538 GEOLOGY 



lating along the eastern border of Appalachia at this time, nor of 

 those about the other land areas. 



The Niagaran series. The Clinton formation overlies the Medina 

 conformably, but has a wider distribution. Westward, it extends 

 to Lake Huron and Indiana, and perhaps to the Mississippi. If 

 this is the case, it is represented by beds which have been classed 

 with the Niagara limestone. The formation occurs in the Appala- 

 chians as far south as Alabama and Georgia. The fossils of the 

 formation in the Appalachians are so unlike those of the interior, 

 as to lead to the inference that the sites of sedimentation in the two 

 areas were not freely connected. Beds of Clinton age have been 

 recognized in Nova Scotia and at a few other places northeast of 

 the United States. Marine sedimentation was probably continu- 

 ous here through the Ordovician and Silurian periods. 



The variations in the character of the Clinton beds in differ- 

 ent localities are significant. In the Appalachian Mountains, the 

 formation is largely of sandstone and shale. In western New York 

 and farther west, much of it is limestone. The limestone does not 

 mean that the water was necessarily deep, but rather that it was 

 so nearly free from clastic sediments that the shells, etc., constituted 

 the principal part of the deposit made. Shell-bearing life may be 

 just as abundant where sand and mud are accumulating as else- 

 where, but in this case the product is not limestone, but sandstone, 

 shale, etc., containing shells. Bryozoan reefs, resembling coral 

 reefs, occur in the formation in western New York. 1 



One of the notable features of the formation is its content of 

 iron ore, generally in the form of hematite (Fe 2 O 3 ). The ore is often 

 made up of small concretions which so resemble flaxseed in size and 

 shape as to have suggested the name " flaxseed" ore. Locally it is 

 known also as " fossil" ore from the abundance of fossils which it 

 contains. The ore is known at many points between New York 

 and Alabama, as far west as Wisconsin, and as far northeast as 

 Nova Scotia. The ore is interstratified with other beds of the 

 formation, and is usually believed to have been accumulated by 

 chemical precipitation in lagoons or marshy flats. 



Like the Oneida and Medina formations which preceded, the 



1 Sarle, Am. Geol., Vol. XXVIII, p. 282. 



