REPORT OF THE STATE PALEONTOLOGIST 1901 637 



purpose. A slight transgression in Normans kill time is not 

 taken into account. 



Except around certain areas, composed of precambric rocks 

 and supposed to have been islands^notably the Adirondack^ of uppercambric 



limestone 



New York and a similar though probably less elevated area lying 

 mainly in Wisconsin — where the deposits were arenaceous, the 

 Upper Cambric sea laid down great beds of limestone. These 

 limestones are chiefly dolomite, and, in this case, indicate 1) re- 

 moteness from steep shores of the areas receiving them, 2) con- 

 siderable depth of water, which may explain the unusual paucity 

 of animal remains contained in them, and 3) chemical precipita- 

 tion as the main source of the matter composing them. 



As far as we can learn, it is onlv in the regions where Upper Beekmantown 



' *> ° rsr limestone 



Cambric deposits are decidedly arenaceous, as in New York, that 

 there is any marked distinction between them and the succeed- 

 ing strata of the Beekmantown age. Where they are made up 

 of limestones, like the Shenandoah and Knox formations of the 

 Appalachian valley, the Arbuckle limestone of Indian territory, 

 and the Pogonip limestone of Nevada, it appears that sedimenta- 

 tion and probably subsidence continued with little, if any, 

 marked interruption from practically the beginning of the Upper 

 Cambric to the close of the Beekmantown. 



The close of the Beekmantown, however, marks the inaugura- 

 tion of a new arrangement in eastern North America. First, a 

 fold was developed nearly parallel with and presumably Era of foIdin £ 

 a little within the western border of the original Lower 

 Cambric trough; second, another fold, that we have already 

 alluded to as having emerged early in Middle Cambric time, 

 and that was now only accentuated, and reemerged, arose 

 along a line marked in the south by the present western out- 

 line of the Ocoee series of rocks and in the north by the Green 

 mountains of Vermont. Though these folds extended appar- 

 ently without serious interruption from Alabama to and far 

 beyond Quebec, it is doubtful whether the trough bounded by 

 them was ever again entirely submerged subsequent to Beekman- 

 town time. Between them, the western one in the southern and 



