ANCIENT WATER LEVELS OP CHAMPLAIN-HUDSON VALLEYS 231 



Esopus creek, draining the southern field of the Albany claj^s, 

 shows less signs of this change of level, and its delta is one of the 

 marked recent alluviums of the Hudson river. 



On the other hand Roeliff Jansen kill, which comes in from the 

 southeast and enters the Hudson below Catskill from a region 

 of clays and, higher up, sands, has a broad reentrant mouth, 

 showing excavation at a preceding stage. 



The Catskill is a large stream with a narrow gorgelike mouth 

 in the clay terrace and possibly is not on its original path where 

 it joins the Hudson. 



Stockport creek is another broad creek valley now largely silted 

 up but indicating broad erosion below the present sea level, sub- 

 sequent to the deposition of the Albany clays. 



From the mouth of Patroon's creek at Albany 42° 40' north 

 latitude, the relation of side streams to the Hudson gorge changes 

 and above that point in the river the tributary streams have pro- 

 longed courses over the bed of the old channel. Lateral embay- 

 ment of the mouths of these streams no longer takes place, and 

 evidence of uplift or of excavation of the river bottom everywhere 

 manifests itself in the rock floor of the ancient gorge by the be- 

 havior of the main stream and its tributaries. 



If the northern Hudson valley is or has been rising and the 

 southern part of the vallej^ is or has been sinking, somewhere 

 between the two areas must lie a line of no change of level. It 

 has already been noted that a marked change in the character of 

 the side streams in their relation to the gorge and its fiorded 

 waters takes place at Albany which is near the head of tide. The 

 actual delta of the Hudson river, as pointed out by Hayden^ as 

 early as 1820, occurs in this part of the river extending from near 

 Albany southward probably as far as Coxsackie in tlie form of 

 alluvial islands and shoals with ever increasing swampy mud flats. 



It is presumable that the axis of rotation in the uplift of this 

 region coincides with the present head of the delta or the vicinity 

 of Albany, for, if this axis lay to the south of this point, marks of 

 uplift in the side streams should appear farther south than they 

 do and, if the axis lay to the northward at an appreciable dis- 

 tance, marks of depression in the mouths of side streams should 

 manifest themselves instead of the signs of apparent uplift. 



^H. H. Hayden in Geological Essays. Baltimore. 1820. p. 35. 



