This article was downloaded by: [Uniwersytet Warszawski]On: 18 October 2014, At: 05:45Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

New Zealand Journal ofGeology and GeophysicsPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/tnzg20

Rhyolitic tephra marker bedsin the Tongariro area, NorthIsland, New ZealandW. W. Topping a & B. P. Kohn aa Department of Geology , Victoria University ofWellington , New ZealandPublished online: 14 Feb 2012.

To cite this article: W. W. Topping & B. P. Kohn (1973) Rhyolitic tephra marker beds inthe Tongariro area, North Island, New Zealand, New Zealand Journal of Geology andGeophysics, 16:3, 375-395, DOI: 10.1080/00288306.1973.10431367

To link to this article: http://dx.doi.org/10.1080/00288306.1973.10431367

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 375

RHYOLITIC TEPHRA MARKER BEDS IN THE TONGARIRO AREA, NORTH ISLAND, NEW ZEALAND

W. W. ToPPING and B. P. KoHN

Department of Geology, Victoria University of Wellington, New Zealand

(Received 31 January 1973)

ABSTRACT

In the Tongariro area 13 rhyolitic tephras erupted from Okataina, Maroa, and Taupo Volcanic Centres over the last 20 000 years are interbedded with local andesitic tephras. The order of succession of the 13 tephras is established by stratigraphy, and is confirmed by their mineralogical composition and by chemical analysis of their titanomagnetites. Seven of the rhyolitic tephras have been previously dated by 14C, four are dated here, and two are not yet dated. The four new 14C dates provide ages of c. 12 500 years B.P. for Rotorua Ash (NZ 1186, NZ 1187); 9785 ± 170 years B.P. for Papanetu Tephra and Karapiti Lapilli (NZ 1372, NZ 1374); and c 9740 years B.P. for Poronui Tephra.

INTRODUCTION

Andesitic tephras erupted from the Tongariro National Park volcanoes (Fig. 1) have been studied during the course of regional geological mapping (Grange & Hurst 1929; Grange & Williamson 1930; Gregg 1960) and soil mapping (Grange 1931; Grange & Taylor 1931; New Zealand Soil Bureau 1954). Only the youngest tephras have been formally named and mapped in any detail. Ngauruhoe Ash (Grange & Hurst 1929, p. 6) was mapped by Grange (1931) as a soil-forming ash and includes all andesitic ash from the Tongariro Volcanic Centre (Grindley 1960) above the rhyolitic Taupo Pumice (Baumgart 1954; Healy 1964). Gregg (1960) formally named the Mangatawai Ash for " ... thinly bedded dark-grey andesite ash containing leaves ... " (Grange & Hurst 1929, p. 7) immediately underlying Taupo Pumice. Tongariro Ash was a comprehensive name for andesitic tephra older than Mangatawai Ash (Gregg 1960, p. 38).

Individual beds within the Tongariro Ash are "confusingly alike" (Gregg 1960, p. 38). Where stratigraphic sections are close together, the andesitic tephras can be correlated without difficulty, but where sections are more than 0·5 km apart the similarity in appearance and complex distribution pattern of andesitic lapilli units makes correlation difficult.

The only rhyolitic tephras previously identified within the Tongariro tephra sequence have been Taupo Pumice (Baumgart 1954; Healy 1964) and Oruanui Formation (Vucetich & Pullar 1969). Gregg (1960) noted that other rhyolitic tephra occurring within the anqesitic sequence may correlate with Taupo Sub-group members.

Twelve rhyolitic tephras of known age have now been identified within the andesitic tephra sequence, and have proved to be very useful marker beds. Most sections within the Tongariro area contain at least one rhyolitic tephra, and up to seven may be present in any one section. Eight rhyolitic

N.Z. Journal of Geology and Geophysics 16 (3): 375-95

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

376 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

1' N

I

FIG. 1-Locality map of study area. Numbers refer to reference sections (see Appendix): 1-Mangatawai, 2-Access 10, 3-Poutu, 4-Te Ponanga Saddle, and 5-Wairoa

tephras are widespread and useful as markers. The widespread rhyolitic tephras also provide valuable time control in the southern part of the study area, where tephras from Ruapehu are dominant and where tephras from Tongariro are absent. A further fiv,e rhyolitic tephras are present in the area, but appear in too few sections to be of much value. However, the stratigraphic position of these less common tephras adds further time control to the otherwise difficult andesitic sequence.

North of Tongariro, identification of rhyolitic tephras can be made from their stratigraphic position in relation to prominent andesite lapilli beds (Table 1). In the laboratory, identification of rhyolitic tephras has been

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

Nd. 3 ToPPING & KoHN -RHYOLITIC TEPHRAS AT ToNGARIRO 377

TABLE !-Stratigraphic column showing the relationship, in the Tongariro area, of andesitic tephras of the Tongariro Sub-group with interbedded rhyolitic tephras from the Okataina, Maroa and Taupo Volcanic Centres.

FORMATION NAMED MEMBERS UNNAMED SYMBOLS VOLCANIC INFERRED 14C AGES IN YEARS BEFORE Nzl4C NUMBER BEDS CENTRE STRATIGRAPHIC 1950

(SOURCE) AGE (NOT 14c-DATED)

.t.Ngauruhoe Tephra ng Tongariro

.:raupo Pumice Upper Tau o Pumice ' 1 Taupo Lapilli 'P 3 Taupo 1,819:!:17 Averaged from many Rotongaio Ash 'P 4 dates (Healy 1964)

'Putty Ash' 'P 5

3Mangatawai Tephra mg Tongariro 2, 500 :!: 200 (basal 80 mm) NZ186

Andesitic tephra

4Whakaipo Tephra Taupo 2,670 ±50 (above ash) NZ1070 2, 730 :!: 60 (below ash) NZ1071

Andesitic tephra

:.!Waimihia Waimihia Lapilli Taupo 3,170 ± 80 (above ash) NZ504 3,440 :!: 80 (below ash) NZSOS

Spapakai Tephra pp Tongariro

Hinemaiaia Ash hn Taupo 6, 390 ± 120 (above ash) NZ1137 6,190 ::!: 70 (belov ash) NZ1247

Papakai Tephra pp Tongariro

Rotoma Ash Okataina 7,330!"235 NZ1199 Papakai Tephra pp Tongariro

Opepe Tephra op Taupo 8,850 ± 1000 :\Z1S5 Papakai Tephra PP Tongariro

5Mangamate Tephra Poutu Lapilli P' Tongariro 9,700 Andesitic Tongariro teohra

Poronui Tephra po Taupo 9,740

.:>Mangamate Andesitic Tongariro Tephra tephra

Te Rato Lapilli Tongariro 9, 700 ± 200 (below lapilli) NZ1373 9, 780 ± 170 ( .. .. ) Nll372

Papanetu Tephra P• Taupo 9,785

4Karapiti Lapilli kp Taupo 9,790

Sokupata Tephra I Unnamed ash Basal oa Tongariro 9, 790 :!: 160 (above ash) NZ1374

lapilli Andesitic Tongariro tephra

6? Rotorua Ash Okataina 12,500 12,350 ± 220 (above ash) NZll87 13,150 + 300 (below ash) !iZlH!6

