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Reassessment of Neogene tectonism and volcanismin North Island, New ZealandDavid Kear aa 34 West End, Ohope, Whakatane, New Zealand E-mail:Published online: 21 Sep 2010.

To cite this article: David Kear (2004) Reassessment of Neogene tectonism and volcanism in North Island, New Zealand,New Zealand Journal of Geology and Geophysics, 47:3, 361-374, DOI: 10.1080/00288306.2004.9515062

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New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 361-3740028-8306/04/4703-0361 © The Royal Society of New Zealand 2004

361

Reassessment of Neogene tectonism and volcanism in North Island,New Zealand

DAVID KEAR

34 West End, OhopeWhakatane, New Zealandemail: kear@xtra.co.nz

Abstract Reassessment of North Island Neogene tectonismidentifies three shorter, vigorous, tectonic events, whichseparate three longer periods of relatively consistent tectonicactivity and volcanism.

Waitemata Tectonic Event (26-25 Ma) establishedsouthwestward subduction beneath Greater Northland,creating the Northland Allochthon, and two belts ofsubsequent volcanism (23-16 Ma) with the Waitematasedimentary basin between.

Kiwitahi Tectonic Event (15-14 Ma) terminatedNorthland volcanism and triggered Coromandel and Kiwitahivolcanism, which migrated southwards in the same twobelts. Migration coincided with 200-300 km of transcurrentmovement along a now-abandoned Alpine Fault trace, whichalso transferred the subduction system, Cretaceous sediments,the East Coast Allochthon, Miocene pumiceous beds, andthe East Coast region southward. Before 5 Ma, c. 25° ofdextral curvature was imposed on the North Island, andrelative tectonic quiescence (with consequent intraplatevolcanism) extended southwards through Northland andSouth Auckland.

Kaimai Tectonic Event (5-2.5 Ma) halted volcanicmigration and imposed another 40° of curvature. That causedthe rotational rifting of the Central Volcanic Region, whichinitially tore away progressively along the Alpine Faulttrace, creating three successive volcanic zones - newlyproposed Mangakino (2+ Ma to 950 ka), newly proposedManawahe (950 to 400-350 ka), and previously namedTaupo (400-350 ka to today).

Keywords Alpine Fault; North Island; tectonics; volcanism;Northland Allochthon; East Coast Allochthon; CentralVolcanic Region; Mangakino Volcanic Zone; ManawaheVolcanic Zone; Taupo Volcanic Zone; Marshall VolcanicBelt; Searle Volcanic Belt; North Island Dextral Fault Belt;new structural names

INTRODUCTION

The North Island's Neogene tectonic activity and its relationto consequent volcanism have been reassessed, basedpredominantly upon onshore North Island geology. Six time

G03035; Online publication date 7 September 2004Received 10 December 2002; accepted 17 September 2003

intervals were involved—three longer ones, each with arelatively consistent tectonic regime, separated by threeshorter, more active, "tectonic events" (Kear 1994): theWaitemata (c. 26-25 Ma), the Kiwitahi (c. 15-14 Ma), andthe Kaimai (c. 5-2.5 Ma). During each event, a new anddifferent tectonic regime (and consequent pattern ofvolcanism) was imposed.

This paper follows an earlier one (Kear 1994). Itsobjective is not to create a new model, but to use moreeffectively existing, factual and verifiable onshore geologicaldata to produce maps and diagrams relating to North Islandtectonic/volcanic development during the Neogene. Somemaps and diagrams (termed "dynamic") allow the reader tovisualise movement by the inclusion of features as theyexisted at more than one time, or by implying movementbetween specific times. The basic methodology is that usedroutinely in the compilation of geological, isopach, andcomparable maps, where the option of no decision is notavailable. An example exercise is converting volcano agesinto dynamic maps showing a sequence of volcanic frontswhich identify movement (perhaps "apparent movement" tobe rationalised later by a proposal such as J. Wilson's (1963)"Hot Spot" theory). Similarly, conclusions reached by anumber of reputable geologists from different research anglesare treated as factual compilation material. This paper willhopefully clarify thinking, help assess models, and identifyfuture research areas.

WAITEMATA TECTONIC EVENT ANDSUBSEQUENT INTERVAL (26-15 Ma)

The Waitemata Tectonic Event (26-25 Ma) ended along period of relative tectonic stability. It created theunconformity between the Te Kuiti and Waitemata (originallyMahoenui) Groups (Henderson & Grange 1926), andtriggered the establishment of a new southwestwardssubduction system beneath Northland (Isaac et al. 1994;Brathwaite & Skinner 1997; Hayward et al. 2001). Thepresumed absence of a subduction trough at that early stageof the system's development provided the rare conditionsfor offshore sediments and ophiolites to be conveyed forwardon to a sinking Northland, creating the Northland Allochthon24-23 m.y. ago (Kear 1958, 1988; Ballance & Spörli 1979;Isaac et al. 1994; Rait 2000).

Volcanism began in "Greater Northland", which includesManukau Heads and northernmost Coromandel (Fig. 1), by23 m.y. ago. The time taken (2-3 m.y.) for the subductingslab to reach the "depth for volcanism" is broadly comparablewith an appropriate calculation for the Hikurangi systemtoday (3.5-5.5 m.y.). No volcano migration pattern has beenidentified from the many Greater Northland volcano ages(Smith et al. 1989; Hayward 1993; Hayward et al. 2001).

Volcanism was mostly andesitic, but included some acidicvolcanics (dacite) in the eastern Marshall Belt, and some

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362 New Zealand Journal of Geology and Geophysics, 2004, Vol. 47

• Northland Allochthon178°E

East Coast Allochthonlimit

Dotted coastal outline as at

pre-Kiwitahi Tectonic Event(c15Ma)

36°S -

Manukau HbWaitemata Hb

Tuakau-Merce

Ka

RAGLAN38°S Pirongia & Alexandra Volcanics

KAWHIA

40°S •

Dashed coastal outline as atpre-Kaimai Tectonic Event

(5-2.5 Ma)

100 200 kmi

176°E 178°E

Fig. 1 A "dynamic map" showingthe relationship of text localities tothe North Island tectonic/volcanicelements summarised in thispaper. Major transcurrent faultmovements, deduced by severalauthors from widely differentresearch angles, are seen ascompatible with movement alongthe inferred trace of the AlpineFault when it moved through bothislands. The East Coast was moved200 km south, between 15 and 5 Ma(from "dotted" to "dashed" coastaloutline). The 30° of rotationalopening of the Central VolcanicRegion (CVR) since 2.5 Ma movedthe northern East Coast a further100 km southeastwards (from"dashed" to "full" coastal outline),in three stages identified as theMangakino, Manawahe, andTaupoVolcanic Zones. Selected volcanoesshown in each of the volcanic zonesare: Mangakino V.Z.:1 Mangakino,2 Titiraupenga, 3 Pureora;Manawahe V. Z.: 1 Manawahe,2 Maungakatote, 3 Hauhungatahi;Taupo V. Z.: 1 White Island,2 Whale Island, 3 Mt Edgecumbe,4 Tarawera, 5 Maungakakaramea,6 Tauhara, 7 Pihanga, 8 Tongarirowith Ngauruhoe, 9 Ruapehu. Thesignificant bending of the AlpineFault trace resulted fromcurvature imposed on the NorthIsland since 15 Ma, determined bythree different authors as 60-70°(including the 30° for the CVR).

basic volcanics (basalt) in the western Searle Belt (Kear1994). The latter included offshore volcanoes which providedvolcanic material to the coastal area and to the Waitemata"inter-arc flysch basin" between the belts (Ballance 1974,1976b; Hatherton etal. 1979; Hayward 1979, 1993; Herzer1995; Raza et al. 1999; Hayward et al. 2001).

KIWITAHI TECTONIC EVENT AND SUBSEQUENTINTERVAL (15-5 Ma)

Development of activityThe Kiwitahi Tectonic Event (15-14 Ma) replaced theconsistently random volcanism in Greater Northland withvolcanism which migrated southeastwards to Kawhia and

Waihi from 14 to 5 m.y. ago. It remained in the two andesiticbelts, with the same contrast in the accompanying volcanism.No significant primary difference exists between Coromandeland Kiwitahi (Searle Belt) andesites. However, an importantsecondary difference was created in Coromandel, wheregeothermal activity, accompanying the later rhyoliticvolcanism (beginning 11-10 m.y. ago; Adams et al. 1994;Edbrooke 2001), hydrothermally altered considerablevolumes of pre-existing Coromandel andesites to propylite.Kiwitahi andesites, accompanied only by basalt (e.g., atTauhei, "with Pirongia affinities"; J. J. Reed in Kear &Schofield 1978), were never hydrothermally altered in acomparable way.

