Bowen, F. E. 1964 Geology of Ohai Coalfield. Wellington: Department of Scientific and Industrial Research. New Zealand Geological Survey bulletin 51 203 p.
Abstract: The Ohai Coalfield lies in a depression extending slightly north of west from Wairio, on the western edge of the Southland Plains, to Birchwood Village, on the eastern side of Waiau Valley, some 50 miles north-west of Invercargill. To the north the depression is bounded by Wairaki Downs and to the south by Longwood Range. The coalfield makes up about 40 square miles of the area represented by the Wairaki and Morley sheets of the National one mile series of topographic maps. It includes parts of Wairaki and Wairio survey districts. The bulletin presents in detail the geology and resources of the coal measures, the older rocks being described only in enough detail to give a picture of the geological setting of the coalfield. Geological investigation of a coalfield is not completed until all the coal is exhausted, and no report can be up to date for long. The present work is based predominantly on informtion obtained up to the end of June 1953, with minor additions up to the end of 1955; the mine workings shown on the accompanying maps are as they were in June 1953. (auth)