Andesitic Tongariro tephra

? Puketarata Ash pk Maroa 13,500

Andesitic Tongariro tephra

.:>Rotoaira Lapilli Tongariro 13,800 ± 300 (below l,apilli) !\Zl559

Andesitic Tongariro tephra

6Rerewhakaaitu Ash rk Okataina 14, 700 ± 200 (below ash) :-.z716

Andesitic Tongariro

tephra

8oruanui Formation Oruanui Jlreccia 7 Maroa

Oruanui Ash 20,670 ± 300 (within ash) Nll2 19,850 ± 310 (below ash) N41055

1 Named by Grange & Hurst (1929) 5 Named by Topping (1973)

Baumgart (1954) Vucetich & Pullar (1964)

Gregg (1960) .. Lloyd (1972)

Vucetich & Pullar (1973) .. Vucetich & Pullar (1969)

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

378 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

determined by radiocarbon dating of associated organic matter, heavy mineral determinations, and chemical analysis of titanomagnetites within the tephra (Kohn 1970).

The identification of rhyolitic tephras provides a time-stratigraphic column (summarised in Table 1) for tephras in the Tongariro area. The established chronology therefore allows dating of other important late Quaternary events.

IDENTIFICATION AND CORRELATION OF RHYOLITIC TEPHRAS

Radiocarbon Dating Seven new radiocarbon dates from sites north-west of Tongariro provide

ages for four rhyolitic tephras not previously dated. Papanetu Tephra, brac~eted by two radiocarbon dates (NZ 1372, NZ 1374; see Table 2), is assigned an age of 9785 years B.P. Papanetu Tephra was erupted im­mediately following eruption of Karapiti Lapilli (Vucetich & Pullar 1973) and therefore the age of Karapiti Lapilli is also about 9785 years B.P. An ash considered to be Rotorua Ash (Vucetich & Pullar 1964) is bracketed by two radiocarbon dates (NZ 1187, NZ 1186; see Tab1e 2), and is estimated to be 12 500 yr B.P.

Two wood samples from peat in a swamp cut by the Otamangakau Canal (N112/109984)*, which underlies Taupo Pumice, and the age of the pumice itself, indicate that the peat accumulated uniformly at approximately 0·45 m per thousand years. The rate is used to date two interbedded tephras and one basal tephra not previously dat,ed. The results are shown below:-

Tephra

Rotoma Ash (Vucetich & Pullar 1964)

Opepe Tephra (Vucetich & Pullar 1973)

Poutu Lapilli (Topping 1973)

Ages from rate of peat accumulation

7430 yr B.P.

8600 yr B.P.

9700 yr B.P.

Previous dates

7330 yr B.P. (Pullar & Heine 1971)

8850 yr B.P. (Healy 1964)

Poronui Tephra (Vucetich & Pullar 1973) lies between Poutu Lapilli and Papanetu Tephra, so that its age is estimated to be 9740 years B.P.

Ferromagnesian Assemblages and Chemical Analysis of Titanomagnetites Rhyolitic tephras of the Taupo Sub-group (Healy 1964) contain a

ferromagnesian assemblage of dominantly hypersthene with or without (-+-) augite, and with very rare hornblende, biotite and olivine (Ewart 1963).

The Rotorua Sub-group tephras (Vucetich & Pullar 1964) include three different ferromagnesian assemblages (Ewart 1966; Cole 1970; Kohn 1973),

*Grid reference based on the national thousand-yard grid of the 1 :63 360 topographical map series (NZMS 1).

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

TABLE 2-Radiocarbon ages for rhyolitic tephras present in the Tongariro area and associated andesitic tephras.

FOSSIL RECORD NO, r-.:zl4c NO.

Nll2/544 N~l335

Nll2/545 Nll:335

Nll2/55l KZ1373

Nll2/550 NZ1372

Nll2/552 NZ1374

Nl12/539 NZ1187

Nll2/540 KZ1186

Nll2/548 ,NZ1559

14c AGE YEARS Jl,P,(l950)

3,200! 50

9,560:!: 100

9,700 ~ 210

9, 780: 170

9, 790::: 160

12,350 :- 220

13,150:!: 300

13,800 '!:: 300

EVENfS AGED

Provides check on rate of accumulation of peat and thus a more accur­ate estimate of age of Pou tu La pi 11 i