Waitemata Basin sedimentation ended with the KiwitahiEvent (15-14 Ma), and the two belts came closer together—

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Kear—Neogene tectonism & volcanism, North Island 363

the eastern Searle Belt (inland Kaipara Harbour) effectivelymoved east to the new Kiwitahi Volcanics alignment. Themany Coromandel and Kiwitahi ages (e.g., Skinner 1986;Black et al. 1992; Adams et al. 1994) show clearly thesubsequent apparent southeastward (later becomingsouthward) migration (Fig. 2). The orientation of thesubduction system (15-5 Ma) is discussed below.

There has been some past confusion regarding isochrons(Challis 1978; Brothers 1984,1986). Migration is best shown,not by connecting volcanoes of similar age, but as asuccession of volcanic fronts, each indicating the limit ofvolcanism at a stated time (Fig. 2). Thus, the 7 Ma front hasno older volcanism to its southeast, but volcanism of thatage could occur anywhere within reason to its northwest.

Volcanism continued offshore between Northland andTaranaki (King 1990; Bergman et al. 1992). King & Thrasher(1992) gave ages as 13-8 Ma in offshore Taranaki, whileHerzer (1995) noted that most ages were "between 16 and12 Ma", and that "there appears to be a southeastwarddecrease in volcano ages from Early to Late Miocene overthe short distance from the Manukau massif into the TaranakiBasin". Thus, western offshore volcanism was comparablein age and migration to that onshore.

From 15 to 5 Ma, some 25° of curvature (from a presumedoriginal Pacific rim alignment) was imposed on the NorthIsland (Kear 1963, fig. 101), estimated from the local trendsof the basement regional structural arc (Macpherson 1946),and of later volcanic alignments (Kear 1964). Ballance(1976a) estimated some 40° of rotation up to 3 m.y. ago.

Transcurrent movementCole (1986), Adams et al. (1994), and Kear (1997b) allattributed the above migration of volcanism to movementon a major transcurrent fault, which they all figured as joiningthe Alpine Fault in the South Island. The implication is thatthe North Island movement took place along the Alpine Faultwhen it was moving through both islands (H. W. Wellmanpers. comm. 1993). Both the subduction system and the EastCoast were moved southeastwards at that time (Fig. 3). TheNorth Island section has since been abandoned.

Evidence of such transcurrent movement (of c. 200-300 km) is widely accepted, but seldom seen as having asingle underlying cause or alignment. Its recognition iswidely based: Cole (1986) and Adams et al. (1994) onvolcanism; Mortimer (1995) on an early Cretaceoussedimentary basin; Leverenz & Ballance (2001) on lateMesozoic "Waioeka Petrofacies"; Watters (1986)on Northland-derived clasts in East Coast Ihungiaconglomerates; Kear (1957b) and Shane et al. (1998) onCoromandel pumice in East Coast Miocene sediments; andKear (1997b) on the East Coast Allochthon's movement fromoffshore Northland (Fig. 3)—a movement accepted as"possible" by Ballance (1999). The alignment adopted here,along the trace of the Alpine Fault (Fig. 3), is thought to becompatible with all those listed above in this paragraph.

The southward movement of the subduction system ledto a progressive spreading from the northwest of relativetectonic quiescence (Kear 1963,1994,1997b), shown today,anecdotally, by the rarity of local felt earthquakes north ofHamilton. That quiescence was accompanied by intraplate,predominantly basaltic, Kerikeri volcanism from c. 10 Ma(Smith et al. 1993). Successive volcanic fronts mark thesoutheastern limit of that intraplate volcanism for the stated

* = rhyolite t = basalt Tt = Tauhei (age unknown)

Fig. 2 Dynamic figure showing migration of Coromandel-Kiwitahi volcanism. Ages are given in Ma (principally from Skinner1986, Black et al. 1992, and Adams et al. 1994) alongside thetriangles which show volcanoes and volcanic centres within theMarshall (Coromandel) and Searle (Kiwitahi) Belts, separated bythe Volcanic Divide. The volcanic fronts (thick lines) indicate thesoutheast limit reached by the migration of volcanism by the dateshown (e.g., 7 Ma). No volcanism existed then to the southeast ofeach front, but volcanism of that age could have been locatedanywhere to its northwest. The base map has been adjusted to alocation prior to the formation of the Hauraki Graben, bringing theCoromandel and Kiwitahi volcanics much closer together.

time (Fig. 3). No vents existed to the southeast of any frontat the time indicated. However, vents could be activeanywhere to the northwest of that front, and so an apparentnorthward movement of centres took place from Raglan at2.5 Ma to Auckland today (Briggs et al. 1989).

KAIMAI TECTONIC EVENT AND SUBSEQUENTINTERVAL (5-0 Ma)

The Kaimai Tectonic Event (5-2.5 Ma) ended the simplesoutheastward migration of subduction-related volcanism.At Waihi (Brathwaite & Christie 1996), the establishedsequence of Coromandel volcanism (determined fromSkinner 1986, fig. 4, 5), of andesitic followed by rhyoliticvolcanism 0.5-2 m.y. later, was repeated. Subsequently,andesitic volcanic centres moved southwards from Te Puke(2.95 Ma; Stipp 1968), through Titiraupenga (1.9 Ma; Wilson

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364 New Zealand Journal of Geology and Geophysics, 2004, Vol. 47

15 Ma23-15 Ma

Extent ofAllochthonoffshore(Haywardetal. 2001)

\

14 Ma15.9-14 Ma

8 Ma9.9-8 Ma

6 Ma7.9-6 Ma

2 Ma2.9-2 Ma

1 Ma1.9-1 Ma

Fig. 3 (above and opposite) Alpine Fault in the North Island 15-0 Ma. The 200-300 km of displacement along the fault moved to thesoutheast (i.e., towards the East Coast region): (a) the subduction system and subduction-related volcanism; (b) the East Coast regionitself; (c) the "East Coast Allochthon" that had been part of the Northland Allochthon; (d) Miocene sediments containing pumice fromCoromandel; (e) a Cretaceous basin; (f) the late Mesozoic Waioeka petrofacies in part; and (g) Northland clasts in Ihungia conglomerates.The 60-70° of implied rotation is confirmed from volcanic and paleomagnetic studies. The movement of the subduction system and

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Kear—Neogene tectonism & volcanism, North Island 365

12 Ma13.9-12 Ma

10 Ma11.9-10 Ma

4 Ma5.9-4 Ma

3 Ma3.9-3 Ma

OMa0.9-0 Ma

Active Alpine Fault and branches

Abandoned trace of Alpine Fault

Time (Ma) for above

Subduction trough (full line relatedto volcanism; otherwise dashed)

Rotational rifting

Allochthon areas

Coromandel pumice deposits

Limit of "tectonic quiescence"

Subduction-related volcanism

0 200kmI i

Post-subduction volcanism

Time interval covered by above

3Ma

v V3.9 - 3 Ma

Alpine Fault caused a zone of relative "tectonic quiescence" to extend progressively southeastwards through Northland and SouthAuckland. Its location, as shown here, is that of the volcanic front of the accompanying post-subduction intraplate volcanism for thetimes shown.

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366 New Zealand Journal of Geology and Geophysics, 2004, Vol. 47

1986) and Puerora (1.6 Ma; Cole & Teoh 1975) to thepresently active Tongariro Centre, while the later rhyoliticcentres spread complexly, southwards from Waihi (2.6-1.5Ma; Brathwaite & Christie 1996) through Kaimai andMangakino (1.7-0.95 Ma; Pringle et al. 1992) to Maroa andTaupo (active from at least 330 ka; Wilson et al. 1986), andESE to Okataina (active from 400 to 390 ka; Nairn 1989,2002).

In the western coastal area, the Kaimai Tectonic Eventcaused the southeastward migration pattern to be locally andtemporarily reversed, from Kawhia (c. 5 Ma; Brothers 1986,fig. 9) to Raglan (Alexandra Volcanics 2.7-1.6 Ma; Briggsetal. 1989). Subsequently, it jumped southwards from Raglanto Taranaki (active since 1.7 Ma; Neall et al. 1986).

