It is likely that the entire Hog's Back Formation is of Chazyan age and that Chazyan-Blackriveran boundary coincides with the Hog's Back-Pamelia formation contacts.
Hog's Back-Pamelia Formation contact
This picture shows an upthrusted block of the Hog's Back Formation in the front and the Pamelia Formation is the sediment in the background. It is somewhat difficult to see the Pamelia in this photo but there are many others throughout the pages in which it can be observed more closely. Hog's Back Falls, Ottawa
The Rockliffe and Hog's Back formations were deposited during a northwestward advancing Middle Ordovician [Chazyan] transgression. Siliciclastic detritus eroded from Precambrian highs bordering the northern and western margins of the Chazyan shallow sea and dominate facies along the western sites of the basin (Salad Hersi 1998).
Lowville-Chaumont Formation contact
This is a photo of the Lowville(L)-Chaumont(C) contact taken from Salad Hersi (1998) defined by Lowville beds with rubbly, eroded texture overlain by thick beds of the Chaumont Formation. Hammer is 25cm long. Cornwall quarry, Cornwall.