Minimum age for Poutu Lapilli

Maximum Te Rato Lapilli; for Papanetu Tephra and Karapiti Lapilli

Maximum for Papanctu Tephra

Provides a minimum age for '! Rotorua Ash

Provides a maximum age for ? Rotorua Ash

Maximum age for Rotoaira Lapilli

All samples collected by W.W. Topping

~~~~~iG~~~~~p~~~~~ION 1 (N~t~iAzg~8 )Y'~

Wood= within peat; 0,66 m below ba:,e I NllZ/109984; swamp cut by of Taupo Pu1nice, 3,46 m above Poutu Canal, Tongariro Power Scheme Lapilli

Woodl small branches from peat 4.03 m below Taupo Pumice and 90 mm above Poutu Lapilli

Peat: 5 mm horizon below Te Rato Lapilli and above Papanetu T('phra

Wood: twigs from 5 mm horizon of peat sepdrating Te Rato Lapilli from ~-underlyir:g Papanetu Tephra

Wood: twies from 20 mm of peat below Papanctu Tephra

'! Rotorua Ash

c'harcoal: scattered throughout top third of an andesitic tephra unit which in neighbouring sections is 0.13 m below ? Roturua Ash

Charcoal: within andesitic tephra immediately underlying Rotoaira Lapilli Formation

Toneariro, Nll2/145983; swamp cut by Wairehu Canal, Tongariro Power Scheme. Approx. 0.9 km NW of p<Jint where Rotaira Road crosses canal

Nll2/l05987; 450 m cast of Trir;, ~0 m west of Tonr;ariro Power

Scheme Access Road No, f~

Tongarirol Nll2/298951; cutting on eastern side of Dc>sert Road, east of Pihanga and 6.4 km south of Turanr;i

z ?-1.»

S1 'tl 'tl z Cl

Pi'

~ :I: z I

~ t'"' :::; (:;; ...., tT1 'tl

sa > (/)

~

~ z ~ ~

1.» -..j \0

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

380 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

TABLE 3-Dominant ferromagnesian assemblages for rhyolitic tephras identified in the Tongariro Volcanic Centre.

----- ------ -----

Hypersthene ± augite

Taupo Pumice

Whakaipo Tephra Waimihia Lapilli

Hinemaiaia Ash Opepe Tephra Poronui Tephra Papanetu Tephra Karapiti Lapilli

Hypersthene + calcic hornblende

± cummingtonite

Biotite + hypersthene ± calcic hornblende

±augite

Oruanui Formation (may con- ?Rotorua Ash tain augite)

?Puketarata Ash ?Rotoma Ash (contains bio- Rerewhakaaitu Ash tite where sampled in Tonga-rim region)

i.e., (a) hypersthene -+- augite; (b) hypersthene + calcic hornblende -+­cummingtonite; and (c) biotite + hypersthene ± calcic hornbiende -+­augite.

The Oruanui Formation erupted from north of Lake Taupo (Vucetich &

Pullar 1969) contains a ferromagnesian assemblage of hypersthene + calcic hornblende -+- sparse augite -+- rare biotite.

Taupo Sub-group tephras (i.e., erupted from Taupo Volcanic Centre), in containing v,ery rare biotite and calcic hornblende, can generally be distinguished from tephras erupted from the other sources, but the uniformity of the ferromagnesian assemblage does not allow identification of individual formations (Table 3). The chemical analysis of titanomagnetites (Kohn 1970) was used to distinguish younger and older Taupo Sub-group tephras, and also to confirm correlation of rhyolitic tephras from other centres.

Rhyolitic tephras sampled for chemical and mineralogical analysis were taken from the middle of oockets and lenses, and were considered to be least contaminated. •

Titanomagnetite analyses are presented in Table 4.

DESCRIPTIONS OF RHYOLITIC TEPHRAS

Taupo Pumice ( tp)

Taupo Pumice has long been recognised as an important and widespread deposit in the study area, and was once believed to have been erupted from the Tongariro volcanoes (Dieffenbach 1843, p. 128; Wakefield 1845, p. 236; Taylor 1855, p. 225). Gregg (1960, p. 39) summarised previous work and showed its distribution by a generalised isopach map. However, within the Tongariro area varying amounts of primary deposits (airfall and nuee ardente ori~in, almost certainly erupted from more than one source) and water-sorted pumice make the distribution pattern more complex.

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN- RHYOLITIC TEPHRAS AT ToNGARIRo 381

In the nothern part of the area two further members of the Taupo Pumice Formation are present. Rotongaio Ash (Baumgart, 1954; Healy, 1964), with its distinctive steel-grey colour, is 5-20 mm thick at sections near Kuratau (see Fig. 1), and also about 20 mm thick on Kepa Road, east of Turangi (N102/382012). At the latter locality 20 mm of cream­coloured ash ("Putty Ash", Tsg member 5; Healy 1964) underlies Rotongaio Ash, but has not been seen further south.

According to Gregg (1960) the Taupo Pumice defines the top of the Mangatawai Ash and the base of the Ngauruhoe Ash.

Whakaipo Tephra (wo)

Whakaipo Tephra (Vucetich & Pullar 1973) can be identified in the northern part of the region studied, where it is of lapilli grade. On Kepa Road (N102/382012), 90 mm of pale yellow Whakaipo Tephra occurs within Mangatawai Ash 0·16 m above Waimihia Lapilli. Further south, the Mangatawai Ash separating them becomes indistinct, so that Whakaipo Tephra cannot be distinguished from Waimihia Lapilli. Still further south (N122/223671) Whakaipo Tephra is significantly finer.

Correlation was established by stratigraphy and presence of hypersthene + augite. Titanomagnetite was not analysed.

Waimihia Lapilli (wm)

Waimihia Lapilli (Baumgart 1954; Healy 1964) can be identified up to 9 km south-west of Ruapehu (N121/993595) and in the southern area of the Rangipo Desert (N122/165595, 10 km south-east of Ruapehu). It has not been found to the west of the volcanoes.

In the south (N122/097565) the ash is fine and yellow to pale yellow, and forms a well defined horizon up to 50 mm thick. About 34 km further north-east, where Waimihia Lapilli is of less use as a marker, it consists of 0·3 m of medium pale pumiceous ash scattered throughout fine yellowish brown ash.

The ferromagnesian assemblage (hypersthene + augite) and the relatively high titanium, chromium and zirconium, and low vanadium, cobalt and nickel of the titanomagnetites confirms identification as Waimihia Lapilli (*Table 4, analyses 8-13). It is distinguished from the otherwise minera­logically and chemically similar Taupo Pumice by its relatively high zirconium content ( > 100 ppm).

Hinemaiaia Ash (hn)

Fine white rhyolitic tephra interbedded with the Papakai Tephra (see Table 1), and occurring at all sections along the Desert Road from Maka­hikatoa Stream bridge (N112/250787) south to Mangatoetoenui Stream (N112/216709), is correlated with Hinemaiaia Ash (Vucetich & Pulla::

*All analysis Nos. refer to analyses given in Table 4.

Gcology-5

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

