424 A. W. GRABAU THE SHERBURNE SANDSTONE 



Prosser^ has given a fuller and more detailed description of this rock in 

 the various sections from the Chenango Eiver eastward, and these serve 

 as a basis for our understanding of the relationship of this to the inclos- 

 ing formations. More recently still, Dr. John M. Clarke has discussed 

 certain characters of these sandstones, and to this reference will be made 

 farther on in this paper.* 



The TYPICAL Sherburne Sandstone 



GENERAL DESCRIPTION 



The rock of the type region is a bluish, rather fine-grained sandstone, 

 frequently of the tj^pical bluestone character, alternating with smooth 

 shales. Near Smyrna these rocks are mostly bluish, unfossiliferous, and 

 arenaceous shales, with thin and thick bedded sandstones with irregular 

 markings on their upper surfaces, mainly of a mechanical nature. Some 

 of the sandstone layers are quarried, these ranging in thickness up to 

 19 inches. West of Smyrna a few fossils of the Naples type, including 

 Pterochaenia fragile (Hall), still occur,^ while in the lower part there is 

 a direct lateral passage of this Sherburne shale and sandstone into the 

 impure Tully limestone and the sparingly represented Genesee shales. 

 Prosser^ ascribes the eastward disappearance of the Tully limestone ^^to a 

 gradual loss of the calcareous material, which is replaced by that of the 

 arenaceous and arigillaceous sediments, causing the rock to present a de- 

 cidedly different lithologic appearance.'^ 



The total thickness of the Sherburne in the Chenango Eiver section 

 is about 250 feet and shales seem to predominate. While in a few sec- 

 tions near Smyrna a little of the Tully and Genesee are still represented, 

 these are for the most part absent, the Sherburne resting directly wpon 

 the fossiliferous Hamilton shales and sandstones. The Sherburne itself 

 is devoid of marine fossils, except that in this region a few intercalations 

 of dark shales occur, usually in its lower part, Avhicli carry a remnant of 

 the Naples fauna, so much more abundantly developed in the equivalent 

 rocks farther west. Thus, in the gorge of Nigger Brook, 1% miles 

 south of Sherburne village, Prosser found blackish shales at a horizon 



3 C. S. Prosser : The classification and distribution of the Hamilton and Chemung 

 series of central and eastern New York. 16th Ann. Rept. New York State Geologist, 

 pt i, pp. 87-222. Prosser calls attention to the fact that the "Sherburne" flagstone of 

 Vanuxem's 1840 report are different from the beds comprised in the "Sherburne" group 

 of Conrad's 1841 report, these latter belonging in the Hamilton group below the Tully 

 limestone. 



■» John M. Clarke : Strand and undertow markings of Upper Devonian time as indica- 

 tions of the prevailing climate. New York State Museum Bulletin 196, April, 1917, 

 plates 7-25, pp. 199-210. 



" Prosser : Loc. cit., p. 119. 



« Loc. cit., p. 118. 



