BOTANICAL CONTROL ON BANDING CHARACTER IN 2 NEW-ZEALAND COAL BEDS

Two New Zealand coal beds were examined using a palaeobotanical approach to determine controls on banding characteristics. The Morley (Cretaceous) coal is thickly (-5 to -1 phi or 32 to 2 mm) and well (> 25%) banded whereas the Brunner (Eocene) coal is essentially non-banded. Palynological analyses indicate that the Morley was formed from a gymnosperm-dominanted vegetation with a secondary component of angiosperms. In contrast, the Brunner was dominated by angiosperm vegetation with only a minor component of gymnosperms. However. it was found that any (xylite/vitrain) bands > 1 mm in either coal bed were comprised exclusively of secondary xylem of probable gymnosperm origin. The presence of (gymnosperm) wood (i.e. secondary xylem) forming the larger bands in both coals can be related to the relative resistance of this material to chemical and physical decay as compared to all other plant tissues. An absence of angiosperm wood in either the Morley or Brunner coal beds may be the result of the relative chemical degradability of angiosperm wood as compared to gymnosperm wood. Alternatively, angiosperms in either of the two palaeo-mires may have been shrubby and thus did not produce abundant woody tissue. In either case. the banded nature of the Morley coal bed is the result of the presence of gymnosperm wood and the non-banded nature of the Brunner is the result of being dominated by a flora (angiosperm) which is easily degraded.