TABLE 4-Titanomagnetite analyses of rhyolitic tephras from near source and within Tongariro area. Analyses involved apparatus and operating conditions described by Kohn ( 1970, and are the averaged result of samples generally run in triplicate. The analytical precision, expressed as relative deviation, was ± 10%. Numbers prefixed by P refer to the petrological collection of the N.Z. Geological Survey.

Analysis Sam.ple No.

Locality Grid Ref. Ti Mg "/• Mn

Taupo Pumice Napier-Taupo Highway; N94/564354 7. 92 I. 06 0, 69 basal 30 em

Taupo Pumice Wairakei-Putaruru High- N94/516544 7. 92 0. 69 0. 80 way (Route 1)

Taupo Pumice Old Ketatahi Track N112/133894 7. 63 0. 89 0. 92

4 Taupo Pumice Cutting near Waikato Falls NllZ/309830 7. 87 0. 75 0. 66

10

11

12

13

14

15

16

17

18

19

20

Taupo Pumice Top of Pukeonake Cone NllZ/066824

Mapara Tephra Burrows Quarry; N94/647394 basal 15 em lapilli

V\bakaipo Tephra Mapara Road; N94/466364 basal 15 em pumice blocks

Waimihia Lapilli Napier-Taupo Highway; N94/572354 basal 20 em pumice blocks

Wain:ilia La.pilli Wairakei-Putaruru High- N94/516544 way (Route 1 )

Waimihia Lapilli Ohakune Mountain Road NlZl/996602

Waimihia Ash liangipo Desert NlZZ/165595

Waimihia Ash West Taupo Road N102/179194

Waimihia Ash Desert Road Nl22/219675

Hinemaiaia Ash P28856 N94/587347

Hinemaiaia Ash National Park .. Taupo Road Nll2/125924

Opepe Tephra Napier .. Taupo Highway N94/572354

Poronui Tephra P28866 N94/587347

Poronui Tephra Iwatahi Gully: N103/735200 basal 15 em lapilli & ash

Poronui Tephra Desert Road Nll2/298951

Poronui Tephra Above Taupo .. Turangi Road

N102/341070

7. 41 o. 82

7.55 0.90

8.45 o. 50

7.28 1,23

8.02 0.78

9.17 o. 72

7. 61 o. 62

7.34 0,68

10,44 1,29

8. 08 o. 55

6. 55 o. 59

7.24 o.so 7. 81 o. 76

7.02 0.67

6. 25 o. 90

6.10 0.72

o. 59

0.87

o. 70

o. 79

o. 89

o. 55

0, 63

o. 69

0, 77

0,82

o. 65

o. 59

o. 61

0.47

0. 52

o. 53

Ca

o. 54

o. 66

o. 77

o. 74

o. 51

o. 30

0,35

o. 67

0.46

o. 06

0.17

0.16

o. 25

o. 29

o. 08

o. 37

0.18

o. 24

o. 23

0,13

v

649

847

968

1043

896

633

443

699

1023

1008

709

714

989

887

762

3470

3066

3602

2804

2960

Cr

131

117

162

143

220

106

73

149

135

201

128

95

136

85

99

11'(

114

131

113

102

Co ppmNi Zr Cu

16 27

35 55

50 55

50 58

51

33

35

24

55

43

30

40

50

44

34

69

75

75

82

76

85

41

24

27

68

75

36

38

87

55

35

87

99

110

99

90

68

83

78

82

60

71

454

332

380

226

222

239

225

663

176

226

280

136

497

584

22

43

68

65

100

39

61

41

60

99

42

98

126

50

80

59

56

78

59

107

"" 00 N

z ~ ._ 0

~ z :> t'"

0 >,j

~ 0 t'" 0

~ :> z 0

~ 0

~ [f)

r; [f)

~ t'"

...... G\

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

Poronui Tephra Head of Waipakihi River

Papanetu Tephra Top of Kuharua Dome

Papanetu Tephra Te Ponanga Road

Papanetu Tephra Te Ponanga Road

Karapiti La.pilli Iwatahi Gully basal 5 em lapilli & ash

Karapiti Lapilli P28865

Rotorua Ash Rotorua-Taupo Highway basal 15 em lapilli & ash

Rotorua Ash

Rotorua Ash

Lynmore Hill 20 em from top- ash

Road west side Lake Rotorua; basal pUinice blocks

N112/431846

NlOZ/188082

N112/224983

Nl 02/256015

Nl03/735200

N94/587347

N76/780908

N76/774010

N76/677135

? Rotorua Ash

? Rotorua Ash

Cutting near Waikato Falls NllZ/301844

Mangatepopo Track N112/069798

?Rotorua Ash Otamangakau Canal NllZ/105979

Puketarata Ash Wairakei-Putaruru High- N94/ 516544 way (Route l)

?Puketarata Ash Desert Road

Rerewhakaaitu Ash

Rerewhakaaitu Ash

Rerewhakaaitu Ash

Democrat Road basal 15 em ash

Gavin Road

~;~~~i~g~) Valley

Nll2/250806

N86/934824

N86/995824

N112/089823

?Rerewhakaaitu National Park-Taupo ~oad NllZ/239901 Ash (contaminated)

Oruanui Ash

Oruanui Ash

Wairakei-Putaruru High- N94/523521 way (Route 1) basallapilli Braemar Road N68/202265 12 em from top

Oruanui Ash Rangipo Desert Nl22/175575

Oruanui Breccia NE side Ton~ariro River NlOZ/303015

8.78 0.75

7.34 1.0~

6. 91 o. 90

6.30 1,10

6.92 0,87

7.43 0.67

4.21 0.98

4.99 0.93

5. 29 o. 92

4. 69 l, 04

4. 99 l, 01

5, 79 o. 98

6.39 0,43

5. 39 o. 66

4.79 0.61

5. 34. o. 45

5. 06 o. 54

6. 67 o. 73

6. 17 o. 62

5.30 0,80

6.47 l. 01

5. 78 o. 75

o. 38

0, 37

o. 50

0.43

o. 54

o. 57

o. 59

o. 62

o. 64

0, 51

o. 59

o. 63

o. 78

o. 7l

o. 71

o. 62

o. 70

o. 62

0.44

o. 55

o. 51

o. 63

0. 08

0.10

o. 09

o. 08

0,10

0.14

o. 63

o. 06

0.41

o. 07

0.18

0.10

o. 50

0.13

o. 11

o. 24

o. 09

0.10

0.16

0.11

o. 30

0.86

3039

3531

3889

4044

3906

3090

2039

2364

2398

3178

2633

2968

1936

1923

2122

1920

2245

3389

2714

2963

3292

3559

146

710

285

462

179

111

124

161

143

492

532

454

179

141

149

151

142

351

195

261

250

239

66

127

101

113

75

76

48

75

48

82

84

94

82

60

58

35

53

80

75

90

85

72

113

179

163

179

115

114

56

67

43

150

119

155

79

66

67

33

46

103

69

115

109

100

1~3

114

284

217

192

350

524

639

453

394

270

3,37

435

409

733

684

451

602

184

391

223

418

74

72

133

107

64

50

20

22

43

36

52

112

56

83

41

20

34

76

36

95

70

63

z 0

<.»

2 "C "C z Cl

fll'

s ::t: z I

~ C5 t"' ::::; c=; ...., tn "C sg > (fJ

::; 2 z ~ :;; 0

<.» 00 <.»

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

384 N.Z. JOURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

1973). Between these localities the ash typically occurs about 0·15 m above Poutu Lapilli and about 0·5 m below the top of Papakai Tephra (Topping 1973). Near Makahikatoa Stream, Hinemaiaia Ash occurs as "cream cakes" (Healy 1964, p. 10) or in isolated pockets. Further south, and due east of the Tama Lakes, it forms a continuous horizon. It is suggested that the continuous eruption of andesitic tephra from one of the Tongariro vents protected Hinemaiaia Ash from subsequent erosion or disturbance during soil-forming processes.

North of Tongariro, Hinemaiaia Ash occurs in only a few sections. On an old Ketetahi Springs track (N112/135915) it is 50 mm thick and 50 mm above the base of the 0·73 m-thick Papakai Tephra. About 1·3 km WNW (N112/125924), it occurs as an isolated pocket, 60 mm thick, in the lower part of the Papakai Tephra. The occurrence of Hinemaiaia Ash to the north of Toagariro, in pockets only rather than as a continuous horizon, indicates little protection from erosion by subsequent andesitic tephras.

