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The western-most region of Taranaki Basin, the Western Platform, has a stratigraphy which permits subdivision into major seismic units. The reflectors separating these units are easily identifiable. Each of the units and reflectors has typical reflection characteristics which are often correlatable with the lithology of the unit. Lateral velocity variations, caused by lateral deposition and compaction variations in prograding sequences, area major problem in developing depth conversion models for this region. Analysis of travel time data from wells shows that velocity variations in both the Oligocene-Miocene and Pliocene-Pleistocene sequences are predictable from the thickness variations of the units (and hence from interval travel times). The imerval velocity variations of the Paleocene-Eocene transgressive sequence are dependent on the overburden history and lithology of the unit.

The basement structure and sedimentary history of the continental shelf east of the northern section of North Island, New Zealand is interpreted from geophysical data collected by petroleum companies. Interpretation of magnetic data shows the basement to be composed of both igneous and nonigneous rocks in the vicinity of the Coromandel Peninsula and Great Barrier Island; further north the basement is almost entirely nonigneous. From seismic reflection data, basement in the region can be seen to have undergone extension, being faulted into a series of fault-angle depressions and grabens. Sea-floor expression indicating continued development of the fault-angle depressions is found locally, especially in the Tauranga Harbour-Cuvier Island region.Outside the Hauraki Gulf, the sedimentary section overlying basement is separated into two units by an unconformity of unknown age. The lower unit is probably late Tertiary -Quaternary sediments and the upper unit is probably late Quaternary sediments. Within the Hauraki Gulf, the poor quality of seismic reflection data precludes analysis of the sedimentary section.

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