Hancox, G.T. 1973 Geology and stability of the Pillars of Hercules. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 154 9 p.
Abstract: This report has been written at the request of the Nature Conservation Council who were concerned about the possible effects of the reduced water flows, resulting from the proposed Rangipo Power project, on the stability of the Pillars of Hercules. The geology of the area is outlined and the question of stability is discussed. Three figures accompany this report. (auth)