The problem presented by the nearly barren early Silurian formations of southeastern New York is of long standing. The basal deposits were named the Shawangunk by Mather in 1840.3 They were long considered to be Medinan in age because of their lithology and their position beneath supposed Niagaran limestone.
Hartnagel subsequently showed that the limestone is not Niagaran but late Silurian Cobleskill,4 and concluded that the Shawangunk is Salinan. He seems to have based his opinion upon (1) the conditions of overlap in a transgressing sea, (2) the existence of a marked unconformity at its base, indicating the lapse of a long time for folding and erosion since the Ordovician,5 and the nonfossiliferous character of the strata, suggesting the aridity of the Salina.6 J. M. Clarke accepted Ilartnagel’s correlation, fortifying his opinion by the discovery of numerous Eurypterids in the black shale in the Shawangunk which he . . .