NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 13 



It is a truth of wide application that the topography of any region 

 is intimately dependent on its geologic structure; and this truth 

 finds ready illustration within this area. In the following pages 

 attention will be directed more than once to this relationship. 



GEOLOGY 



The sedimentary rocks comprise shales, sandstones and con- 

 glomerates. They are generally red in color but not always. 

 Some of the sandstone layers are gray and brown, and occasion- 

 ally black or dark green beds of shale occur, but the great mass 

 of the formation is a dull red color, so monotonous in the unchang- 

 ing succession of layer after layer that differentiation on this 

 basis is well nigh impossible. 



The character of the rocks and their relations to the larger area 

 can best be understood by a comparison with the section along 

 the Delaware river in New Jersey, where they are well shown. 

 Here it is possible to divide the beds into three groups. At the 

 base there is a succession of 1) coarse, more or less disintegrated 

 arkose conglomerates, 2) yellow, micaceous, feldspathic sand- 

 stone, 3) brown red sandstones or freestones, and 4) soft, red 

 argillaceous shales. These are interbedded and many times re- 

 peated, a fact which indicates rapidly changing and recurrent con- 

 ditions of sedimentation. The characteristic beds of this sub- 

 division are the arkose sandstones and conglomerates. I have 

 used the term Stockton in connection with this group. 



Overlaying the Stockton beds, there is a group of hard dark 

 colored shales and flagstones, called the Lockatong beds. They 

 consist of 1) carbonaceous, thin splitting shales, 2) hard, massive, 

 black and bluish purple argillites, 3) dark gray and green flag- 

 stones, 4) dark red shales approaching a flagstone and 5) occa- 

 sional thin layers of highly calcareous shale. There are all grada- 

 tions between these somewhat distinct types, which are inter- 

 bedded and several times repeated in varying succession. The 

 presence of sun-cracks at all horizons shows that shallow water 

 conditions prevailed throughout the time of their deposition, 

 though the extreme fineness of the material indicates the absence 

 of strong currents or violent shore action. 