An additional 35–40° of curvature was imposed on theNorth Island during this period through the rotational riftingof the Hauraki Graben (opening by nearly 10°) and theCentral Volcanic Region (CVR, c. 30°). The Hauraki Grabendid not exist when rhyolitic rock from Coromandel wastransported across that area to be included in conglomeratesof Tuakau-Mercer less than 3 m.y. ago (Battey 1949). TheCVR (Grindley 1960; Thompson 1964; Thompson et al.1966) is a comparable structure of virtually identical age. Itsrotational rifting has amounted to c. 30° since the Pliocene(Kear 1963, fig. 101), and is implicit in King's (2000)reconstructions of North Island movement since 5 Ma.

Like the transcurrent movements described above, thisrotational movement is also widely acknowledged: Ballance(1976a) estimated 40° of rotation to 3 Ma, and 30° sincethen; Walcott & Mumme (1982) noted 60° of rotation since15 Ma on paleomagnetic grounds; Howell (1985), Stern(1986), and Scheibner et al. (1991) showed the CVR on mapsas the triangular termination of the Havre Trough riftingstructure, and implied that the CVR has opened rotationallyc. 30° as the latter structure has opened by normal rifting;King & Thrasher (1996) noted New Zealand's rotationrelative to the Western Platform; and Beanland & Haines(1998) used a detailed tectonic analysis to ascribe the rotationof the Hikurangi forearc to extension in the Taupo VolcanicZone (TVZ; Healy 1962, 1964) which terminates in centralNorth Island.

Rotational rifting has been the most important movementin the North Island since 2.5 Ma, with no evidence ofmovement on the Alpine Fault since then.

DISCUSSION

Development of the Central Volcanic Region (CVR)Features

An important feature of the CVR (Fig. 4) is its elongatedtriangular shape, open to the NNE, with near-straight longmargins. The straightness in the southeast, at the limit of allvolcanic vents, is widely accepted (e.g., by Healy 1962,1964;Thompson 1964; Cole 1986). That to the west is determinedby the limits of vents in volcanic highland localities,particularly Hauhungatahi and Pureora. This has beenaccepted by Stern (1986), Kear (1997a), and Beanland &Haines (1998), and provides a setting that is consistent witha rotational movement of c. 30°, in which the southeastmargin has essentially rotated away from the western margin.

Figure 4 shows the region as comprising threeprogressively younger volcanic zones, based on manypublished dates (listed in Kear 1994, fig. 2). "Zone" in this

sense combines the concepts of time and space. Each zoneis bounded in its southeast by a straight-line volcanic front(the limit then, of the migration of volcanism due to rotationalrifting). Each zone covers, in time, all the interval since theprevious zone. It covers, in space, all the area of activevolcanism during that time, that is, between its volcanic frontand that of the previous zone, plus other areas (shared withanother zone) of active volcanism within its time range.

All zones have had major rhyolitic centres centrally, andlarge andesitic volcanoes in their south. Three young, small,andesitic volcanoes (Whale Island, Mt Edgecumbe, Tauhara),with rocks that are chemically dacitic (Duncan 1970), arelocated on today's volcanic front. The comparable Manawahevolcano (425 ka; Broughton 1988) was apparently on thevolcanic front of its time, and was subsequently all but buriedby a Matahina Ignimbrite flow from Okataina (Fig. 5).Perhaps the comparable volcano Maungakakaramea(Rainbow Mt) similarly indicates the location of the steadilymoving volcanic front of its time (160 ka; I. A. Nairn inBrowne & Lloyd 1986).

The naming of these three zones, and the recognition oftheir progressive creation, provides an integrated explanationof: (1) the CVR as a dynamic and developing feature; (2) itsstraight-sided triangular shape; (3) its age being limited tothe last 2.5 m.y.; (4) the lack of volcanic vents older than400-350 ka southeast of the then volcanic front (similarlyfor the 950 ka front); (5) the broad northeast-alignedexpansion and sinking observed during the 1987 Edgecumbeearthquake, and the rifting during the 1886 Taraweraeruption; and (6) the compatibility with the simultaneousdextral rotation which imposed 30°+ of curvature on thesouthern North Island.

Mangakino Volcanic Zone

The Mangakino Volcanic Zone (new name) covers the timefrom the beginning of the CVR, probably 2.5 Ma (its oldestrocks are a little over 2 m.y. old), up to c. 950 ka. It is namedafter the Mangakino Basin, which lies west of the TaupoVolcanic Zone (Ewart & Healy 1966)—the MangakinoCentre or Caldera of Wilson (1986) and Krippner et al.(1998). It is the source of at least three well-erodedignimbrites which extend into the King Country, and of othersextending elsewhere, including southeastwards. The formerhave been dated (Pringle et al. 1992) as 1603-954 ka. Thezone includes the large eroded andesitic cones of Titiraupengaand Pureora (aged 1.9 and 1.6 Ma, respectively; Stipp 1968).

Manawahe Volcanic Zone

The Manawahe Volcanic Zone (new name) covers fromc. 950 ka until some time, not yet defined precisely, betweenc. 400 and 350 ka. It is named from the 425 ka andesitic-dacitic Manawahe volcano that marked the volcanic fronttowards the end of that time (Duncan 1970; Broughton 1988;Kear 1997a). Centrally, the products of significant rhyoliticvolcanism are poorly preserved due to deep burial (Wilsonet al. 1986). In the south, the zone includes the extinctandesitic volcanoes of Maungakatote and Hauhungatahi(500+ ka; Hackett 1985).

Taupo Volcanic Zone

The TVZ (e.g., Healy 1962, 1964; Cole 1979; Stern 1986)covers the latest interval from that same time (c. 400-350ka) to the present. Volcanic activity included: (1) the younger

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Kear—Neogene tectonism & volcanism, North Island 367

ICM

I I / t f

Maungakatote

Hauhangatahi

(A)

Subsidiaryparallel fault

" J u m P " t 0

line ofsubsidiary

parallel fault

i(.= greywackenow at

Otamarakau

Fig. 4 Dynamic diagram showing the evolution of the Central Volcanic Region, formed by rotational rifting, tearing along the abandonedtrace of the Alpine Fault, with the hinge point moving progressively southwards. It comprises three area/time zones, based primarily onages of volcanism: Mangakino Volcanic Zone from 2+ Ma to c. 950 ka (the names of its volcanoes and centres slope upwards on thisfigure); Manawahe Volcanic Zone from 950 ka to 400-350 ka (names horizontal); and Taupo Volcanic Zone from 400-350 ka to present(names slope downwards). Each zone has a straight "volcanic front" (limit then of southeastwards-extending volcanism)—at 950 ka,400-350 ka, and today. The northwestern limit may overlap with that of an earlier zone (much of the central Manawahe Zone wasdestroyed or buried by subsequent Taupo Zone activity). The insets A-D illustrate how blocks of Mesozoic greywacke (as at Otamarakau,asterisk here) might be left behind in the rotational rifting process: (A) shows initial rifting from the Alpine Fault during the MangakinoZone activity; (B) further similar rifting during part of the Manawahe Zone activity; (C) a jump to a new rifting line that had been asubsidiary fault, parallel to and east of the Alpine Fault; and (D) further rifting away from that fault line during the Taupo Zone activity.

parts of the andesitic Tongariro Volcanic Centre; (2) therhyolitic centres and geothermal activity of Taupo, Maroa,Reporoa, Rotorua, and Okataina; and (3) the andesitic-daciticvolcanism of Whale Island, Mt Edgecumbe, Tauhara, andMaungakakaramea.

Rate of opening ofWhakatane Graben and TVZ

The rotational rifting of the CVR is well illustrated by itsconstituent TVZ, and particularly by the northeastern partof the latter—the Whakatane Graben (Fig. 4, 5). After the1987 magnitude 6.3 Edgecumbe earthquake there (Beanlandet al. 1989; Nairn & Beanland 1989; Richardson 1989),Villamor & Berryman (2001) reported 2 m of vertical sinkingand 1.8 m of horizontal extension towards the southeast.Berryman & Beanland (1989) assessed the return period forM 6-6.5 earthquakes there as c. 100 yr. Slow sinking andsoutheastwards extension were accepted as being continuousbetween the larger movements during earthquakes, with

extension at the surface estimated at 7 mm/yr (e.g., Nairn &Beanland 1989).

Villamor & Berryman's photographs (2001) show thatthe extended surface collapsed through the ragged sinkingof weak blocks, aligned broadly parallel to the graben. Deepercross-sections (Browne & Lloyd 1986; Nairn 1989) showcompetent blocks descending along fault planes dipping at35-70°, perhaps during aftershocks. Thus, no voids wouldhave been created, and a greywacke basement would havebeen maintained throughout. Any surface depression wouldhave been filled rapidly with copious rhyolitic material(Pullar & Selby 1971; Kear 1997a).

