GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 345 



though the slopes were steeper on the southeast. It was prob- 

 ably not till the end of Mesozoie time that the peneplain on the 

 sedimentary rocks was completed, the Catskills alone remaining 

 as remnants of the higher lands which were almost entirely re- 

 moved by erosion. That this peneplanation did not necessarily 

 include the old land will be clear from the discussion of the 

 manner of formation of the peneplain. Nevertheless we may 

 safely assume that these harder crystalline rocks also suffered 

 considerable erosion during the interval from the end of the 

 Paleozoic to the beginning of the Cenozoic (Tertiary) time. Some 

 portions indeed may actually have been reduced to peneplain con- 

 dition, as was the case with the crystalline rocks of New Eng- 

 land. Even the folds of the Appalachians were worn down till 

 that region of varied rocks was reduced to a comparatively level 

 portion of the great Cretacic peneplain, with the rivers lazily 

 wandering across the region without regard to the underlying 

 rock structure. 



With the beginning of Tertiary time the whole of the north- 

 eastern continent appears to have been elevated, whereupon all 

 drainage lines at once became revived and began actively to cut 

 valleys in the upland plateau. 



There is reason for believing that the land stood very much 

 higher at the beginning of the Tertiary than it does at present. 

 If the slope of the surface of the peneplain in this region was 

 northward at that time as it is now (judging from the gradual 

 northward decrease of altitudes) it is easy to understand how 

 such rivers as the Schoharie could begin to flow northward, and 

 cut a valley such as we find it, across the strata. But there ife 

 evidence which leads us to suppose that the surface of the pene- 

 plain, if not horizontal, was sloping so nth westward.^ If this was 



^The evidence for this is found in the apparent course of the preglacial 

 streams which carved the vklleys of the present Lakes Ontario, Erie and 

 Huron. The Tertiary consiequents of this region flowed in all probability 

 southwestward into the Mississippi gulf as did the Cretacic consequents. 

 For a disc^ision of this problem see the author's Guide to the Geology 

 of Niagara Falls, etc. and a paper entitled " Physical Geology of Central 

 Ontario " by Dr Alfred W. G. Wilson. Can. Inst. Trans. 1901. 7 :139-86. 



