Northland Allochthon

Cluster and Canonical Correspondence Analyses were used to group 52 early Miocene (Waitemata Group) benthic foraminiferal faunas into eight associations and relate them to proxies for paleobathymetry and bottomwater energy.Modern Analogue Technique (MAT) was used to estimate the paleodepth of each fossil fauna by comparing their generic composition with 371 modern New Zealand faunas. MAT estimates are mostly consistent with, but no more precise than, those inferred by conventional subjective means. MAT estimates could be improved by broadening the modern database. The less precise paleodepth estimates for outer shelf and bathyal faunas were improved using the known upper depth limits of several key bathyal taxa. The combined use of MAT and conventional methods is advocated to provide the most robust paleoenvironmental interpretations.The paleobathymetry estimates are consistent with previously inferred regional subsidence during formation of the Waitemata Basin. The faunas document the submergence of a land with up to 100 m of rolling relief, with initial creation of both sheltered bays (Elphidium and Melonis associations) and exposed coasts (Amphistegina and Cribrorotalia, Gaudryina, Cibicides associations). Dysoxic faunas (Nonionella dominated) provide evidence for the accumulation of fine sediment on the quiet floor of several sheltered, deeper water inlets (20-40 m). As subsidence continued, the former ridge crests became islands and finally disappeared, coincident with cessation of coarse terrigenous sediment supply. Paleobathymetry estimates imply that several coarse, shallow-water gravel or shell hash units slid down the submarine slopes of these small islands to be interbedded with mid-outer shelf sediment (with Bolivina and Cibicides dominated faunas). Aperiod of sediment starvation (hiatus or thin mudstone) ensued: in the south, it spanned an interval during which the basin subsided from c. 150 m down to >400-500 m; in the north, it lasted until the basin floor reached lower bathyal depths (c. >1700 m, OridorsalisNodosaria association), before sand turbidites flowed in from the northwest.

Section: Tectonic Settingmentioning

confidence: 99%

Foraminifera‐based estimates of paleobathymetry using Modern Analogue Technique, and the subsidence history of the early Miocene Waitemata Basin

Hayward¹

2004

“…1), and these are thought to be at or near its southern limit (Isaac et al 1994). However, it has been suggested that the allochthon extends beneath the Waitemata Group, as far south as Waikato Fault (Ballance & Sporli 1979), and that it may be present beneath the Waitemata Group in the Karaka 1 well, drilled on the Manukau Lowlands (Hayward 19821 (Fig. 1).…”

Section: Southern Extent Of the Northland Allochthonmentioning

confidence: 99%

Late Eocene‐Oligocene Te Kuiti Group at Mount Roskill, Auckland, New Zealand

Edbrooke

Crouch

Morgans

et al. 1998

Vitrinite reflectance measurements indicate a lignite rank for coal fragments collected from the coal measures, and suggest a maximum burial depth of c. 800 m. Six Te Kuiti Group samples examined for palynomorphs and foraminifers gave ages ranging from Runangan to early Whaingaroan and show a transition from a predominantly terrestrial late Eocene environment to a shallow marine setting in the early Oligocene. This result helps substantiate previous inferences about the continuity of Te Kuiti Group deposition between Northland and Waikato, and supports the suggestion that the southern limit to the Northland Allochthon lies north of Auckland.

“…The North Cape, Whangarei and Auckland 4-mile geological maps of the 1960s showed isolated, small areas of 'Onerahi Formation' emplaced over younger strata, but these maps and the East Cape sheet predated recognition of the widespread overthrust and imbricated nature of much of the Cretaceous and Palaeogene strata (Stoneley 1968;Ballance & Sporli 1979). The Kaitaia, Whangarei, Auckland and Raukumara QMAPs portray the extents of the Northland and East Coast allochthons and show that, on a regional scale, they can be resolved into mappable sub-units based on age and lithology ( colour of allochthonous units provides a unifying identity.…”

Section: The Northland and East Coast Allochthonsmentioning

confidence: 99%

The QMAP 1:250 000 Geological Map of New Zealand project

Rattenbury¹,

Isaac²

2012

In 1994 the QMAP 1:250 000 Geological Map of New Zealand project began with compilation of the Dunedin sheet. Nearly 18 years later, publication of the Hawke's Bay sheet marks the completion of all 21 maps. The adoption of geographic information systems (GIS) software for data capture, data management and map production has not only produced high cartographic quality maps, but also built the attribute-rich, nationally consistent QMAP GIS spatial database. The project cost about NZD $24M, and the results are now being used by government, industry and research organisations across infrastructure, geological hazard, resource and environmental areas. QMAP has added significantly to general knowledge of New Zealand's geological composition and history due to new discoveries and validation of concepts. Notable advances include work on the allochthons of Northland and East Coast; rationalisation of the Taupo Volcanic Zone and East Coast stratigraphic successions; differentiation of the Torlesse basement terranes; clarification of the transition from Otago Schist to Alpine Schist; determining the complex spatial and temporal history of igneous intrusions in Fiordland and Stewart Island; and mapping Quaternary sediments by oxygen isotope stage and depositional processes.