1182 NEW YORK STATE MUSEUM 



middle cement series, comprising the Rondout, Cobleskill and 

 Salina waterlimestone; and the lowermost Wilbur limestone. 

 These formations are exposed along the steep eastern slopes of 

 the Ylightberg and North hill where they are found dipping at 

 high angles into the hills to the northwest ; and some portions of 

 the series, specially the Manlius limestones, are exposed above 

 the overthrust on the North hill, and also below the Ylightberg 

 overthrust plane along the road running to the top of the Vlight- 

 berg at the point marked K on the map. 



Wilbur limestone 

 This lowest member of the upper Ontaric limestone series lies 

 unconformably on the eroded edges of the tilted Champlainic 

 sandstones. It is a dark colored argillaceous limestone 5 to 7 

 feet thick, which on weathering turns brown. In places it is 

 highly fossiliferous, containing corals, crinoid fragments, brachi- 

 opods, mollusks and some trilobites. The fauna of this lime- 

 stone, which has long been known as the " coralline " and which 

 has recently been termed Wilbur limestone, is described in Mr 

 Hartnagel's paper in another part of this volume, and details 

 of the unconformity at the base of the Wilbur beds are 

 described below [p. 1209]. 



Cement series, comprising the Salina, Cobleskill and Rondout 



beds 



These cement beds have been variously called Salina, Water- 

 lime, Manlius, Onondaga etc., and till recently [see HartnagePs 

 paper on Preliminary Observations on the Cobleskill ("Coral- 

 line") Limestone of New York, p. 1109] no attempt has been 

 made to definitely correlate them with any portion of the Siluric 

 section of western and central New York. They consist of nine 

 distinctly marked layers of limestone aggregating about 32 feet 

 in thickness. 



The following detailed section of the strata exposed in the 

 Spring and Delaware avenue quarries where the softer beds have 

 suffered the least amount of crushing, and which shows the 

 relations of the cement beds to each other and to the under and 

 overlying formations, may be taken as typical of the Ylight- 

 berg vicinity. The names given to the cement beds are those 

 applied by the miners. 



