Journal of Petroleum Geology, vol. 20(4), October 1997, pp. 427-458
©Copyright 1997. Scientific Press, U.K. All rights reserved.
RELATIONSHIPS BETWEEN HYDROCARBON GENERATION, COAL TYPE AND
RANK FOR MIDDLE EOCENE COALS, BULLER COALFIELD, NEW ZEALAND
C. M. Norgate+*, C. J. Boreham**, P.
J. J. Kamp* and J. Newman***
The Buller Coalfield in the northern portion of the Paparoa Trough (NW South Island,
New Zealand) contains a middle Eocene bituminous coal-bearing succession that exhibits
marked variations in both coal rank and type. The across-basin rank changes result from
differential late Palaeogene subsidence of the Paparoa Trough and subsequent inversion.
Superimposed upon coalification trends are down-seam variations in coal type, evidenced by
isorank variation in conventional chemical parameters. These type variations are not a
consequence of changes in maceral group proportions, which are dominated by vitrinite.