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NEW YORK STATE MUSEUM 



of thrust faulting- are here absent. In many places the close 

 proximity of folded g'neiss and overlying quartzite show the great 

 discordance in the dip of the two and less distinctly, though plainly, 

 in that of the strike. In places the two are so near that for all 

 practical purposes we are dealing with the actual contacts. The 

 relationship presents the aspect of an overlapping sea. Leaving the 

 gneisses at the south, one successively passes over the quartzite 

 and overlying limestones northward until lost in the close folding- 

 there prevailing. Erosion has greatly trenched the comparatively 

 soluble limestones of the Fishkill belt and has planed these strata 

 down nearly to a common level across the faults and folds. The 

 confusion resulting does not .conceal the substantial thickness of the 

 limestone strata and the great thickness of the slates and schists 

 of the Hudson valley to the northward only strengthens the con- 

 viction that they, with the limestones, once covered the tops and 

 filled the valleys of the Highlands over which they were carried 

 by an overlapping sea that progressively advanced over a subsiding 

 Precambric land mass. 



It is proposed in the later report to discuss in this connection 

 the occurrence of scattered masses of the younger rocks met With 

 in tiie Highlands and to suggest explanations for these occurrences. 

 It is purposed, also, to discuss the significance of the great block 

 fault south of the Highlands, which has dropped the younger rocks 

 of southeastern New York and the shattering which the Highlands 

 mass received from the forces producing this and other faults. 

 Some treatment will necessarily be given to the proposition that a 

 combination of forces, acting as a gigantic couple, the resultant of 

 the westward tangential pressures operated with the Adirondack 

 Precambric buttress to induce strike and transverse faulting of an 

 exceptionally violent sort in the powerfully elastic rocks of the 

 Hudson valley. 



Highlands of the quadrangle. The general petrography and 

 stratigraphy point to a Precambric sedimentary series with a Pre- 

 cambric intrusive sill, or bathylith, and some apparently later in- 

 trusions. The discovery of an altered limestone interbedded with 

 the gneisses, the heterogeneous character of the gneisses them- 

 selves and the occurrence of repetitions within them of certain 

 rock types, as well as. apparently, some plainer evidence of bed- 

 ding, are taken as the principal evidences of a sedimentary origin. 

 Microscopic evidence will be presented. No graphitic strata have 

 been noted. The structural features belong both to Precambric and 

 later time. Later deformations have been superimposed on earlier 



