Many refs; 7 figs

Seven major structural blocks and two separate sub-belts are recognised in eastern North Island, based on differences in facies, structure, thickness, distribution of igneous rocks, and presence of unconformities in the Cretaceous-Paleogene sequence. The Neogene sequence is not considered. Structural blocks are largely, if not entirely, fault-bounded, and have probably been displaced considerable distances (10's of kilometres) relative to one another. Major faulting is largely post-mid Oligocene. The Cretaceous sequence in western parts of the region is generally finer-grained (mudstone-dominated), less deformed (mostly open-folded), and contains more local unconformities than in the east. Eastern areas are characterised by a Cretaceous flysch facies (locally conglomeratic), complex deformation, and relatively continuous deposition. The Whangai Formation (Haumurian-Teurian) is more calcareous in th east, but fewer differences are apparent in the overlying Eocene sequence. Igneous rocks of Early Cretaceous and Late Cretaceous-early Tertiary age, ranging from tholeiitic to alkaline in character, are more common in the east. Implications for petroleum exploration are briefly discussed. (auth.)