Definify.com
Webster 1913 Edition
Niagara period
Ni-ag′a-ra pe′ri-od
.(Geol.)
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
.