Oblique aerial view of the southern end of Kayak Island, Alaska, a narrow, 32-kilometer-long bedrock island that trends offshore in a southwesterly direction. This is one of the most striking geomorphic features on the classic leading edge rocky coast of southern Alaska. Structurally, this island is located in the Kayak Island zone, a southwest trending structural unit that occurs beyond the western margin of the Yakutat terrane, running parallel to the major thrust fault along the border of the Aleutian trench (Winkler, et al. 1992).

Probably the most striking geological feature on Kayak Island is the prominent knob at the southwest end of the island (clearly visible in this photograph) that consists of very pale gray dacite plug complex that forms the landmarks of Cape Saint Elias and Pinnacle Rock at the seaward end of the Island (Plafker, 1974). The dacite is very dense and hard, nd is conspicuously jointed. It has a microgranitic and porphyritic texture, and consists of about 35 percent plagioclase, 35 percent quartz, 25 percent orthoclase, and 5 percent relict brown hornblende and biotite. It has sharp, nearly vertical contacts with adjacent dark-gray argillaceous rocks of the Yakataga and upper Poul Creek Formations that have been hornfelsed for at least 100 m around the intrusion. This dacite plug intrudes the upper part of the Yakataga Formation and must be at least as young as Miocene, more likely Pliocene, because it has been emplaced after the enclosing strata were deformed (Winkler and Plafker 1981).

This photograph, taken in the summer of 1970 by Miles O. Hayes, was one of the featured images in the tone poem, Suzanne's Lament.

LITERATURE CITED

Plafker, G., 1974, Geologic map of Kayak and Wingham Islands, Alaska. U.S. Geological Survey Open-file report 74–82.

Winkler, G.R. and Plafker, G., 1981. Geologic Map and Cross-Section of the Cordova and Middleton Island Quadrangles, Southern Alaska. U.S. Geological Survey Open-file Report 81–1164.

Winkler, G.R.; Plafker, G.; Goldfarb, R.J., and Case, J.E., 1992. The Alaska Mineral Resource Assessment Program: Background Information to Accompany Geologic and Mineral-Resource Maps of the Cordova and Middleton Island Quadrangles, Southern Alaska. USGS Circular 1076, 20p.