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Massey Uniw· .. �i�v l -� ';·r-ry

New Zealand & Pacific Collection

SO I LS OF ELTHAM COUNTY

AND TH E

TEPHROCHRONOLOGY

O F

C ENTRAL TARANAKI

A thes i s p resented i n parti a l fu l fi l ment

of t he req ui rements for the degree of

Doctor of Ph i l osophy i n So i l S c i ence

at Mas sey Uni vers i ty

by

A L I SON MARGARET FRANKS

1984

...• , •.

Fronti s p i e ce . V i ew a cros s the s outh o f E l tham Co unty , to the north -wes t , wi th Mt . Egmont i n the background , from T i ri moana Road , a t Nl29/917395 . The l andscape s hown here compri ses an up l i fted mari ne bench ( Ka i a tea Te rrace ) overl a i n by l a hari c brecc i a ( E l tham Lah a rs ) and th i ck vol can i c a s h . So i l s a re mapped as Stratford hill-Stratford association.

ABSTRACT

The s o i l s o f El tham Co unty wes t of the Patea Ri ver , a re descr i bed

and the i r d i s tri but i o n s hown on a map at a s ca l e o f 1 : 50 , 00 0 . The s o i l ­

formi ng fac tors a re d i scussed w i th part i c ul a r emphas i s on t he so i l parent

1 materi a l s , w h i c h range from vol ca n i c a s h i n the west , to peat and

s ed imenta ry roc k , ma i nl y s i l t stone and s ands tone , i n the ea s t . An account

i s g i ven of the g enes i s and h i s tori ca l deve l opment o f the Ngaere and

El tham Swamps and a c l as s i fi cat i on made of the E l tham pea t .

A deta i l ed account i s g i ven o f the s trat i gra phy of the l ate Quaternary

teph ras i n centra l Taranak i . E i gh t n ew tephra un i ts (p2 , p l , E5 , E4 , E3 ,

E2 , E l a nd Ma hoe ) a re des cri bed , w i th type secti ons and reference l oca l i t i es

des i gnated . I sopach maps of thei r d i s tri but i on a re presented and an

attempt i s made to correl ate these tephras w i th those further north .

Deta i l s a re g i ven o f the westernmo s t occ urrences of Aokautere Ash and the

imp l i ca t i on s o f these for the Late Q ua ternary i n Taranak i a re exami ned .

Petrograph i c s tud i es , X- ray fl uores cence and chemi ca l ana l ys i s o f

ti tanomagneti tes by i n ducti ve ly-coup l ed a rgon p l asma emi s s i on spe-ctros copy

( I . C . P . ) a re a l so a pp l i ed to effect pos i ti ve i denti fi cati o n and corre l ati on

of the tephra s . The compo s i t i on o f the l i th i c Ma ngan u i tephra i s

es tabl i s hed as basa l ti c . .

The morphol o gy and phys i ca l p ro pert i es of the so i l s a re des cr i bed as

are the s o i l mapp i ng un i ts empl oyed i n th i s s u rvey . Characteri s t i cs of

the component members of the mapp i ng un i ts a re g i ven i n a n extended l egen d .

Fi fteen s o i l taxonomi c un i ts have been recogn i s ed a n d named i n the s o i l

s urvey . Des cr i p t i ons des i gned pri mar i l y for corre l ati o n and reference

purpo s es a re prov i ded for each of the taxonomi c un i ts . The s o i l s a re

i i

a l s o rated i n terms of thei r l i m i ta t i ons for pas tora l c ro pp i ng , hort i c u l tural ,

forestry and u rban uses and i n terms of thei r va l ue for food product i o n .

The pos i t i on o f the boundary between S tratford and Egmont so i l s i s

es tab l i s hed and a bas i s for d i s t i n g u i s h i ng the two s o i l s i s proposed .

By exami n i ng two s teep l and s ubcatchments i n deta i l a n i ns i ght i s provi ded

i n to the w i de range of vari ab i l i ty found i n the s teep l and so i l s i n the

eas t of E l tham Co unty . An i nd i cat i o n o f the presence o f vol c an i c ash or

i ts ab sence due to ero s i o n i s g a i ned by a pp ly i ng the phos phate retent i on

and a l l o phane tes t . Th i s a l so pro vi des a n unders tandi ng o f the pattern

of paren ta l materi a l vari ab i l i ty .

Fi na l l y , s el ected l a boratory ana l ys es h ave been c ho s en to hel p

c haracteri se the chemi c a l a n d phys i ca l properti es o f fi ve yel l ow-brown

l oams , a g l ey , an i n tergrade between yel l ow-brown l oams and recent s o i l s

a nd an organ i c so i l from E l tham Coun ty . Deta i l ed a na lyti ca l data from

ten New Zeal a n d So i l B ureau reference s i tes i n Taranaki a re i nc l uded for

comparat i ve p urposes .

i i i

i v

AC KNOWLEDGEMENTS

I wou l d l i ke to thank my s upervi sors D r . V . E . N ea l l a nd Dr . J . A . Po l l ok .

D r . Neal l •s pati ent g u i dance a nd Dr . Po l l o k•s enthus i asm were much

apprec i a ted .

