This Section includes all the islands below Fredrick Sound, as well as the mainland south of the Stikine River corridor below the permanent snowfields in southeast Alaska. Most of the area is rugged mountains with many broad, U-shaped, glaciated valleys which terminate as fjords at tidewater. Tidewater glaciers are infrequent in this Section. Lithology and Stratigraphy. The geology is very complex, consisting of volcanic islands and continental fragments of the Craig subterrane, Admiralty subterrane, and Taku terrane.
Most rock types are Jurassic to Mesozoic deposits of sedimentary and volcanic rock types.
Many of the assemblages have been metamorphosed, faulted, or folded, and the trending of most faults is northwesterly. Predominant soils are Terric Cryohemists, Humic Cryorthods, Humic Lithic Cryorthods, and Andic Humicryods. Most of the soils on the steep slopes are formed in colluvial or landslide materials. Poorly drained depressions or low-lying areas are peatlands. Potential Natural Vegetation.