If the above figures, determined after the 1987earthquake, were accepted as typical of a much longer period,a broad average rate of southeastwards surface extension ofthe Whakatane Graben (and of the TVZ and CVR) can beestimated as 1.8 cm/yr (1.8 m per 100 yr), plus 7 mm/yr(continuing), equalling a very broad 2.5 cm/yr, an estimatewhich requires confirmation.

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Fig. 5 Dynamic birds-eye sketch of Whakatane district (from Kear 1997a) showing: (a) the volcanic fronts of today and c. 400 ka,marked by small andesitic cones with dacitic affinities (Whale Island and Mt Edgecumbe, and Manawahe respectively); (b) the WhakataneGraben, which has rifted open between those fronts since c. 400 ka; (c) the Okataina Rhyolitic Centre and its major eruptive products—the Matahina Ignimbrite (c. 280 ka) and the Rotoiti Pumice Breccia (c. 50 ka); (d) the rift resulting from the eruption of Tarawera in1886, which caused extension in the same general NW-SE direction as that of the Whakatane Graben; (e) the epicentres of the Matata(1977 magnitude 5.4) and Edgecumbe (1987 magnitude 6.3) earthquakes—the latter causing up to 2 mof downwards displacement andup to 1.8 m of extension within the graben; (f) the Rangitaiki Plains which occupy the graben, and have been maintained above sea level(in spite of major downwarping) by the supply of alluvial pumiceous sediment from the Okataina Centre (including Tarawera) via theTarawera River, and from Taupo via the Rangitaiki River; and (g) the progressive movement of coastlines resulting from up to 10 km ofprogradation in the last 5000 yr (from Pullar & Selby 1971). The inclusion of the two volcanic front locations allows the reader toenvisage mentally both the steady continuous movement over 400 000 yr that extended the graben and plains at c. 2.5 cm/yr, and thebirth and development of the Okataina Centre.

Greywacke presence in CVR

The CVR's straight western limit is interpreted as aweakened major fault line from which the rotational riftingtook place, with the hinge point moving progressivelysouthwards (Fig. 4). Near Otamarakau (30–40 km west ofWhakatane), the presence of three surface greywacke"islands" surrounded by Rotoiti Breccia is explained bestby a jump from the 2+ Ma fault line to the line ofa subsidiary parallel fault to its east (Fig. 4A-D).Subsequently, much or all of the CVR's rifting would havetaken place along the complex western margin of theWhakatane Graben (Berryman et al. 1998), which containsthe epicentres (Fig. 5) of the 1977 Matata (Richardson 1989)and 1987 Edgecumbe (Smith & Oppenheimer 1989)earthquakes. The Whakatane Graben (and White IslandTrench; Fleming 1952) has opened nearly 10 km in the lastc. 400 ka (part confirmation of the above long-termextension rate of c. 2.5 cm/yr). Activity at Okataina, oneof the TVZ's two major rhyolitic centres, began 400-390ka ago (Nairn 1989, 2002).

This explanation, based on greywacke distribution, hasanother important implication. The commencement of theTVZ is otherwise identified by clusters of volcano ages from400-350 ka to today. Perhaps it was in fact triggered by amini-tectonic event, when the site of rifting jumpedsignificantly eastwards, an event which may be dated a littlemore precisely as c. 400 ka.

Orientation of subduction systems

Regarding the orientation of the Coromandel subductionsystem (15-5 Ma), Hatherton (1969) figured the Benioff zoneas deepening westwards, and suggested depths to it of110-140 km for Northland and c. 120 km for Hauraki-Coromandel—effectively 100-120 km for the Marshall Beltand 120-140 km for the Searle Belt. Brothers (1986, fig. 8)agreed with the former while suggesting that the latter mightreach 160 km in Northland. He accepted a deeper magmasource for his Tokatoka-Egmont West Belt than for hisWhangarei-Taupo East Belt—from which southwestwardCoromandel subduction could be inferred. However, Brothers

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also believed that northwestward Hikurangi subduction,oriented similarly to that today, was responsible forCoromandel volcanism. That conflict posed a problem,unresolved until now.

Spörli (1989) presented the options: whether thesubsequent directional change from Coromandel to Taupowas gradual or abrupt; and "whether it occurred by a swingfrom the NW trend of the Northland to the NE trend of theTaupo Volcanic Zone (Ballance et al. 1985) or whether thearcs were always northeast-trending and migrated to thesoutheast by the arc regression postulated by Brothers (1984)and Kamp (1984)". Since then, Spörli (1989) and Kear (1994,1997b) have favoured the former, which appears consistentwith King's (2000) reconstructions, while Herzer (1995) andBallance (1999) favoured the latter. Brathwaite & Skinner(1997) considered that, up to 14 Ma, the southwesterlysubduction beneath Northland continued for Coromandel(with part in the north becoming extinct), but thatsubsequently northwestward Hikurangi subduction replacedit. Herzer (1995) illustrated "mid-late Miocene subduction"towards the northwest, affecting the Colville Ridge and allof the North Island south of Greater Northland, includingCoromandel. This followed a sudden swing in thedirection of subduction of some 75°—Ballance's (1999)"reorganization" at 15 Ma.

Volcanic activity certainly moved progressively trench-wards in Coromandel, but at right angles to Brothers'direction of "regression". Rhyolitic volcanism (Fig. 2,asterisks) at any one place was always younger than andesitic,and generally farther east (Skinner 1986, fig. 4, 5). Thus,younger rhyolitic volcanism replaced older andesiticvolcanism in new eastern areas of land created by that activity.Meantime, andesitic volcanism migrated farther southwards.Hence, "subduction regression" might be inferred towards atrench offshore from Coromandel.

Many points favour the acceptance of southwestward(becoming west-southwestward) subduction duringCoromandel volcanism (not west-northwestward"Hikurangi" subduction):1. A simple, continuous, and comparable apparent

movement of volcanism existed throughout the Neogene,from Northland to CVR (Fig. 3). King (2000) has alreadyfigured the steady movement of such a single subductionsystem from 27 Ma to today.

2. Dextral curvature was imposed on the North Islandcontinuously—slower during Coromandel volcanism andfaster during CVR volcanism, but otherwise closelysimilar throughout.

3. Contemporary volcanism in Northland, Coromandel, andCVR was everywhere relatively constant across the strikeof a single (but progressively migrating) subductionsystem, while any major changes occurred down-dip—the direction in which the depth to the Benioff zoneincreased (e.g., the accompanying rhyolitic volcanismwas always shallower than basaltic).

4. The down-dip sequence in the west-southwestwardsubduction system of Coromandel is virtually identicalto that in the northwestward (Hikurangi) subduction ofthe CVR. The most complete sections show: (a) trenchor trough; (b) coastline; (c) rhyolitic volcanism (easternCoromandel and Taupo-Okataina) followed to the westby older andesitic volcanism (western Coromandel andTitiraupenga-Pureora), both of the Marshall Belt; (d)volcanic divide between the belts (Kear 1997a,b); and

(e) andesitic and basaltic volcanism of the Searle Belt(Kiwitahi and Alexandra Volcanics and offshore). Theclose similarity of these sequences was maintained after2.5 Ma, in spite of 40° of rotation being imposed.

5. The "subduction regression" noted above for Coromandelis mirrored closely in the CVR. Pureora-Titiraupengaandesitic volcanism of 1.9-1.6 Ma was presumably closeto the volcanic front of that day, as Ruapehu andNgauruhoe are today. Since then, the front has extendedsoutheastwards (subduction regression) and the newlycreated area has become the site of the subsequentrhyolitic volcanism that continues today. At the same time,major andesitic volcanism has migrated southwards tothe Tongariro Centre.Recognition of the configuration of the subduction system

for Coromandel, and of the fundamental difference betweenthe Marshall and Searle Belts, provides vital information forany study of New Zealand's Neogene volcanic processes.The "Volcanic Divide" (Kear 1997a,b) between those twobelts is located where the Benioff zone is c. 120 km deep.There, the volcanism accompanying the major andesiticactivity changes abruptly and completely from acidic(rhyolite-dacite) to basic (basalt). Farther west, Hatherton(1969), Brothers (1984,1986), and Stern (1986) reported K-rich volcanics at greater depths (over 200 km). Whether thisidentifies an important deeper part of the Searle Belt, orwhether it relates to magma generation within a differentwestern terrane, is a subject for future research.

