The Upper Salmon River karst, Anticosti Island, Quebec, Canada

Anticosti Island is composed of medium- to thin-bedded carbonates of low dip and low relief. A joint set striking 110° displays great regularity and persistence. The island was glaciated during the Late Wisconsin but drift cover is thin because of marine over-wash. The principal karst extends along the joint set with 38 km2 holokarst area and 105 km2 allogenic catchment. Karstic features are kluftkarren, shafts, ponors and one regional spring. Hydraulic gradients are very low and the aquifer is phreatic but groundwater velocities exceed 35 m hr.−1 at low stage. The karst is believed to be of postglacial age, and expanding at a minimum mean rate of 1200 m per 1000 yr. along the master joint set.