Structural divisions of eastern North Island

By: Moore, P.R. (DSIR, New Zealand Geological Survey. Lower Hutt).
Contributor(s): DSIR, New Zealand Geological Survey. Lower Hutt.
Material type: materialTypeLabelBookSeries: Record / New Zealand Geological Survey ; no. 30.Publisher: Lower Hutt : New Zealand Geological Survey, 1988Description: 24 p.ISSN: 0112-465X.Subject(s): STRUCTURAL GEOLOGY | STRATIGRAPHY | NORTH ISLAND | EAST COAST | CRETACEOUS | PALEOGENE | UNCONFORMITIES | NOMENCLATURE | IGNEOUS ROCKS | FAULTS | FACIES | NZMS262 05 | NZMS262 07 | NZMS262 08
Incomplete contents:
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.)
In: Record / New Zealand Geological Survey
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JOURNAL JOURNAL WELLINGTON
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STACK NO. 30 1988 1 Available J011623

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.)

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