Maryland Geological Survey 177 



Helderberg Formation 



Vertical Total 



Becraft Member tiiickuess vertical 



teet thickness 



Light gray limestone free of chert. Spirifer concinnus (aa), 

 8. cyclopterus (a), Meristella arcuata (c), Anoplotheca concava 

 (rr), Rensselaria subglobosa (aa), Plethorhyncha campbellana 

 (aa), Eatonia medialis, E. sinyularis (r), E. peculiaris (rr), 

 Leptwna rhomboidalis (rr), Schuchertella woolworthana (aa), 

 Strophonella punctulifera (r), Rhipidomella oblata ? (r) 25.0 162.0 



Light gray limestone with numerous bands of black chert 20.0 137.0 



Almost pure light gray limestone with a few nodules and 

 one or two layers of chert. Spirifer concinnus (aa), Rensse- 

 la'ria subglobosa (c), Plethorhyncha campbellana (r), Eatonia 

 medialis (r), Schuchertella woolworthana (r) 25.0 117.0 



Mostly black chert in irregular nodular layers, some limestone 

 near the top 17.0 92.0 



Talus slope. Fossils from the higher zones: Spirifer con- 

 cinnus (aa), /S. perlamellosus (rr), Anoplotheca concava (rr), 

 Meristella arcuata (a), RensseUrria subglobosus (c), Eatonia 

 peculiaris (r), E. medialis (r), Plethorhyncha campbellana 

 (rr), Strophonella punctulifera (rr), Stropheodonta planulata 

 (r), Leptwna rhomboidalis (c), Schuchertella woolworthana 

 (c), Rhipidomella oblata (r), Tentaculites elongatus (rr) 40.0 75.0 



Thickness of Becraft member 127.0 



T<leio Scotland Member 

 Light gray limestone with very numerous layers of light 

 colored almost white chert at the bottom. Blacker near the 

 top. Spirifer macropleurus (a), Meristella arcuata (c), Stro- 

 phonella punctulifera (r), Leptwna rhomboidalis (a) 25.0 35.0 



Thickness of New Scotland member 25.0 



Coeymans Member 

 Light gray almost quartzitic sandstone, crinoid stems 10.0 10.0 



Thickness of Coeymans member 10.0 



The Becraft member is well developed and sharply defined both litho- 

 logically and paleontologically. It is at least 87 feet thick and it may 

 possibly be over 100 feet, and much thicker than it is in the typical New 

 York section and nearer to that of the Port Jervis, New York, section.* 



The New Scotland member is about 25 feet thick and contains much 

 white chert. The Coeymans member is an almost white qaurtzitic sand- 

 stone, a feature not known in the Helderberg of Maryland west of this 

 point. This pure sandstone is probably caused by the carrying away by 



* Barrett, S. T. Ann. N. Y. Lyceum Nat. Hist., vol. xi, 1876, pp. 290-299. 

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