According to the stratigraphic position and ferromagnesian mineral content (hypersthene + augite) the ash could be Hinemaiaia Ash or Opepe Tephra. However, the titanomagnetite analysis (analysis 15) identifies the ash as Hinemaiaia Ash.

? Rotoma Ash (rm)

The rhyolitic ash scattered through 20 mm of peat in the swamp cut by the Otamangakau Canal (N112/109984) has an age, by interpolation, of 7430 years B.P. According to Pullar & Heine (1971), Rotoma Ash has an age of 7330-+- 235 years B.P. (NZ 1199). The ferromagnesian assemblage of a sample from the peat comprises hypersthene + biotite + calcic-hornblende + augite. That for the Rotoma Ash (Vucetich & Pullar 1964) comprises calcic hornblende + hypersthene + rare augite. The amount of biotite in the sample from the swamp is anomalously high. Most of the augite in the sample from the peat is larger in size than the other ferromagnesian minerals, and is probably contamination from andesitic tephras. The age, and presenoe of calcic hornblende, suggests correlation with Rotoma Ash.

Opepe Tephra ( op)

Opepe Tephra (Vucetich & Pullar 1973) is only recognised in a peat swamp cut by the Otamangakau Canal (N112/109984). The estimated age from the uniform rate of peat accumulation is 8600 yr B.P., which compares well with a radiocarbon age of 8850 -+- 1000 yr B.R (Healy 1964). The deposition of Opepe Tephra occurred at the time of maximum soil develop­ment on Papakai Tephra, making its preservation outside of peat swamps very unlikely.

Porontti Tephra (po)

Poronui Tephra (Vucetich & Pullar 1973) is a rhyolitic tephra erupted from Taupo Volcanic Centre. North of Tongariro, Poronui Tephra is en­closed by Poutu Lapilli and Te Rata Lapilli, but to the east TeRata Lapilli is thin or absent.

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN -RHYOLITIC TEPHRAS AT ToNGARIRO 385

FIG. 2-Poutu reference section on National Park-Taupo Road (N112/239901), showing four rhyolitic tephras: Taupo Pumice (tp), Poronui Tephra (po), ?Rotorua Ash (rr), Oruanui Formation (ou); and two andesitic marker beds: Poutu Lapilli (pt) and Rotoaira Lapilli (rt).

Poronui Tephra is typically exposed in the Poutu Canal-eastern National Park-Taupo Road region, where it comprises fine yellow ash 10-30 mm thick. It is also present at reference sections Poutu (Fig. 2), Access 10, and Te Ponanga Saddle (Fig. 3), (see Appendix), and extends southwards over half the length of the Desert Road, but does not occur to the west of Tongariro. It thickens northwards to 60 mm on Kepa Road (N102/382012), and eastwards to 80 mm at the head of the W aipakihi Valley (N112/431846).

A 14C age of 9780 -+- 170 yr B.P. forTe Rato Lapilli (NZ 1372; Table 2), together with an estimated age of 9700 yr B P. for Poutu Lapilli, dates Poronui Tephra at about 9740 yr B.P. The preservation of Poronui Tephra as a discrete horizon is attributed to the rapid deposition of overlying andesitic beds.

The ash has been traced northwards and correlated with Poronui Tephra of the Taupo Sub-group. The ferromagnesian assemblage (hypersthene + augite) confirms this correlation. Titanomagnetite analyses of Poronui Tephra at the Iwatahi reference section (N103/735200; see Fig. 1) and one other site (analyses 17, 18) correlate with the rhyolitic ash bracketed by Poutu Lapilli and Te Rato Lapilli at three sites in the Tongariro region (analyses 19-21). At the lwatahi l'eference section, Poutu Lapilli has been identified in the paleosol of Poronui Tephra, which is in turn underlain by the grey­green Te Rata Lapilli.

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

386 N.Z. JouRNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

. FIG. 3-Te Ponanga Saddle reference section, Te Ponanga Saddle Road (N112/ 224983 ), typ~ section for Paoanetu Tephra. Rhyolitic t~phras are: Waimihia Lapilli (wm), Poronui Tephra (po), Papanetu Tephra (pa), ?Puketarata Ash (pk); the andesitic units are: Poutu Lapilli (pt) and TeRata Lapilli (tt).

Papanetu Tephra (pa)

Papanetu Tephra is a new formation name for rhyolitic tephra immediately underlying the Te Rato Lapilli. At the type section on the Te Ponanga Saddle Road (N112/224983; see Appendix), Papanetu T~ephra comprises up to 20 mm pale yellow ash with abundant grey lithic fragments, and clear obsidian up to 10 mm. On Kuharua Dome (N102/188082) Papanetu Tephra, below Te Rata Lapilli and above rhyolitic breccia, comprises 0·62 m of rhyolitic ash and coarse obsidian fragments.

The tephra is best displayed in sections along Te Ponanga Saddle Road, where it is commonly 10-20 mm thick but with a range of 2-40 mm. The isopach pattern (Fig. 4) and the coarse obsidian fragments indicate that the source is Kuharua Dome.

Papanetu Tephra is brac~eted by two new radiocarbon dates. Twigs from 5 mm of peat above Papanetu Tephra gave an age of 9780 + 170 years B.P.

(NZ 1372, Table 2), the peat gave an age of 9700 + 210 years B.P. (NZ 1373, Table 2), and twigs from 20 mm of peat immediately underlying the tephra gave an age of 9790 + 160 years B.P. (NZ 1374, Table 2). The age of Papanetu Tephra is taken as being 9785 years B.P., and the date provides a minimum age for Kuharua Dome.

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN- RHYOLITIC TEPHRAS AT ToNGARIRO 387

FIG. 4-Isopach map of Papanetu Tephra (based on 77 measurements). All thicknesses are in mm.

Papanetu Tephra has a ferromagnesian assemblage comprising hypersthene + augite. ThDee titanomagnetite analyses, including one from the section on Kuharua Dome, are similar except that chromium is higher in the sample from the dome (seeTable4).

Karapiti Lapilli (kp)

Rhyolitic tephra correlated with Karapiti Lapilli (Vucetich & Pullar 1973) underlies Te Rata Lapilli on Kepa Road and at sections further north. Karapiti Lapilli and Papanetu Tephra both directly underlie Te Rato Lapilli, without evidence of significant time break. The age of Karapiti Tephra is therefore considered to be about 9785 years.

Two titanomagnetite samples of Karapiti Lapilli were analysed (analyses 25, 26) and found to be significantly lower in chromium, cobalt and nickel than Papanetu Tephra samples. Karapiti Lapilli and Papanetu Tephra both have a hypersthene + augite ferromagnesian assemblage, so cannot be distinguished on mineralogy.

? Rotorua Ash (rr)

A fine yellow rhyolitic ash that probably correlates with Rotorua Ash (Vucetich & Pullar 1964) occurs about midway between Te Rato Lapilli and Rotoaira Lapilli in sections to the north of Tongariro, and in about

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

