344 G. H. CHADWICK STRATIGRAPHY OF NEW YORK CLINTON 



low- water deposit,^ ° and its basal contact at Eochester suggests to the 

 writer a disconformity, probably the same as that at Blackstone's. In 

 any case the bed marks the introduction of a varied fauna, much of which 

 yet remains to be studied. It includes : 



ButhotrGpliis gracilis ?i^cmicosGinium cUntoni (3 :50) 



Peronosporites glodosus ''Orthis" trinucleus (3 : 74) 



Peroiiosporites minutus Stroplionella patenta ? 



Peronosporites ramosus Hyattidina conyesta 



Enterolasma caliculus ? Coelospira nitens C'hemispherica'' ) 



Ganinia MlateraUs Ccelospira plicatula 



Ptiloporella ? sp. Botryocrimis plumosus 



Phwnopora constellata (9 : PI. 3) Tentaculites minutus 



Phwnopora ensiformis ? Actinoceras vertehratiim 



The basal shale at Niagara likewise holds Coelospira nitens and pli- 

 catula (10: 7; 12: 309) and Pterinea (?). We can not at present feel 

 sure what this shale represents, but it is surely not the Maplewood 

 ("Sodus'^ of Rochester). 



DARK SHALE IN LAKEPORT WELL 



It would be hazardous to draw any parallel between this and the bed at 

 N"iagara just mentioned. Since it is not known to outcrop in New York, 

 it can not be named. 



RE TN ALES LIMESTONE 



If the shale equivalent of the Lower Clinton limestone of Rochester 

 carries any Pentamerus at its sole exposure in the town of Wolcott, 

 namely, at the old ore bed on Bear Creek, this fact could hardly have 

 escaped such acute observers as Hall and Yanuxem. Hall distinctly 

 mistook this stratum there for the upper — that is, Williamson — shale 

 (2:75).^^ The true Pentamerus . limestone of Wolcott furnace, which 

 must inherit the name Wolcott limestone, is a higher bed. The only 

 complete exposures o*f the lov^er limestone, in its typical western develop- 



10 The problem of the origin of these ores has been treated by Smyth in Am. Jour. Sci. 

 (1892), vol. 43, pp. 487-496 (Am. Geol., vol. 10, pp. 122-124). All the ores seem to be 

 marine, or at least to contain marine material, perhaps reworked. They must, however, 

 have accumulated exceedingly slowly, each through a long time interval, during which 

 the supply of ordinary clastic sediment was nearly suspended. A certain amount of 

 wave-ablation and of concentration of previous deposits may also have gone on, remov- 

 ing the finer particles and converting the coarser into ore — in the landward zone by 

 oolitic coating of sand grains ; in the more open waters by ferruginous replacement of 

 calcareous fragments. These processes constituted pauses in the ordinary sedimentary 

 record, perhaps of the type that Professor Barren calls a "diastem," and they are from 

 time to time contemporary with diastrophic readjustments. 



11 In his second annual report, 1838, p. 327, Hall reports the Wolcott ore bed as 

 "immediately below the Rochester shale." 



