PHYSICAL HISTORY ' 355 



Williamson shale, whereas in none of the Clinton divisions does there 

 appear more than a mere fragment of the large and typical Eochester 

 fauna (about 230 species recorded; see 8 : li) ; 10 : 7; 13 : 1487-1489) ex- 

 cept in the upper Irondequoit, especially its "reefs." 



On the other hand, the sifting of the fauuules reveals a surprising in- 

 coherence faunally in the stratic units of tlie Clinton itself. There is 

 here ]io discernible "Clinton fauna'' in tlie sense in wliicli tliere is a Ham- 

 ilton fauna or a Naples fauna. A\^liilc intensive collecting may give 

 greater homogeneity to the stratic paleontology, the larger disconformi- 

 ties will ahvays isolate rather definite assemblages, as will be further 

 shown after the physical evidence for these disconformities has been pre- 

 sented. 



Physical History 



The straight-line correlations of figures 1 and 2 fail to bring out 

 vividly the diastrophic movements, with their resultant overlaps, often 

 alluded to above. To visualize these, and to bring together all the sec- 

 tions on a uniform scale, text figures 3 and 4 have been prepared. While 

 drawn to measurement with the same care as the plates, the sections have 

 been connected in these diagrams by smooth curves, so as to reconstruct 

 more nearly the actual strata. As a result, some things that before ap- 

 peared as difficulties now prove highly significant. For instance, the 

 apparent excess at the summit of the Red Creek section (see figure 1) 

 serves to locate an accessory syncline in figure 3 (section "6"). Simi- 

 larly the deficient thickness of the Reynales limestone at Ontario marks 

 a secondary anticline in figure 4 (section "2"). 



The strata in figure .3 are given the attitude they are believed to have 

 had approximately during Rochester time. The overlying formations are 

 then fitted over these in their proper thicknesses, in order to emphasize 

 tliQ great summit unconformity and the cuestas of firmer rocks over which 

 the Mesontaric sea transgressed eastward. 



i\.t the east a similar basal unconformity of the Oneida conglomerate 

 on the Ordovician shales has long been recognized, and it has been cor- 

 rectly argued (by Grabau and others) that the amount of summit erosion 

 of these shales demands a later age for the Oneida than pre-Medina or 

 (as some have even thouglit) Oswego. In short, here also was an east- 

 ward transgression. 



Next most striking is the cNidcnce of a post-Wolcott diastrophism — a 

 Avcak compression fi'om the east, produchig a marked syncline in the 

 region of Oneida Jjake, with its maximum at Lakeport (section "9"). 

 Simultaneously the bordering regions rose into the zone of wave-plana- 