388 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

half of all sections elsewhere in the study area spanning this time range. Th:: ash extends as far westwards as Moerangi and southwards almost to Waiouru (see Fig. 1), and reaches a maximum thickness of 60 mm. It occurs typically as small "cream cakes" (Healy 1964, p. 10), or in small pockets to the north of Tongariro (e.g., at ref,erence sections Poutu, Access 10, and Mangatawai, described in appendix. See also Fig. 5). At sec-tions on the National Park-Taupo Road south of Taurewa it occurs as a discrete horizon where overlain by tephra from Mt Ruapehu.

Its wide distribution and its fine grain size suggests a distant source. Two dated andesitic tephras (12 350 + 220 years B.P., NZ 1187; 13 150 + 300 years B.P., NZ 1186; Table 2) from a section at N112/105987 can be cor­related with a section 0·5 km to the north-west (N112/102990), where they bracket the rhyolitic ash, and indicate an age of about 12 500 years B.P. The ferromagnesian assemblage comprising hypersthene + calcic hornblende + biotite + augite sug~ests correlation with a Rotorua Sub-group tephra, and the Rotorua Ash, with an estimated age of 13 000 years B P. (Vucetich &

Pullar 1964), is a probable correlative.

Three titanomagnetite analyses (analyses 30-32), from the Tongariro region contain si~nificantly higher vanadium, chromium, cobalt and nickel than three near-source Rotorua Ash samples (analyses 27-29). However, the presence of some very lanse augite and hypersthene in the Tongariro samples may indicate contamination by andesitic tephra.

This tephra constitutes the most valuable time plane in the Tongariro area.

? Puketarata Ash (pk)

At the Mangatawai reference section (N112/250806) a rhyolitic tephra comprising a calcic hornblende + hypersthene + minor biotite ferromag­nesian assemblage occurs in a ],ens 0·19 m thick and 1·46 m long, 0·53 m below ?Rotorua Ash and above Rotoaira lapilli (Topping 1973). The stratigraphic position, ferromagnesian assemblage, and titanomagnetic composition (analyses 33, 34) identify the tephra as ? Puketarata Ash.

At a section near Wairehu Canal (N112/145983), a rhyolitic tephra con­taining a biotite + hypersthene + minor calcic hornblende and augite, and occurring between ? Rotorua Ash and Rotoaira lapilli, is also considered to be ? Puketarata Ash. Rerewhakaaitu Ash (see below) has been correlated with a tephra occurring below Rotoaira lapilli at the Te Ponanga Saddle reference section, so that the correlation with Puketarata Ash is supported by a section at Palmer Road (N94/542499) where Puketarata Ash is bracketed by Rotorua and Rerewhakaaitu Ashes (Kohn 197 3).

Isopachs for Puketarata Ash (lloyd 1972) show traces of the ash at Wairakei, but a consideration of the exponential fallout pattern of tephra suggests that it may have been deposited as far south as Tongariro.

Rerewhakaaitu Ash (rk)

A 40 mm lens of white to pale yellow fine rhyolitic ash occurs within andesitic tephras 1 m below ? Rotorua Ash in a section on the lateral moraine on the northern side of Mangatepopo Valley (N112/089822). The ash is

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN -RHYOLITIC TEPHRAS AT ToNGARIRO 389

FIG. 5-Tephra section on eastern side, Motuopuhi Island, Lake Rotoaira (Nl12/198956), showing the rhyo­litic ?Rotorua Ash (rr), Papanetu Tephra ( pa), Poronui Tephra (po), and the andesitic Poutu Lapilli (pt) and Te Rato Lapilli ( tt) . The trowel is 0·29 m in length.

correlated with Rerewhakaaitu Ash (Vucetich & Pullar 1964), erupted from the Okataina Volcanic Centre about 14 700-+- 200 years B.P. (NZ 716).

Rerewhakaaitu Ash is considered to be present as the rhyolitic tephra below Rotoaira Lapilli and above Oruanui Ash at the Te Ponanga Saddle reference section (see Appendix), and 0·15 m below Rotoaira Lapilli at the Poutu reference section.

The ferromagnesian mineral assemblage contains biotite + hypersthene + calcic hornblende -+- augite. Rerewhakaaitu Ash samples from near source have a similar ferromagnesian assemblage, but are not known to contain augite (Cole 1970). Titanomagnetite analysis of the ash (without augite) on the moraine in Mangatepopo Valley agrees well with known Rerewhaka­aitu Ash samples (analyses 3 5-38).

Oruanui Formation ( ou)

The Oruanui Formation occurs throughout the whole region, and its distribution is consistent with an interpolation of Vucetich & Pullar's (1969,

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

390 N.Z. JOURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

p. 798) isopach map. The two members-Oruanui Breccia (tephra-flow) and underlying Oruanui Ash (tephra-fall)-have been radiocarbon dated at 20 600-+- 300 years B.P. (NZ 12; Vucetich & Pullar 1969).

The Oruanui Breccia consists of pale brownish grey massive ash and rare lapilli, and is typically seen on the Rotoaira Road (N112/176979), where the upper 2·7 m is clearly exposed. The contact between the two members is best seen at the Poutu reference section (N112/239901). At a more westerly section (N112/125924) a lens of andesitic boulders and cobbles separates two possible flow units. The possibility of move than one flow unit within Oruanui Breccia could also be explained by slumping after a period of erosion.

The Oruanui Ash is a distinctive air-fall unit containing chalazoidites (Vucetich & Pullar 1969). North of Tongariro, the shower-bedded base of the ash overlies either sands and ~ravels or a very dark brown tuff containing plant fragments.

The two Oruanui members do not occur abov'e an altitude of 1200 m. On the western slopes of Tongariro up to an altitude of 1070 m Oruanui tephra forms the matrix of alluvial deposits, and is interbedded with gravels at a section 13 km SE of Mt Ruapehu (N122/175575). Reworked Oruanui tephra occurs at 1100 mat the head of the Waipakihi Valley (N112/431846), and is 2·4 m thick further down-valley at a height of 1000 m (N112/ 3 77795). The ash occurs up to 670 m altitude on Te Ponanga Saddle Road (N102/238004), while Oruanui Breccia is absent above 580 m (N102/ 244009) in the same area.

The f,erromagnesian assemblages of Oruanui samples in the study area comprise hypersthene + augite + calcic hornblende, which is the same as that for Oruanui tephra in the type area. Titanomagnetite analyses from Oruanui Breccia and Ash (analyses 41, 42) compare well with known samples in the Taupo and Rotorua districts (analyses 39, 40).

REWORKED TEPHRA DEPOSITS

Hinuera Formation

