THIRD REPORT OF THE DIRECTOR I906 55 



grit plateau — it may be properly inferred that the Upper Siluric sea 

 of New York did not extend into the present area of the Rensselaer 

 grit plateau at any time except possibly in the Manlius age. In 

 regard to the latter, the problem is the same as in regard to the 

 Helderberg limestones in general which are exposed at Becraft 

 mountain and of which the Rensselaer grit might represent the 

 littoral facies. In favor of this view it may be said that both rest on 

 the same basis (Cambric and Lower Siluric slate) and that on ac- 

 count of the rising of the Taconic mountains in early Siluric time, 

 there may have existed a littoral facies of the Helderberg rocks to 

 the east. But this view is strongly opposed by the fact that the 

 Helderberg rocks do not show any indications of approach to a 

 littoral region at Becraft mountain, but retain the same lithologic 

 characters that they possess over a vast area. There would hence 

 have to be assumed an extremely abrupt and improbable change in 

 facies in the short distance of 20 miles from Becraft mountain to 

 the outlier at Austerlitz. An exception to this seems to be made by 

 the Oriskany sandstone, Esopus grit and Schoharie grit which not 

 only contain sand and grit at Becraft mountain and in the Helder- 

 bergs, but in some places as at Whiteport and Kingston, contain 

 conglomerate beds. It is altogether probable that the material of 

 these conglomerates was derived from the south and the Oriskany 

 sandstone is too thin a layer (30 feet) at Becraft mountain, to be 

 correlated with the thick mass of the Rensselaer grit (1400 feet). 

 It is, however, possible that the Esopus and Schoharie grits which 

 at Becraft mountain have a combined thickness of 300 feet and are 

 similarly barren in fossils, once continued northeastward into the 

 Rensselaer grit trough. Since they represent an invasion of the 

 sea that came from the south and spread northward in the direction 

 of the Rensselaer grit plateau, and the overlapping Rensselaer grit 

 is clearly the product of an invading, not a receding sea, it is a 

 question for consideration whether the Rensselaer grit was not 

 deposited in a long narrow embayment extending northward from 

 the Oriskany-Esopus-Schoharie grit sea of southern New York. But 

 in this case also, there is still to be explained the extremely rapid 

 change from the typical Esopus grit of Becraft mountain to the 

 red and green slates and coarse grits of the Austerlitz outlier, and 

 the fact that the Esopus grit is thicker southward (700 feet in 

 Orange county), and thins out toward Becraft mountain. The 

 regular succession of the various members of the Lower and 

 Middle Devonic in Becraft mountain with the same lithologic 



