Abstract. Downstream changes in particle size that occur in the Waipaoa River, a 104-km-long gravel bed river in which rapid aggradation in the historic (post-1800) period was triggered by the conversion of native forest to pasture, are summarized in this paper. The textural data presented are unique for a field situation, not only because of the spatial resolution and extent of the sampling program but also because they provide information about the pattern of fining at different points in time. They are supported by equally comprehensive topographic survey data from which local rates of aggradation can be derived. Despite variability induced by lateral sediment inputs, there is an essentially continuous pattern of fining along the entire length of the river. Fining occurs in both the fine and coarse size fractions of the bed material. The highest rates of fining occur in the larger percentiles of the subsurface bed material and in the surface bed material. Downstream fining in the Waipaoa River appears to be a response to changes in flow hydraulics that are regulated by the concave configuration of the long profile. The fining gradient developed rapidly (in <45 years). It does not appear to be influenced by the rate of aggradation (nor the overall rate of sediment supply to the channel system), because, in the short term, aggradation has a negligible impact on the inherited form of the long profile.

The stratigraphy and sedimentology of the Paleocene-Oligocene sedimentary sequence of Taranaki Basin is reviewed using data obtained from exploration wells. Sixteen of these wells are sited in the Taranaki Graben, an infilled, downfaulted block extending westwards from the Taranaki Fault to the Cape Egmont Fault Zone. A further seven wells are sited on the Western Platform, which extends westwards from the Cape Egmont Fault Zone seaward to beyond the edge of the continental shelf.In the past, the lithostratigraphic nomenclature applied to the sequences encountered in the wells was adopted from adjoining onshore areas. Where existing names were inadequate, new names were created, but never formally defined.The term "Kapuni Formation" is an informal name for the Paleocene-Oligocene sandstone-coal measure sequence which was first encountered in the Kapuni-1 well. It is proposed that the thick sequence currently known as the Kapuni Formation be formally named the Kapuni Group. Kapuni Group is subdivided into four formations. From oldest to youngest they are Kaimiro Formation, Ornata Formation, Mangahewa Formation, and McKee Formation. A lateral, fully marine equivalent of the Kapuni Group is described.A further three formations are defined. The Whaingaroan marine mudstone (Kaiata Formation of Shell BP and Todd Oil Services Ltd) is here named the Turi Formation; the Whaingaroan-Waitakian calcareous siltstone sequence informally known as the lower Mahoenui Group is named the Otaraoa Formation; and the Waitakian limestone immediately underlying the Mahoenui Formation proper is here named the Tikorangi Formation.The stratigraphy of Taranaki Basin is compared with that of adjoining onshore areas to the north and south. Similarities are apparent and possible northern and southern correlatives are proposed.

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