Word Study
niagara period
CIDE DICTIONARY
niagara period,
A subdivision or the American Upper Silurian system, embracing the Medina , Clinton , and Niagara epoch . The rocks of the Niagara epoch, mostly limestones, are extensively distributed, and at Niagara Falls consist of about eighty feet of shale supporting a greater thickness of limestone, which is gradually undermined by the removal of the shale. See Chart of Geology. [1913 Webster]
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