Pg. 172. Portage or Nunda group. Present in New York and Pennsylvania. Is = Sherburne flags of Hall. Includes Cashaqua shale, Gardeau and Portage groups, and Sherburne flagstone and shale of reports. Relative position perfectly seen on Cayuga Lake. Underlies Ithaca group and overlies Genesee slate. [Age is Late Devonian.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1521).

The use of Nunda for Portage group was generally abandoned many years ago, Portage having both priority and usage in its favor. The New York State Survey and USGS both use Portage group and apply Nunda to the sandstone formerly sometimes called †Portage sandstone. G.H. Chadwick, however has recently adopted Nunda for the group and Portage for the sandstone. (See his papers in Pan-Amer. Geol., v. 60, 1933, and GSA Bull., v. 46, no. 2, 1935.) He includes in his Nunda group all beds from base of Ithaca to top of Wellsburg.
"Named for superior development along banks of Genesee River in district formerly included in town of Nunda, now Portage." (James Hall, 1843.)

Source: US geologic names lexicon (USGS Bull. 896, p. 1521).