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NEW YORK STATE MUSEUM 



thickness of the Rondout wateflime is I feet G inches. It rests 

 directly and unconformable on the Lorraine shales and is fol- 

 lowed conformably by normal Manlius with typical fossils. 



From the foregoing it becomes apparent that there was a 

 continuous northward and eastward transgression of the interior 

 or Mississippian sea from the beginning to the end of Siluric 

 time. The origin of the lime mudrocks forming the Avaterlimes 

 and the Manlius limestone needs a brief consideration. They 

 have been considered as chemical precipitates, but all the char- 

 acteristics of the rock are against such an assumption and point 

 rather to a clastic origin. Considering this origin as the most 

 likely, the lime mud must have resulted either from the grinding 

 up of organic deposits, such as shell heaps or coral reefs, or 

 through the mechanical erosion of earlier limestones. So far 

 the direct derivation of the lime mud from organic deposits has 

 little evidence to support it. It is true that there may still exist 

 coral reefs or shell heaps of this period which have not yet been 

 exposed by erosion, and that others may have been entirely 

 worn away. Yet in view of the fact that these deposits are 

 uniform over such wide areas and that no remains have been 

 found in them from which such lime flour could be derived, we 

 are hardly justified in entertaining this supposition. If on the 

 other hand we consider that these lime mudrocks were largely 

 formed from the lime mud derived from the Trenton and older 

 limestones, we must postulate (bat these limestones, which un- 

 doubtedly reached far up on the crystalline old land, 1 were 

 covered by Utica and Lorraine sediments at the end of Lorraine 

 time; that these silieions sediments were gradually eroded during 

 early Siluric time, and that at the beginning of the waterlime 



'The Trenton limestones may actually have covered the Adirondacks, but 

 Kemp is inclined to believe that this was net the ease, Cushing, in a 

 recent paper [N. V. State Mns. Bill. 77. L905. p.52 ei seq.] concludes that 

 there was a progressive overlap of the early limestones on the crystallines, 

 capped by Utica shale which may have extended to or above the summit 

 of the entire massive. Wilson cites several cases where Black river corals 

 grew mi the crystallines in the neighborhood of Kingston Ont. 



