Coal resources of each coalfield are summarised in Tables 1 and 2, and given in detail in Tables 3 to 17. The thick, structurally complex Late Cretaceous and Tertiary sequences of the east coast of the North Island and northeastern South Island lack significant coal measures. Late Cretaceous coal measures in the Greymouth, Ohai and Kaitangata coalfields contain major coal resources in terrestrial sedimentary sequences deposited in a series of long narrow fault-bound basins. As the separation of the New Zealand region from Australia-Antarctica began, these basins subsided rapidly, and were filled with alluvial fan, fluviatile, and lacustrine sediments. The Pakawau Coal Measures in Northwest Nelson and the Broken River Coal Measures in Canterbury, which are also Late Cretaceous in age, have a limited extent on land, but petroleum exploration drillholes and associated seismic data suggests they have widespread development at depth offshore.
Coal measures form the base of a marine transgressive sequence.
The Waikato Coal Measures of the North Island and Brunner Coal Measures of Westland contain major coal resources, and early Tertiary coal is also found in Northland and many parts of the South Island. In the Greymouth and Ohai coalfields, Eocene coal measures overlie the Late Cretaceous coal measures, while in other areas they were deposited directly on the peneplained and often deeply weathered basement surface. As in the Late Cretaceous, syndepositional faulting influenced coal deposition, which was also partly controlled by basement relief. The initiation of a marine transgression in the latest Eocene meant that terrestrial coal measures were eventually overlain by marine beds, often at first deposited in shallow basins with restricted circulation. In some basins, great thicknesses of deeper-water marine strata were then deposited, and the coal measures deeply buried.