trenton period

from The Collaborative International Dictionary of English v.0.48

Trenton period \Tren"ton pe"ri*od\ (Geol.)
   A subdivision in the lower Silurian system of America; -- so
   named from Trenton Falls, in New York. The rocks are mostly
   limestones, and the period is divided into the Trenton,
   Utica, and Cincinnati epochs. See the Chart of {Geology}.
   [1913 Webster]