1877.] OoO [Ashburner. 



No. VI. Lewisiown [Pre-meridian— Lower Helderhenj,) Limestone. 



Thickness : (Nos. 43 to 38 inclusive) 162 feet. 



Cliaracter : Consists of massive, dark blue and gray, semi-crystalline 

 limestone, containing toward the upper and lower parts alternating layers 

 of gray shaly limestone and argillaceous lime shale. To the north-east in 

 the Juniata Valley from Mount Union to Lewistown, the shale at the top 

 of the mass becomes a thicker and more distinctive formation. There are 

 fine exposures of the series along the Kisicoquillas creek, near Lewistown, 

 Mifflin County, where it was found necessary to give it a new geographical 

 name in the failure to identify it Avith any of the sub-divisions of the lower 

 Helderberg group in New York. 



The following fossils have been determined : Acervularia, Alveo- 

 lites minima, Astylospongia inornata, Merista Icevis, Orthis ohlata, Pen- 

 tamerus gaJeatus, Rhynchonella formosa, Astylospongia, Atrypa reticu- 

 laris, Aulopora, Uonopliyllum, Merista arcuata, 8tromatopora, Trematos- 

 pira formosa, and Zaphrentis. 



This formation with the Oriskany is ridge making, and of great eco- 

 nomical importance, as it furnishes good lime for building and agricultural 

 purposes, besides being an excellent flux in the iron fui-nace. A speci- 

 men from Saltillo contained : Carbonate of lime 90.904 ; carbonate of mag- 

 nesia 3.162. 



An iron ore having a laminated structure occurs sometimes scattered in 

 the soil overlying the limestone. 



Water-hm« (Scalent) Cement Beds. 



Thickness : (Nos. 37 to 28 inclusive) 580 feet. 



Character : Consists for the most part of a blue and gray flaggy and 

 thinly bedded limestone having a wavy stratification. Toward the top the 

 limestone is massive, slightly argillaceous and of a dark gray and bluish- 

 gray color ; but toward the bottom it becomes flaggy, thinly laminated 

 and shaly, having a brownish-gray and yellow color. In the lower part 

 limestone alternates with green, yellow and gray argillaceous shale. 



The strata in the central part contain a great deal of calcite, and the sur- 

 faces of the stone are oftentimes coated with carbonaceous matter, and 

 show ' • slickensides. ' ' The limestone beds are frequently highly magnesiau, 

 and a few may be compared economically with the Lewistown limestone. 

 The outcrops occupy a small valley at the foot of the Oriskany ridge 



Onondaga (Scalent) Marls. 



Saltillo and Three Springs. Orbisonia. 



Thickness : Upper member Nos. 27, 26 and 25 170 db feet. 145 feet. 



Lower " " 24,23 " 22 270 ± " 230 " 



The upper member consists of yellow, gray and greenish shaly and argil- 

 laceous (fossiliferous) limestone in thin beds, alternating with olive, green 

 and gray calcareous shale. 



The lower member consists of green, yellow and gray calcareous shaie, 