Water-laid pumiceous silts, sands and gravels are exposed in several sections to the north of Tongariro, and vary from large scale current-bedding (as at Poutu reference section) to smaller cross-bedding (as at a section east of Pihanga, N112/298951). It is probably reworked Oruanui Formation, and is considered to correlate with Hinuera Formation (Healy 1946; Thompson 1958; Grindley 1959; Schofield 1965; Vucetich & Pullar 1969; Lloyd 1972).

In all instances within the Tongariro area, Hinuera Formation overlies Oruanui Formation and is in turn overlain by Rotoaira Lapilli (Topping 1973). It is therefore younger than 20 600 years B.P. and older than 13 800 years B.P. (the maximum a~e of Rotoaira Lapilli; Table 2), and can be correlated with Hinuera-2 sediments (Schofield 1965).

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN- RHYOLITIC TEPHRAS AT ToNGARIRO 391

AcKNOWLEDGMENTS

The authors wish to thank New Zealand Radiocarbon Laboratory, Institute of Nuclear Sciences, DSIR, Lower Hutt of 14C datings; Spectrographic Section, Chemistry Division, DSIR for use of equipment for titanomagnetite analysis; Messrs C. G. Vucetich and W. A. Pullar for discussions and access to unpublished data on the Taupo Sub-group; and are indebted to Prof. H. W. Wellman and Dr J. W. Cole for much useful discussion and for critically reading the manuscript. The work was supported by an Internal Research Grant from Victoria University of Wellington.

REFERENCES

BAUMGART, I. 1954: Some volcanic ash showers of the central North Island. N.Z. Journal of Science and Technology B35: 456-67.

CoLE, ]. W. 1970: Description and correlation of Holocene volcanic formati:ns in the Tarawera-Rerewhakaaitu region. Transactiom of the Royal Society of N.Z., Earth Sciences 8 (7): 93-108.

DIEFFENBACH, E. 1843: "Travels in New Zealand". Murray, London. Vol. 1, 431 p.

EwART, A. 1963: Petrology and petrogenesis of the Quaternary pumice ash in the Taupo area, New Zealand. Journal of Petrology 4 (3): 392-431.

---- 1966: Review of the mineralogy and chemistry of the acidic volcanic rocks of the Taupo Volcanic Zone. Bulletin Volcanologique 29: 147-72.

GRANGE, L. I. 1931: Volcanic ash showers. N.Z. Journal of Science and Technology 12: 228-40.

GRANGE, L. I.; HuRST, ]. A. 1929: Tongariro Subdivision. N.Z. Geological Sun;ey 23rd Annual Report: 5-8.

GRANGE, L. I.; TAYLOR, N. H. 1931: Reconnaissance soil survey of the central part of the North Island. N.Z. Geological Survey 25th Annual Report: 7-8.

GRANGE, L. I.; WILLIAMSON, ]. H. 1930: Tongariro Subdivision. N.Z. Geological Survey 24th Annual Report: 10-13.

GREGG, D. R. 1960: The grology of Tongariro Subdivision. N.Z. Geological Surzoey Bulletin 40: 9-152

GRINDLEY, G. W. 1959: Sheet N85 Waiotapu. "Geological rna!' of New Zealand 1: 63 360." N.Z. Department of Scientific and Industrial Research, Wellington.

---- 1960: Sheet 8 Taupo. "Geological map of New Zealand 1: 250 000." N.Z. Department of Scientific and Industrial Research, Wellington.

HEALY, ]. 1946: Geology of the Karapiro District, Cambridge. N.Z. Journal of Science and Technology B27 (3): 199-217.

1964: Stratigraphy and chronology of late Quaternary volcanic ash in Taupo, Rotorua and Gisborne districts. Part 1. N.Z. Geological Surt,ey Bulletin 73: 7-42.

KoHN, B. P. 1970: Identification of New Zealand tephra-layers by emission spectro­graphic analysis of their titanomagnetites. Lithos 3: 361-8.

1973: Studies of N.Z. Quaternary pyroclastic rocks. Unpublished Ph.D. thesis, Victoria University of Wellington Library, New Zealand.

LLOYD, E. F. 1972: Geology and Hot Springs of Orakeikorako. N.Z. Geological Survey Bulletin 85: 164 p.

N.Z. SOIL BuREAU 1954: General survey of the soils of North Island, N.Z. N.Z. Soil Bureau Bulletin 5: 286 p.

PuLLAR, W. A.; HEINE, ]. C. 1971: Ages, inferred from 14C dates, of some tephra and other deposits from Rotorua, Taupo, Bay of Plenty, Gisborne, and Hawke's Bay districts. Proceedings, Radiocarbon Users' Conference, 1!7 el­lington: 117-38.

SCHOFIELD, ]. C. 1965: The Hinuera Formation and associated Quaternary events. N.Z. Journal of Geology and Geophysics 8: 772-86.

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

392 N.Z. JOURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

TAYLOR, R. 1855: "Te Ika a Maui or New Zealand and its Inhabitants'', Wertheim and Macintosh, London. 490 p.

THOMPSON, B. N. 1958: The geology of the Atiamuri dam site. N.Z. Journal of Geology and Geophysics 1: 275-305.

ToPPING, W. W. 1973: Tephrostratigraphy and Chronology of late Quaternary eruptives from the Tongariro Volcanic Centre, New Zealand. N.Z. Journal of Geology and Geophysics (this issue).

VucETICH, C. G.; PuLLAR, W. A. 1964: Stratigraphy and chronology of late Quaternary volcanic ash in Taupo, Rotorua, and Gisborne districts. Part 2. N.Z. Geological Survey Bulletin 7 3: 43-88.

1969: Stratigraphy and chronologv of Late Pleistocene volcanic ash beds in central North Island, New Zealand. N.Z. Journal of Geology and Geophysics 12 (4): 784-837.

1973: Holocene tephra formations erupted in the Taupo area and other interbedded tephras from other volcanic sources. N.Z. Journal of Geology and Geophysics (this issue).

WAKEFIELD, E. ]. 1845: "Adventure in New Zealand, from 1839-1844", John Murray, London. Vol. 2, 546 p.

APPENDIX

REFERENCE SECTIONS

Mangatawai: a cutting on the Waiouru-Turangi Road (Desert Road) on the south side of the bridge over Mangatawai Stream, N112/250806.

Ngauruhoe Tephra 0·44 m Taupo Pumice 0·2 m

Mangatawai Tephra 0·8 m

Whakaipo Tephra & 0 ·24m Waimihia Lapilli

Papakai Tephra 0 ·24m

Poutu Lapilli 0 · 54 m 1m

Te Rato Lapilli 40 mm

Papanetu Tephra-Kara-piti Lapilli

?Rotorua Ash

?Puketarata Ash

1·9 m 0--40 mm

O·'i3 m

0·19 m l·4m 0·46m 0·63 m 0·9 +m

very dark grey ash to dark brown fine ash

(in pockets) pale yellow rhyolitic ash, lapilli and blocks

dark brown fine ash giving way to dark grey ash with interbedded very dark grey ash containing yellow leaves

dark yellowish brown ash with pale yellow rhyolitic lapilli, giving way to coarse yellow­ish brown rhyolitic ash

yellowish brown fine ash with interspersed grey and strong brown stained lapilli; buried soil

strong brown weakly shower-bedded lapilli andesitic tephra

olive grey lapilli

trace light yellowish brown fine ash

andesitic tephra pale yellow rhyolitic ash in yellowish brown

ash andesitic tephra

(pocket) fine white rhyolitic ash andesitic tephra alluvium andesitic tephra alluvium

