Multiple regression analysis is applied to the study of facies change in the Ordovician lower Cobourg limestone in northwestern New York and southern Ontario. A linear surface is fitted to the scattered outcrop data. The results indicate an increase in the lower Cobourg calcilutites north-northeastward along the outcrop east and north of Lake Ontario and an accompanying decrease in the calcarenite texture. This is interpreted as a winnowing-out of the calcareous muds into the deeper water on the north-northeast.

Preferred orientation of lower Cobourg pararipples indicates that northeast-southwest currents predominated. Progressive change in mean pararipple wavelength tends to support the northward increase in depth of water obtained from the texture analysis.

A synthesis of the linear regression results for Shoreham, early Denmark, and lower Cobourg textural data in the northwestern New York area denotes maximum submergence in early Shoreham and minimum submergence around early Denmark. Lower Cobourg seas were slightly deeper than early Denmark.