Published by permission of the State Geologist of Ohio. Read before 

 Section E of the American Association for the Advancement of Science at 

 Columbus, Ohio, on December 28. 1915. 



f Geological Survey of Ohio. Report of Progress in 1870, pp. 271, 283- 

 285, 301, 306. 307, 309, and figs. 1, 3, 4, 5 and 6. 



{Idem, p. 306 § Idem, p. 306. 