Alpine Fault in the North IslandLocation

The Alpine Fault terminates today at the Wairau Fault, butmany authors have opted to show some of its c. 450 km ofmovement as continuing into the North Island along knownor presumed transcurrent faults (e.g., Fleming 1969; Suggateetal. 1978; Stevens 1980; Cole 1986; Ballance 1993; Adamset al. 1994; Stirling at al. 1998).

The general location for the fault's 200-300 km ofmovement in the North Island must have been closelyoffshore from Coromandel (west of Miocene pumiceoussedimentation; Kear 1957b; Shane et al. 1998), turningsharply southward at the Bay of Plenty coastline, andcontinuing south, inland of the East Coast region. Thedetailed alignment proposed here (Fig. 3,4) follows the routeof the CVR's western margin where the straightness and easeof rifting imply a major fault trace. Southward extrapolationof that line (via the North Island coast near Wanganui andthe western margin of the Marlborough schist), heads forthe point where the Wairau Fault branches from the maintrend of the Alpine Fault.

Leverenz & Ballance (2001) published another detailedlocation for a major North Island strike-slip Wellington-Mohaka-Whakatane Fault. They considered that it moved 98-85 Ma. However, some Alpine Fault movement in the NorthIsland involved Neogene rocks, and the Wellington andWhakatane Faults seem topographically much younger thanMesozoic. That conforms with Beanland & Haines' (1998)view of the youthfulness of both the CVR and their NorthIsland Dextral Fault Belt (NIDFB)—to which both theWellington and Whakatane Faults belong. It is relevant thatalthough the Whakatane Fault is now 100 km away from theadopted location of the Alpine Fault (Fig. 3), it would havebeen very much less than that before the opening of the CVR.

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The merits of the Fig. 3 location are:(1) The CVR's straight western boundary is recognised as a

line of weakness of a major fault, along which the CVRreadily opened.

(2) The NIDFB's unity is retained; the eastern route separatestwo of its constituent faults (Whakatane and Waiohau),which are < 10 km apart.

(3) The extrapolation of the Alpine Fault's North Island traceheads directly for its main South Island trend, not forone of its branches.

(4) The extrapolation west of the Marlborough schist leavesall South Island younger schist (White 2002) and allonshore North Island schist, including lava inclusions(Graham 1987) andParikino cores (McLernon 1976), onthe same eastern side of the combined fault.

(5) The combined faultline is smoothly curved through bothislands. It reflects c. 60-70° of rotation, since the KiwitahiEvent, of an elongated, initially near-straight, strike-slipfault traversing both islands of New Zealand, making ithighly curved (Fig. 1). Its one sharp bend, near the Bayof Plenty coast, exists where the effect would have beengreatest of the 40° of rotational rifting since 2.5 Ma.

Timing

The tectonism that caused the movement on the Alpine Faultis accepted here as the cause of the southward migration ofCoromandel and Kiwitahi volcanism. Before 15 Ma, GreaterNorthland volcanism showed no such migration trends. Thus,major Alpine Fault movement in the northern North Islandis accepted as beginning c. 15 Ma.

Alpine Fault termination - South Island comparisons

The southward migration of the zone of tectonic quiescenceand of intraplate volcanism since 10 Ma is consistent withthe progressive extinction of the northernmost parts of theAlpine Fault (Brathwaite & Skinner 1997; Kear 1997b). Theconfiguration at the fault's termination in the north couldhave been similar to that today in the South Island, wherethe Wairau Fault curves eastwards (as shown in Fig. 3'sindividual maps up to 6 Ma, and possibly up to 3 Ma).

No certain Alpine Fault movement is known in the NorthIsland since the Kaimai Event began (5 Ma). By then, theAlpine Fault would have become inactive north of the Bayof Plenty, through progressive "extinctions". Subsequently,however, the termination must have moved from the Bay ofPlenty to Cook Strait in one or more jumps. If there hadbeen more than one, the configuration in the northern SouthIsland of three faults (Wairau, Awatere, and Hope) branchingto the east, may indicate that comparable faults existed inthe North Island during this jumping process. Two localitiesseem possible (dashed lines on Fig. 3): Manawatu andKaimanawa. The former is suggested by the existence of theManawatu Gorge (which cuts through the North Island's mainrange there), where the local rocks are highly brecciated.The Kaimanawa Fault was mapped by Grindley (1960)around a basement high represented by the KaimanawaMountains. However, the question remains as to whetherthese two faults in the North Island did act in this way.

Comparable fault patterns in the westThe North Island's Alpine Fault System is interpreted as amajor north-trending transcurrent fault with subsidiary faultsbranching eastwards from it, each of which acted as the

northern termination of the main fault for a time (Fig. 3).Subsequently, and progressively, each branch fault becameextinct, along with that part of the main fault down to thenext branch fault.

Detailed mapping in the Waikato Coalfields (Kear &Schofield 1978), with good mining and drillhole control,showed a similar structural pattern well west of the AlpineFault, that is, a major set of presumed transcurrent faultstrending broadly north from which subsidiary faults(eventually normal) branched off eastwards (Kear 1997b).In the Drury-Hunua-Franklin region, south of Auckland City,more than one set of the major north-trending faults is present,which led to the concept of "block-faulting" (e.g., Bartrum& Branch 1936; Schofield 1958; Kear 1959). There, and atKaawa (Kear 1957a), the fault planes subsequently becameconduits for intraplate basalt volcanoes after tectonicquiescence (and tension) arrived from the north. This faultingpattern was imposed after the Kiwitahi Tectonic Event (i.e.,post-15 Ma) during the period when major curvature wasbeing imposed on the North Island.

The North Island Dextral Fault BeltThe rifting of the CVR would have affected northern areasfirst with progressively more southern parts becomingaffected as the hinge point moved southwards. The circularrotation would have imposed stress on north-south tractsprogressively farther east by effectively increasing theirlengths. The resulting strain could have been relieved bydextral transcurrent faulting—within the North Island DextralFault Belt (Beanland 1995). This simple interpretationimplies that that belt was probably initiated by the KaimaiTectonic Event, and has probably existed for little more than2.5 m.y. Beanland & Haines (1998) reached a similarconclusion after far more thorough research.

Today, the belt is most active in the south, shown initiallyby the increasing presence southwards of faults mapped asactive (Grindley 1960; Kingma 1962,1967; Healyetal. 1964),and later by the detailed work of Beanland & Haines (1998),and Reyners (1998). However, faults in the north (e.g.,Whakatane; Grindley 1960; Healy et al. 1964) are located instraight-aligned river valleys, typically many tens of kilometreslong and a hundred or more metres wide, implying a widezone of brecciation. It is therefore concluded that these faultswere once as active as, for example, the Wellington Fault istoday. Presumably, as the hinge point of rotation movedsouthwards, the greatest activity tended to move southwardswith it, decreasing in the north at the same time.

CONCLUSIONS

1. The pattern of North Island tectonism is shown to be oneof dynamic, continuing, and (above all) interpretabledevelopment and change. It has always been closelyconnected to that in the South Island, through the AlpineFault, originally common to both islands.

2. The Waitemata Tectonic Event (26-25 Ma) endedthe previous tectonic stability, and initiated a newsouthwestward subduction system which created theNorthland Allochthon (24-23 Ma) and subsequentlyGreater Northland volcanism (23-15 Ma).

3. The Kiwitahi Tectonic Event (15-14 Ma) ended bothWaitemata Basin sedimentation and Greater Northland

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volcanism, substituting subduction-related volcanismwhich migrated southwards (up to 5 m.y. ago) throughCoromandel, the Kiwitahi Volcanics, and the westerncoastal and offshore areas. That migration was associatedwith 200-300 km of dextral transcurrent movement alongthe Alpine Fault, and the following were also movedprogressively southwards (Fig. 3): the subduction system,the East Coast, and other well-documented features—aCretaceous sedimentary basin and Waioeka petrofacies(Mortimer 1995; Leverenz & Ballance 2001); Ihungiaconglomerates (Watters 1986); Miocene pumiceoussediments (Kear 1957b; Shane et al. 1998); and the EastCoast Allochthon (Kear 1997b). Segments of the AlpineFault seem to have become progressively inactive fromthe north, probably together with a sequence of east-trending branch faults, comparable with the Wairau,Awatere, and Hope Faults of the South Island today. InSouth Auckland and Waikato, a similar faultingconfiguration exists, of major north-trending transcurrentfaults with minor (eventually normal) faults branchingoff to the northeast.

4. The southward migration of the subduction system,through transcurrent faulting, led to the progressivesouthward spreading of relative tectonic quiescencethrough Northland and South Auckland, and ofaccompanying intraplate Kerikeri volcanism from 10 Ma.