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 TOPPING & KOHN- RHYOLITIC TEPHRAS AT ToNGARIRO 393

Access 10: a large cutting on the crest of a hill 2·5 km from the Waiouru-Turangi Road (Desert Road) on Hydro Access Road No. 10, N112/301844.

Ngauruhoe Tephra Taupo Pumice Mangatawai Tephra Whakaipo Tephra &

Waimihia Lapilli Papakai Tephra Poutu Lapilli

Poronui Tephra

Te Rato Lapilli

Papanetu Tephra-Kara· piti Lapilli

?Rotorua Ash

Rotoaira Lapilli

50+mm 0·6m 0·43 m 0·58 m

0·4m 0·36 m

40mm lOmm 0·44m

10mm 50mm

0-20 mm

1·3 m 20-30 mm 1·2 m 0·27m

1·1 m 4·5 m 1·4 + m

fine black ash pale yellow rhyolitic ash, lapilli and blocks dark yellowish brown to black ash fine yellowish brown ash with interspersed

pale yellow rhyolitic ash dark brown fine ash; paleosol (erosion break) yellowish red stained lapilli grey to yellowish brown ash fine yellow rhyolitic ash andesitic tephra grey coarse ash yellowish brown ash light yellowish brown rhyolitic ash

andesitic tephra fine pale yellow rhyolitic ash andesitic tephra 0 · 12 m strong brown pumiceous lapilli; 20 mm very dark grey fine ash grading into 80 mm strong brown and black coarse ash; 20 mm very dark grey ash grading into 30 mm olive yellow lapilli and ash andesitic tephra alluvium or laharic debris, on purplish grey igmmbrite; planar upper surface

Poutu: a large cutting on the National Park-Taupo Road, 5 · 7 km west of Rangipo, N112/239901. Type section for Poutu Lapilli and Rotoaira Lapilli.

Taupo Pumice Mangatawai Tephra

Whakaipo Tephra & Waimihia Lapilli

Papakai Tephra

Hinemaiaia Ash

Poutu Lapilli

Poronui Tephra

Te Rato Lapilli

?Rotorua Ash

Rotoaira Lapilli

Rerewhakaaitu Ash

0.40 m 0·42 m

0·3m

0·4m

0-30 mm

0·90m 60mm 20-30 mm 0·12 m 0·16 m

0·64m 0-20 mm

0·71 m 0·38 m

0·12 m

80mm

pale yellow rhyolitic ash, lapilli and blocks dark yellowish brown ash becoming dark grey

over bottom 0 · 2 m yellowish brown fine ash with interspersed

pale yellow rhyolitic ash strong brown ash with grey lithic lapilli

throughout; paleosol "cream cakes" of pale yellow brown rhyolitic

tephra occur in lower half of this unit brownish yellow wealrly bedded lapilli very dark greyish brown to dark olive grey ash pale yellow rhyolitic ash andesitic tephra very dark grey coarse ash and la!Jilli and pale

yellow lapilli andesitic tephra fine yellow rhyolitic ash, usually as "cream

cakes" about 20 mm across andesitic tephra 0·16 m yellowish red coarse ash and lapilli;

20mm (10-50mm) black ash; 0·2m shower bedded brownish laoilli and coarse ash (erosion) -

yellowish brown ash with scattered strong brown lapilli

light olive brown ash (sandy silt) with sparse strong brown lapilli; a few angular cobbles throughout these two units which are probably water·laid. In places up to 50 mm white rhyolitic ash present; may not be primary

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

394 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 16

0·38 m

Hinuera Formation 0·82 m

Oruanui Formation 0·39 m

0·57 m

2 + m

shower-bedded strong brown and brownish yellow ash and lapilli

current beddd gravelly sands (erosion) pale brownish grey massive ash with scattered

pumice lapilli (Oruanui Breccia) 0 · 31 m very pale brown ash, shower bedded

and studded with chalazoidites up to 30 mm across ; 40 mm pale yellow shower bedded ash; 0 · 12 m pale yellow shower bedded fine and coarse ash (Oruanui Ash); sharp con­tact with tuff, la9illi tuff and alluvium

Te Ponanga Saddle: a cutting on the eastern side of Te Ponanga Saddle Road near the summit, and to the north of Lake Rotopounamu, N112/224983. Type section for Papanetu Tephra.

Ngauruhoe Tephra Taupo Pumice Mangatawai Tephra Waimihia Lapilli Papakai Tephra

Poutu Lapilli

Poronui Tephra

Te Rata Lapilli

Papanetu Tephra

?Puketarata Ash

Unnamed rhyolitic ash

Rotoaira Lapilli

Rerewhakaaitu Ash

Oruanui Ash

0·15 m 0·95 m 0·34m 0·13 m 0·43 m

0·65 m

60mm

0·3 m

20mm 0-20 mm

0·85 m

30mm 0·16 m

20mm 0·12 m

85 mm

0·30m 60mm 0·60m

0·30m

1·5 + m

dark brown grey fine ash pale yellow rhyolitic ash, lapilli and blocks dark brown grey ash pale yellow rhyolitic ash yellow brown fine ash with interspersed grey

and strong brown lapilli; paleosol grey and strong brown coarse ash and lapilli (erosion) grey ash with a trace of light yellowish brown

fine rhyolitic ash dark gre"nish grey lapilli and coarse ash and

pale yellow lapilli yellowish brown ash. and coarse grey lithic ash pale yellow ash with coarse clear obsidian

and grey lithic ash andesitic tephra ( ?Rotorua Ash in other Te Ponanga Road

sections is about halfway down these units) isolated pocket of yellow rhyolitic ash yellowish brown ash isolated pocket of yellow rhyolitic ash yellowish brown ash 20 mm yellowish red coarse ash and lapilli;

S mm dark grey ash; 60 mm coarse strong brown ash and lapilli

yellowish brown ash white fine rhyolitic ash slightly gravelly sand, yellowish brown silts

with minor cobbles and boulders shower bedded pale brown ash, coarse ash

and chalazoidites · · alluvium; angular andesitic boulders and

cobbles in pale brown to grey brown silty matrix

Wairoa: a cutting 450 m east of C Wairoa Trig and 90 m west of Hydro Access Road No. 4 N112/105987.

Taupo Pumice Mangatawai Tephra Papakai Tephra

0·5 m 0·22 m 0·37 m

(variable) pale yellow ash, lapilli and blocks dark brown grey ash yellowish brown fine ash with sparse lapilli;

buried soil (erosion)

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4

No. 3 ToPPING & KoHN- RHYOLITIC TEPHRAS AT ToNGARIRO 395

Poutu Lapilli

Te Rato Lapilli

0·58 m 0·11 m 0·14 m

30mm

0·14 m 50mm 80mm

0·15 m

strong brown lapilli andesitic tephra greenish grey lapilli and ash yellowish brown ash and sparse coarse grey

lithic ash yellowish brown fine and coarse ash strong brown coarse ash and lapilli strong brown ash with interspersed coarse

ash and lapilli yellowish brown ash and sparse lapilli scattered

charcoal (NZ 1187, Table 2)

( ?Rotorua Ash is present as ··cream cakes" in this position in nearby sections, e.g., N112/096989).

0·13 m

0·25 m

20mm 0·25 m 0·1 m

0·6+m

yellowish brown ash with interspersed yellow­ish red lapilli

yellowish brown ash; charcoal (NZ 1186, Table 2) scattered over top 80 mm

yellowish red pumiceous and lithic lapilli brown to yellow brown ash yellowish brown ash with interspersed strong

brown pumiceous and dark grey to black lithic lapilli

yellowish browu loess and/ or tephra

Dow

nloa

ded

by [

Uni

wer

syte

t War

szaw

ski]

at 0

5:45

18

Oct

ober

201

4