REPORT OF THE STATE PALEONTOLOGIST 1902 1031 



tion is largely a repetition of that of 1838. He recognizes three 

 formations overlying the Hudson river beds, viz (1) the Water- 

 lime group, including the Tentaculite limestone (Manlius), (2) the 

 Catskill shaly limestone (New Scotland), and (3) the upper, 

 Scutella, or Sparry limestone (Becraft). The Coeymans and 

 Kingston were not differentiated from the limestones respec- 

 tively underlying each, and the higher strata were not recog- 

 nized. He determined the essential basin-shaped structure of 

 the mountain, and the unconformity between the lowest bed of 

 the series, and the underlying tilted and eroded Hudson river 

 strata. This unconformity is depicted in his section 6, which 

 furthermore illustrates with section 4, what he believed to be a 

 series of tilted fault blocks. This structure was undoubtedly 

 suggested by the numerous cuestalets which characterize the 

 outcrops of the New Scotland, and to some extent the other 

 beds also. The steep infaces or fronts of these erosion ridges 

 and the surface slopes of their tops, which follow the dip, have 

 all the aspect of the corresponding faces of slightly tilted fault 

 blocks [fig. 1, a, b]. Mather also gives a section of the south- 

 east end of Becraft mountain, which shows the overturned strata 

 on the east. 



Fig. 1 Diagram illustrating the detailed structure of parts of Becraft mountain: a, as in- 

 terpreted by Mather; b, as actually existing. 



In 1846 Emmons 1 gave a section of the southeastern end of 

 Becraft mountain, showing a conformable relation between the 

 Hudson river and overlying waterlime. He also speaks of a 

 mass of Oalciferous sandstone supported by the Taconic slate. 

 This refers probably to the hill of Burden conglomerate opposite 

 the center of the eastern face of the mountain. 



In 1858 Rogers 2 mentions the unconformity at Becraft, which 



he states he discovered in 1837. He says : 



The lower Helderberg or Pre-meridian rocks are seen in hori- 

 zontal stratification in the hill, while the Hudson river slates 



1 Agriculture of New York. 1846. 1 :136. 



2 Geology of Pennsylvania. 1858. 2 :785. 