5. The Kaimai Tectonic Event (5-2.5 Ma) temporarilyhalted, or even reversed, the southward migration ofvolcanism. It also caused, from c. 2.5 Ma, progressiverotation due to the rifting open of the Hauraki Grabenand the CVR, adding 40° of curvature to the 25° alreadyimposed on the North Island since 15 Ma. Such rotationis consistent with the North Island tectonic, volcanic,paleomagnetic, and geophysical studies recorded above,and with the Circum-Pacific "Tectonic" (Scheibner et al.1991) and "Tectonostratigraphic Terrane" (Howell 1985)published maps. It probably triggered the development,since 2.5 Ma, of the North Island Dextral Fault Belt. Itinitiated major CVR volcanism in which three zonesdeveloped progressively—Mangakino (2+ Ma to 950 ka),Manawahe (950 to 400-350 ka), and Taupo (400-350 kato present day). Each shows: (a) a straight-line volcanicfront for that time marked by smaller andesitic volcanoeswith dacitic affinities; (b) major rhyolitic volcanic centresand peripheral geothermal activity, in central areas; and(c) major andesitic volcanoes in the south.

6. Tectonic and volcanic development through the Neogenehas been continuous. There have been significant changesat each tectonic event, but the basic pattern has remained.The direction of subduction has rotated dextrally, at firstslowly and then faster, from southwestward (Northland),through west-southwestward (Coromandel), to becomewest- northwestward (Hikurangi) as its influencemigrated progressively southwards.

7. The constancy of the overall pattern is well illustrated bythe recognition of the Marshall and Searle Beltsthroughout the Neogene, with their contrasting acidic andbasic volcanic accompaniments to their andesiticvolcanism. The abrupt and complete change from one tothe other at the volcanic divide, where the descending

Benioff zone is c. 120 km deep, will be one importantfactor in eventually understanding the basic mechanismof North Island Neogene volcanism. Another will be asecond contrast between the two belts, in that, in theMarshall Belt, andesitic (earlier) and rhyolitic (later)volcanism have occupied adjacent localities at differenttimes while, in the Searle Belt, andesitic and basaltic rocksare far more closely associated and can be erupted fromthe same vent (as at Karioi volcano, 2.9-2.3 Ma; Briggset al. 1989, cf. Samoa; Kear & Wood 1959).

ACKNOWLEDGMENTS

My grateful thanks remain to the many individuals (in Kear 1994)whose discussions helped develop the ideas here. More recently,my sincere thanks are due to Peter Ballance, Bruce Hayward, IanNairn, and Bruce Thompson, for their valuable comments on thismanuscript, and to Bernhard Spörli and Tim Stern for theirthoughtful and highly beneficial refereeing.

REFERENCES

Adams, C. J.; Graham, I. J.; Seward, S.; Skinner, D. N. B. 1994:Geochronological and geochemical evolution of lateCenozoic volcanism in the Coromandel Peninsula, NewZealand. New Zealand Journal of Geology and Geophysics37: 359-378.

Ballance, P. F. 1974: An inter-arc flysch basin in northern NewZealand: Waitemata Group (upper Oligocene to lowerMiocene). Journal of Geology 82: 439–471.

Ballance, P. F. 1976a: Evolution of the upper Cenozoic magmaticarc and plate boundary in northern New Zealand. Earthand Planetary Science Letters 28: 356-370.

Ballance, P. F. 1976b: Stratigraphy and bibliography of theWaitemata Group of Auckland, New Zealand. New ZealandJournal of Geology and Geophysics 19: 897-932.

Ballance, P. F. 1993: The Paleo-Pacific, post-subduction, passivemargin thermal relaxation sequence (Late Cretaceous-Paleogene) of the drifting New Zealand continent. In:Ballance, P. F. ed. South Pacific sedimentary basins.Sedimentary basins of the world 2. Amsterdam, ElsevierScience. Pp. 93-110.

Ballance, P. F. 1999: Simplification of the Southwest PacificNeogene arcs: inherited complexity and control by aretreating pole of rotation. In: Mac Niocaill, C.; Ryan, P.D. ed. Continental tectonics. Geological Society of LondonSpecial Publications 164: 7-19.

Ballance, P. F.; Spörli, K. B. 1979: Northland Allochthon. Journalof the Royal Society of New Zealand 9: 259-275.

Ballance, P. F.; Hayward, B. W.; Brook, F. J. 1985: Matters arising:subduction regression of volcanism in New Zealand. Nature313: 820.

Bartrum, J. A.; Branch, W. J. 1936: Geology of Bombay-HappyValley area, Franklin County, Auckland. Transactions ofthe Royal Society of New Zealand 65: 386–404.

Battey, M. H. 1949: The geology of the Tuakau-Mercer area,Auckland. Transactions of the Royal Society of NewZealand 77: 429–455.

Beanland, S. 1995: The North Island dextral fault belt, Hikurangisubduction margin, New Zealand. Unpublished PhD thesis,lodged in the Library, Victoria University of Wellington,Wellington, New Zealand.

Beanland, S.; Haines, J. 1998: The kinematics of active deformationin North Island, New Zealand, determined from geologicalstrain rates. New Zealand Journal of Geology andGeophysics 41: 311-323.

Dow

nloa

ded

by [

Uni

vers

ity o

f In

carn

ate

Wor

d] a

t 06:

34 3

0 O

ctob

er 2

014

372 New Zealand Journal of Geology and Geophysics, 2004, Vol. 47

Beanland, S.; Berryman, K. R.; Blick, G. H. 1989: Geological in-vestigations of the 1987 Edgecumbe earthquake, New Zea-land. New Zealand Journal of Geology and Geophysics 32:73-91.

Bergman, S. C.; Talbot, J. P.; Thompson, P. R. 1992: The KoraMiocene submarine andesite stratovolcano hydrocarbonreservoir, northern Taranaki basin, New Zealand.Proceedings of the 1991 New Zealand Oil ExplorationConference. Wellington, Energy and Resources Division,Ministry of Commerce. Pp. 178-206.

Berryman, K.; Beanland, S. 1989: Evaluation of seismic hazard inthe Rangitaiki Plains, New Zealand. New Zealand Journalof Geology and Geophysics 32: 185-190.

Berryman, K.; Beanland, S.; Wesnousky, S. 1998: Paleoseismicityof the Rotoitipakau Fault Zone, a complex normal fault inthe Taupo Volcanic Zone, New Zealand. New ZealandJournal of Geology and Geophysics 41: 449–465.

Black, P. M.; Briggs, R. M.; Itaya, T.; Dewes, E. R.; Dunbar, H.M.; Kawasaki, K.; Kuschel, E.; Smith, I. E. M. 1992: K-Arage data and geochemistry of the Kiwitahi Volcanics,western Hauraki Rift, North Island, New Zealand. NewZealand Journal of Geology and Geophysics 35: 403–413.

Brathwaite, R. L.; Christie, A. B. 1996: Geology of the Waihi area,scale 1:50 000. Institute of Geological & Nuclear SciencesGeological Map 21, part sheets T13 and U13.1 sheet + 64p. Lower Hutt, New Zealand, Institute of Geological &Nuclear Sciences Limited.

Brathwaite, R. L.; Skinner, D. N. B. 1997: The Coromandelepithermal gold-silver province: a result of the collision ofthe Northland and Colville Volcanic Arcs in northern NewZealand. 1997 New Zealand Minerals and MiningConference Proceedings. Wellington, New ZealandMinistry of Commerce. Pp. 111-117.

Briggs, R. M.; Itaya, T.; Lowe, D. J.; Keane, A. J. 1989: Ages ofthe Pliocene-Pleistocene Alexandra and NgatuturaVolcanics, western North Island, New Zealand, and somegeological implications. New Zealand Journal of Geologyand Geophysics 32: 417–427.

Brothers, R. N. 1984: Subduction regression and oceanwardmigration of volcanism, North Island, New Zealand. Nature309: 698-700.

Brothers, R. N. 1986: Upper Tertiary and Quaternary volcanismand subduction zone regression, North Island, NewZealand. Journal of the Royal Society of New Zealand 16:275-298.

Broughton, A. K. 1988: Volcanology and petrology of theManawahe Volcano, Taupo Volcanic Zone. GeologicalSociety of New Zealand Miscellaneous Publication 41a:44.

Browne, P. R. L.; Lloyd, E. F. 1986: Water dominated geothermalsystems and associated mineralisation. New ZealandGeological Survey Record 11: 145-212.

