Isaac, M.J. 1985 New Zealand Coal Resources Survey : coalfield geology and coal prospects in Northland. Lower Hutt: New Zealand Geological Survey. Record / New Zealand Geological Survey 4 30 p.
Abstract: At Kawakawa, Hikurangi and Kamo, Late Eocene Kamo Coal Measures are present at depth beneath allochthonous Late Cretaceous to Oligocene covering strata. Thirteen exploratory boreholes were drilled in eastern Northland for the New Zealand Coal Resources Survey funded by Mines Division, Ministry of Energy, between October 1982 and July 1983. The major objective was to investigate the possibility of further areas of concealed Coal Measures separate from those mined in the past. Many of the drillholes passed through the allochthonous strata into the younger Late Eocene to Oligocene beds, but only four found Kamo Coal Measures, and none found workable coal. Results indicate that the full Whangarei Limestone - Ruatangata Sandstone - Kamo Coal Measures autochthonous sequence is of restricted extent. In many areas its only equivalent is 1 to 14 m of marine glauconitic sandstone and limestone. Stratigraphy, drilling results and coal prospects are discussed area by area. The chances of finding a further deposit of several million tonnes of recoverable coal are assessed as poor