NON-MARINE PROGRESSIVE OVERLAP 



629 



the marine, though in reality it is more a replacement of the one by the 

 other. The following diagram will make this clear: 



Figure 12. — Overlap Relation of marine and non-marine Beds. 

 EXAMPLES OF NON-MARINE PROGRESSIVE OVERLAP 



Chemung-Catshill. — A typical example of the last described type of 

 overlap is seen in the case of the Catskill and Chemung formations of 

 New York and the northern Applachians generally. Here the non-marine 

 Catskill begins in Portage time as the Oneonta, and is gradually but 

 progressively pushed westward and northwestward until it has reached 

 the very summit of the Chemung. Thus in the Ithaca region the red 

 sedimentation of the Catskill type does not begin until upper Chemung 

 time. In the Olean region farther west it begins in the Cattaraugus beds 

 above the Chemung (Devono-Carbonic transition). Thus, while the 

 Chemung is fully developed in western New York, it is absent in eastern 

 New York and Pennsylvania, where the Catskill type of sedimentation 

 alone occurs. Between these two points both are seen, the non-marine 

 always overlying the marine. This relationship is shown in the following 

 diagram : 



-V 



— V 



- V"; t - - - ~^- 



=^~k~irJ% 



— V 





4^s 



- — — - ---tL-^o/7- rnart'n e~~SS. 



N. — 



— >v 



— \ V 



— \ 



e m u /7 q ■ 

 — \ — \- 



: /7?q r/?ie 

 v— \ - \ 



- V - V 







X 



N- 



-x - 



N \ — 



-> - 



- -V- — 



"Nr~— - 



*\ — 



\- 





\ — 



> — \ 



\- 



— S ~ "x -^L.^, "C •=■ - "- VI-I- V^""->~ 



— V 



— \ 



— \ — \ - 



— \ > 



— \ 



— X 



N — 



■\ — ^ — \ — s-^^s.-^« — ~-^----~- 



Figure 13. — Overlap Relation of marine Chemung and non-marine Catskill Beds. 



The Pocono. — This is the .lowest of the Appalachian Lower Carbonic 

 formations and represents the continued non-marine sedimentation from 

 the Appalachians northwestward to the western Pennsylvania region. 

 The original easternmost extension of this formation, as of the preceding 

 and succeeding non-marine formations, has been removed by erosion; so 

 that we find at the present time only portions which originally were 

 accumulated at some distance from the highland which furnished the 

 material. 