Challis, G. A. 1978: Volcanism and volcanic trends in the geologicalhistory of New Zealand. In: Suggate, R. P.; Stevens, G. R.;Te Punga, M. T. ed. 1978: The geology of New Zealand.Wellington, Government Printer. Pp. 664-667.

Cole, J. W. 1979: Structure, petrology and genesis of Cenozoicvolcanism, Taupo Volcanic Zone, New Zealand—a review.New Zealand Journal of Geology and Geophysics 22: 631-657.

Cole, J. W. 1986: Distribution and tectonic setting of late Cenozoicvolcanism in New Zealand. Royal Society of New ZealandBulletin 23: 7-20.

Cole, J. W.; Teoh, L. H. 1975: Petrography, mineralogy, andchemistry of Pureora andesitic volcano, North Island, NewZealand. New Zealand Journal of Geology and Geophysics18: 259-272.

Duncan, A. R. 1970: Petrology and petrochemistry of andesite anddacite volcanoes in the eastern Bay of Plenty, New Zealand.Unpublished MSc thesis, lodged in the Library, VictoriaUniversity of Wellington, Wellington, New Zealand.

Edbrooke, S. W. comp. 2001: Geology of the Auckland area.Institute of Geological & Nuclear Sciences 1:250 000Geological Map 3. 1 sheet + 74 p. Lower Hutt, NewZealand, Institute of Geological & Nuclear SciencesLimited.

Ewart, A.; Healy, J. 1966: Mangakino geology. In: Thompson, B.N.; Kermode, L. O.; Ewart, A. ed. 1966: New Zealandvolcanology—Central Volcanic Region. New ZealandDepartment of Scientific and Industrial ResearchInformation Series 50: 48-60.

Fleming, C. A. 1952: White Island Trench—a submarine canyon.Proceedings of the 7th Pacific Science Congress III. Pp.210-212.

Fleming, C. A. 1969: The Mesozoic of New Zealand: chapters inthe history of the Circum-Pacific Mobile Belt. QuarterlyJournal of the Geological Society of London 125: 125-170.

Graham, I. J. 1987: Petrography and origin of metasedimentaryxenoliths in lavas from Tongariro Volcanic Centre. NewZealand Journal of Geology and Geophysics 30: 139-157.

Grindley, G. W. 1960: Sheet 8—Taupo. Geological map of NewZealand 1:250 000. Wellington, New Zealand, Departmentof Scientific and Industrial Research.

Hackett, W. R. 1985: Geology and petrology of Ruapehu volcanoand related vents. Unpublished MSc thesis, lodged in theLibrary, Victoria University of Wellington, Wellington, NewZealand.

Hatherton, T. 1969: The geophysical significance of calc-alkalineandesites in New Zealand. New Zealand Journal of Geologyand Geophysics 12: 436–459.

Hatherton, T.; Davey, F. J.; Hunt, T. M. 1979: Geophysicalanomalies and igneous bodies off the West Coast, NorthIsland. Journal of the Royal Society of New Zealand 9:13-28.

Hayward, B. W. 1979: Eruptive history of the early to mid MioceneWaitakere Volcanic Arc, and paleogeography of theWaitemata Basin, northern New Zealand. Journal of theRoyal Society of New Zealand 9: 297-320.

Hayward, B. W. 1993: The tempestuous 10 million year life of adouble arc and intra-arc basin—New Zealand's NorthlandBasin in the early Miocene. In: Ballance, P. F. ed. SouthPacific sedimentary basins. Sedimentary basins of theWorld, 2. Amsterdam, Elsevier. Pp. 113-142.

Hayward, B. W.; Black, P. M.; Smith, I. E. M.; Ballance, P. F.;Itaya, T.; Doi, M.; Takagi, M.; Bergman, S.; Adams, C. J.;Herzer, R. H.; Robertson, D. J. 2001: K-Ar ages of earlyMiocene arc-type volcanoes in northern New Zealand. NewZealand Journal of Geology and Geophysics 44: 285-311.

Healy, J. 1962: Structure and volcanism in the Taupo Volcanic Zone,New Zealand. In: Crust of the Pacific Basin. AmericanGeophysical Union Geophysical Monograph 6: 151-157.

Healy, J. 1964: Volcanic mechanisms in the Taupo Volcanic Zone.New Zealand Journal of Geology and Geophysics 7: 6-23.

Healy, J.; Schofield, J. C.; Thompson, B. N. 1964: Sheet 5—Rotorua. Geological map of New Zealand 1:250 000.Wellington, New Zealand, Department of Scientific andIndustrial Research.

Henderson, J.; Grange, L. I. 1926: Geology of Huntly-KawhiaSubdivision, Pirongia and Hauraki Divisions. New ZealandGeological Survey Bulletin n.s. 28. 127 p.

Herzer, R. H. 1995: Seismic stratigraphy of a buried volcanic arc,Northland, New Zealand and implications for Neogenesubduction. Marine and Petroleum Geology 12: 511-531.

Dow

nloa

ded

by [

Uni

vers

ity o

f In

carn

ate

Wor

d] a

t 06:

34 3

0 O

ctob

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014

Kear—Neogene tectonism & volcanism, North Island 373

Howell, D. G. ed. 1985: Tectonostratigraphic terranes of theCircum-Pacific region. Houston, Texas, Circum-PacificCouncil for Energy and Mineral Resources. Earth ScienceSeries 1. 581 p.

Isaac, M. J.; Brook, F. J.; Hayward, B. W.; Herzer, R. H. 1994:Emplacement of the Northland Allochthon. Institute ofGeological & Nuclear Sciences Science Report 92/24: 7-11.

Kamp, P. J. J. 1984: Neogene and Quaternary extent and geometryof the subducted Pacific Plate beneath North Island,New Zealand: implications for Kaikoura tectonics.Tectonophysics 108: 241-266.

Kear, D. 1957a: Stratigraphy of the Kaawa-Ohuka coastal area,West Auckland. New Zealand Journal of Science andTechnology B38: 826-842.

Kear, D. 1957b: Pumice chronology in New Zealand. New ZealandJournal of Science and Technology B38: 862-870.

Kear, D. 1958: Northland stratigraphy in the light of the Kaitaiaoil hole. New Zealand Geological Survey Conference 1958,Reefton, Abstracts. 1 p.

Kear, D. 1959: Drury coalfield, Auckland. New Zealand Journalof Geology and Geophysics 2: 846-869.

Kear, D. 1963: Geology of the Te Akau District, West Auckland,New Zealand, and its regional implications. UnpublishedPhD thesis, lodged in the Library, University of London,London, England (2 vol.). 599 p. (Copy lodged in Instituteof Geological & Nuclear Sciences Library, Lower Hutt,New Zealand.)

Kear, D. 1964: Volcanic alignments north and west of NewZealand's Central Volcanic Region. New Zealand Journalof Geology and Geophysics 7: 24-44.

Kear, D. 1988: Early Northland allochthonism. Geological Societyof New Zealand Newsletter 80: 27-33.

Kear, D. 1994: A "least complex" dynamic model for late Cenozoicvolcanism in the North Island, New Zealand. New ZealandJournal of Geology and Geophysics 37: 223-236.

Kear, D. 1997a: Whakatane's geological history. Whakatane, NewZealand, David Kear. 28 p. Reprinted in Historical Revue[Bay of Plenty Journal of History] 48, May 2000: 25-58.

Kear, D. 1997b: Volcanics and mineral deposits along a plateboundary. 1997 New Zealand Minerals and MiningConference Proceedings. Wellington, New ZealandMinistry of Commerce. Pp. 85-96.

Kear, D.; Schofield, J. C. 1978: Geology of the NgaruawahiaSubdivision. New Zealand Geological Survey Bulletin 88.168 p.

Kear, D.; Wood, B. L. 1959: The geology and hydrology of WesternSamoa. New Zealand Geological Survey Bulletin 63. 90 p.

King, P. R. 1990: Polyphase evolution of the Taranaki Basin, NewZealand: changes in sedimentary and structural style.Proceedings of the 1989 New Zealand Oil ExplorationConference. Wellington, Energy and Resources Division,Ministry of Commerce. Pp. 134-150.

King, P. R. 2000: Tectonic reconstructions of New Zealand. NewZealand Journal of Geology and Geophysics 43: 611-638.

King, P. R.; Thrasher, G. P. 1992: Post-Eocene development of theTaranaki Basin, New Zealand—convergent overprint of apassive margin. American Association of PetroleumGeologists Memoir 53: 93-118.

King, P. R.; Thrasher, G. P. 1996: Cretaceous-Cenozoic geologyand petroleum systems of the Taranaki Basin, New Zealand.Institute of Geological & Nuclear Sciences Monograph 13.

