Heavy minerals and the provenance history of Waitemata Basin sediments (early Miocene, Northland, New Zealand) 

Hayward, B. W.; Smale, D. 

1992 

 

 

Article in journal 

Census data from 100 heavy mineral samples from the early Miocene Waitemata Basin (81 samples) and its potential source rocks (19 samples) from Auckland and southern Northland, New Zealand, were analysed by cluster analysis, multidimensional scaling, and factor analysis. These analyses give rise to seven groups, each characterised by a distinctive mineralogy (factor): (1) dominated by clino-pyroxene plus magnetite, from a Miocene andesitic provenance; (2) dominated by ilmenite plus zircon and apatite, from a Mesozoic greywacke (Waipapa) and Paleogene sedimentary (Motatau, Mangakahia) provenance; (3) dominated by hornblende, from a Miocene volcanic or Cretaceous igneous (Tangihua) provenance; (4) co-dominated by horn-blende, magnetite and ilmenite, from a Tangihua provenance; (5) dominated by semi-opaque debris plus ilmenite, from a Waipapa provenance; (6) co-dominated by biotite and ilmenite, from a mixed Miocene rhyolitic, Tangihua and Motatau provenance; and (7) dominated by orthopyroxene plus clinopyroxene, from a two-pyroxene andesite provenance. Using these provenance interpretations for the heavy mineral groups, in conjunction with their stratigraphic and geographic distributions, we deduced a model for the paleogeographic and provenance history of the Waitemata Basin, and refined traditional models for the basin. Basal shallow marine sediments were derived exclusively from local Waipapa basement. Following rapid basin subsidence, two discrete sediment sources contributed to the older parts of the mid-bathyal, turbidite basin. These sources were a Cretaceous-Paleogene igneous and sedimentary source (Northland Allochthon) west of central Kaipara (for East Coast Bays and Paremoremo facies), and a contemporaneous volcanic source in north Kaipara or located beneath inferred basement nappes of the Whangarei area (for lower Pakiri facies). Younger parts of the central basin (Blockhouse Bay, Cornwallis, Timber Bay, and upper Pakiri facies) had a single Kaipara source area with a mixture of Northland Allochthon igneous and sedimentary rocks and contemporaneous andesitic volcanism. Another large active andesitic volcano, located west of Auckland, provided increasing amounts of sediment, firstly as sporadic submarine debris flows (Parnell Grit), and later as a broad volcaniclastic apron around its lower slopes. (auth) 

 

nzms262 03; waitemata basin; waitemata group; statistical analysis; paleogeography; lower miocene; auckland; heavy minerals; stratigraphy; northland; provenance; factor analysis; waitakere group; models; sediments; Biogeophysical; miocene