Kingma, J. T. 1962: Sheet 11—Dannevirke. Geological map ofNew Zealand 1:250 000. Wellington, New Zealand,Department of Scientific and Industrial Research.

Kingma, J. T. 1967: Sheet 12—Wellington. Geological map of NewZealand. 1:250 000. Wellington, New Zealand, Departmentof Scientific and Industrial Research.

Krippner, S. J. P.; Briggs, R. M.; Wilson, C. J. N.; Cole, J. W.1998: Petrography and geochemistry of lithic fragments inignimbrites from the Mangakino Volcanic Centre:implications for the composition of the subvolcanic crustin western Taupo Volcanic Zone, New Zealand. NewZealand Journal of Geology and Geophysics 41: 187-199.

Leverenz, A.; Ballance, P. F. 2001: Terrane affiliation andterrane boundaries of Mesozoic accretionary complexes,northeastern North Island: some implications from recycledclastics. New Zealand Journal of Geology and Geophysics44: 589-599.

McLernon, C. R. 1976: Oil prospecting wells 1971-1973 withadditions to "Oil Prospecting Wells 1865-1970". In: Beatus,S. N.; Francis, D. A. ed. Industrial Minerals and Rocks 7.Wellington, Department of Scientific and IndustrialResearch. 63 p.

Macpherson, E. O. 1946: An outline of Late Cretaceous and Tertiarydiastrophism in New Zealand. New Zealand Departmentof Scientific and Industrial Research Geological Memoir6. 46 p.

Mortimer, N. 1995: Origin of the Torlesse Terrane and coeval rocks,North Island, New Zealand. International Geological Revue36: 891-910.

Nairn, I. A. 1989: Sheet V16AC—Mount Tarawera. Geologicalmap of New Zealand 1:50 000. 1 map and notes.Wellington, New Zealand. Department of Scientific andIndustrial Research. 55 p.

Nairn, I. A. 2002: Geology of the Okataina Volcanic Centre. Instituteof Geological & Nuclear Sciences Geological Map 25. Scale1:50 000. 1 sheet. Lower Hutt, New Zealand, Institute ofGeological & Nuclear Sciences Limited. 156 p.

Nairn, I. A.; Beanland, S. 1989: Geological setting of the 1987Edgecumbe earthquake, New Zealand. New ZealandJournal of Geology and Geophysics 32: 1-13.

Neall, V. E.; Stewart, R. B.; Smith, I. E. M. 1986: History andpetrology of the Taranaki volcanoes. Royal Society of NewZealand Bulletin 23: 251-263.

Pringle, M. S. McWilliams, M.; Houghton, B. F.; Lanphere, M.A.; Wilson, C. J. N. 1992: 40Ar/39Ar dating of Quaternaryfeldspar: examples from the Taupo Volcanic Zone, NewZealand. Geology 20: 531-534.

Pullar, W. A.; Selby, M. J. 1971: Coastal progradation of RangitaikiPlains, New Zealand. New Zealand Journal of Science 14:419–434.

Rait, G. J. 2000: Thrust transport directions in the NorthlandAllochthon, New Zealand. New Zealand Journal of Geologyand Geophysics 43: 271-288.

Raza, A.; Brown, R. W.; Ballance, P. F.; Hill, K. C.; Kamp, P. J. J.1999: Thermal history of the early Miocene WaitemataBasin and adjacent Waipapa Group, North Island, NewZealand. New Zealand Journal of Geology and Geophysics42: 469–488.

Reyners, M. 1998: Plate coupling and the hazard of large subductionthrust earthquakes at the Hikurangi subduction zone, NewZealand. New Zealand Journal of Geology and Geophysics41: 343-354.

Richardson, W. P. 1989: The Matata earthquake of 1977 May 31: arecent event near Edgecumbe, Bay of Plenty, New Zealand.New Zealand Journal of Geology and Geophysics 32: 17-30.

Scheibner, E.; Sato, T.; Craddock, C. comp. 1991: Tectonic mapof the Circum-Pacific region, south-west quadrant,1:10 000 000. Circum-Pacific map series. Menlo Park,California, United States Geological Survey. 1 sheet + 59 p.

Dow

nloa

ded

by [

Uni

vers

ity o

f In

carn

ate

Wor

d] a

t 06:

34 3

0 O

ctob

er 2

014

374 New Zealand Journal of Geology and Geophysics, 2004, Vol. 47

Schofield, J. C. 1958: Notes on volcanism and structure in FranklinCounty. New Zealand Journal of Geology and Geophysics1: 541-559.

Shane, P.; Black, T.; Eggins, S.; Westgate, J. 1998: Late Miocenemarine tephra beds: recorders of rhyolitic volcanism inNorth Island, New Zealand. New Zealand Journal ofGeology and Geophysics 41: 165-178.

Skinner, D. N. B. 1986: Neogene volcanism of the Hauraki VolcanicRegion. Royal Society of New Zealand Bulletin 23: 21-47.

Smith, E. G. C.; Oppenheimer, C. M. M. 1989: The Edgecumbeearthquake sequence: 1987 February 21 to March 18. NewZealand Journal of Geology and Geophysics 32: 31-42.

Smith, I. E. M.; Ruddock, R. S.; Day, R. A. 1989: Miocene arc-type volcanic/plutonic complexes of the NorthlandPeninsula, New Zealand. Royal Society of New ZealandBulletin 26: 205-213.

Smith, I. E. M.; Okada, T.; Itaya, T.; Black, P. M. 1993: Agerelationships and tectonic implications of late Cenozoicbasaltic volcanism in Northland, New Zealand. NewZealand Journal of Geology and Geophysics 36: 385-393.

Spörli, K. B. 1989: Tectonic framework of Northland, New Zealand.Royal Society of New Zealand Bulletin 26: 3-14.

Stern, T. A. 1986: Geophysical studies of the upper crust withinthe Central Volcanic Region, New Zealand. Royal Societyof New Zealand Bulletin 23: 92-111.

Stevens, G. R. 1980: New Zealand adrift. Wellington, New Zealand,Reed. 442 p.

Stipp, J. J. 1968: The geochronology and petrogenesis of theCenozoic volcanics of the North Island, New Zealand.Unpublished PhD thesis, lodged in the Library, AustralianNational University, Canberra, Australia.

Stirling, M. W.; Wesnousky, S. G.; Berryman, K. R. 1998:Probabilistic seismic hazard analysis of New Zealand. NewZealand Journal of Geology and Geophysics 41: 355-375.

Suggate, R. P.; Stevens, G. R.; Te Punga, M. T. ed. 1978: The geol-ogy of New Zealand. 2 vol. Wellington, GovernmentPrinter.

Thompson, B. N. 1964: Quaternary volcanism in the Central Vol-canic Region. New Zealand Journal of Geology and Geo-physics 7: 45-66.

Thompson, B. N.; Kermode, L. O.; Ewart, A. ed. 1966: New Zea-land volcanology—Central Volcanic Region. New ZealandDepartment of Scientific and Industrial Research Informa-tion Series 50. 211 p.

Villamor, P.; Berryman, K. 2001: A late Quaternary extension ratein the Taupo Volcanic Zone, New Zealand, derived fromfault slip data. New Zealand Journal of Geology andGeophysics 44: 243-269.

Walcott, R. I.; Mumme, T. C. 1982: Paleomagnetic study of theTertiary sedimentary rocks from the East Coast of the NorthIsland, New Zealand. New Zealand Department of Scientificand Industrial Research Geophysics Division Report 189.44 p.

Watters, W. A. 1986: Comments on possible provenance of pebblesin Ihungia Formation conglomerate. New ZealandGeological Survey Sheet File Y16/572. 5 p.

White, S. R. 2002: The Siberia Fault Zone, northwest Otago, andkinematics of mid-Cenozoic plate boundary deformationin southern New Zealand. New Zealand Journal of Geologyand Geophysics 45: 271-287.

Wilson, C. J. N. 1986: Reconnaissance stratigraphy andvolcanology of ignimbrites from Mangakino Volcano.Royal Society of New Zealand Bulletin 23: 179-193.

Wilson, C. J. N.; Houghton, B. F.; Lloyd, E. F. 1986: Volcanichistory and evolution of the Maroa-Taupo area, centralNorth Island. Royal Society of New Zealand Bulletin 23:194-223.

Wilson, J. T. 1963: Evidence from islands on the spreading of theocean floor. Nature 207: 343-347.

Dow

nloa

ded

by [

Uni

vers

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ate

Wor

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