I am grateful to my co l l eag ues Mr . R . C . Wa l l ace , and Dr . R . B . S tewart ,

who prov i ded he l pful a dvi ce and construct i ve cr i ti c i sm . Thanks a re a l so

due to Mr . J . H un t , S o i l B u rea u , D . S . I . R . Wel l i ng ton , for a s s i s tance wi th

the X -ray fl uore s cence, to Dr. J . Lee , Appl i ed B i ochemi s try D i v i s i on ,

D . S . I . R . Pa l merston Northf

for I CP ana l ys es o f the t i tanomagneti te sa.nd +o f\lQ),-i zw.\t,�.nO. Soi I Bu.re.a.\A 1or +he. ve�r£.nce s·rte CA.nctl;iS"es.

Acknowl edgemen t i s g i ven to New Zea l a nd So i l B u rea u , Depa rtment o f

Sc i ent i f i c a nd I nd u s tr i a l Research , for fund i ng t h e proj ect 1 1 So i l a nd

As hbeds i n Taranak i 1 1 • I n parti cu l ar s pec i a l recogn i t i on i s g i ven to

Mr. R . H . W i l de a nd Mr . J . D . Cow i e of New Zea l and So i l Bureau for fi e l d

corre l at i on and encouragement .

I must a l s o thank Mrs . D . Syers for h er effi c i ent typ i ng a nd

Mr . M . R . Lew i s for data ana l ys i s .

Fi n a l l y , I o ffer gra teful th anks to Ms . S . L . Marx and other fri ends ,

i n both Taranak i a nd Pa l mers ton North , and my fami l y , who h ave been

support i ve thro ugh o u t .

FRONT I S P I ECE

ABSTRACT . .

ACKNOWLEDGEMENTS

TABLE OF CONTENTS

L I ST OF F I GURES

L I ST OF TABL ES

L I ST OF PLATES

TABLE OF CONTENTS

CHAPTER 1 . I n troducti on

1 .

2 .

Prev i o us Work

Genera l Des cr i pti on of Area

CHAPTER 2 . So i l formi ng env i ronmen t o f E l tham Co unty

1 . Phys i ogra phy

2 . Vegetati on

3 . C l i mate . . .

4 . So i l Parent Materi a l s

i . Reg i ona l Quaternary H i s tory . . . . i i . Quate rnary H i s tory o f E l tham County

5 . Drai nage and I ron Movemen t

6 . Genes i s a n d H i s to ri ca l Devel o pment o f the Ngaere and E l tham Swamps .

CHAPTER 3 . Teph roch rono l ogy o f Central Taranak i

1 . I ntroduct i on . . . . . .

2 . Defi n i t i ons a nd Termi no l ogy .

.

3 . H i s tori ca l Background and P revi o us Work

4 . Method of S tudy . .

5 . Stra t i g raph i c Un i ts .

.

Page

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V

vi i i

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x i v

1

6

10

1 1

1 5

2 3 24

34

37

5 1

5 3

5 5

58

6 1

V

CHAPTER 3 .

6 . Systemat i cs

i . Late Quaternary Tephras o f Cen tra l Tarana k i .

i i . The Wes ternmos t Occu rren ces o f Aoka utere As h and Imp l i ca t i ons for the Late Quaternary i n Taranak i . . . . . . . . . . . . . .

CHAPTER 4 . Mi nera l og i cal I denti fi cat i on of Centra l Tarana ki Teph ras

1 .

2 .

3 .

4 .

P rev i o us work .

X- Ray Fl uores cence Spectrometry

Chemi ca l Ana l yses of T i tanomagneti tes from Taranak i Tephras . . . . .

Mi n era l ogy o f the Tep h ra Seq uence

CHAPTER 5 . So i l s o f El th am County

1 . S o i 1 Mapp i n g and Taxonomi c Un i ts

2 . S o i 1 Gro ups i n S urvey Area

3 . So i l Taxonomi c Un i ts . .

4 . S o i l Mappi n g Un i ts . .

5 . D i s t i ng ui s h i ng Stratfo rd So i l s from Egmont

6 . An I ns i gh t i n to the Vari a b i l i ty of the Steep l and So i l s . . .

CHAPTER 6 . L abo ra tory Analyses

S o i l s a nd Sampl i ng S i tes .

Resul ts . . . .

pH Mea s urements

Organi c Matter . .

Phospho rus . . .

Cati o n Exch�nge Properties

Reserve Pota s s i um and Mag nes i um

Su l ph ur . . . . . .

. . . .

So i l s

.

1 .

2 .

3 .

4 .

5 .

6 .

7 .

8 .

9 . Aci d-Oxal a te Extrac tab l e I ro n , Al umi n i um and S i l i con .

1 0 .

1 1 .

1 2 .

1 3 .

B u l k Dens i ty . . . . . .

Mo i sture Retenti on . . .

Al l o phane and Tota l C l ay

Conc l us i on . . . . . . .

v i

Page

6 2

85

9 1

92

97

103

1 15

1 23

1 25

146

1 5 5

1 84

2 1 9

224

232

2 34

2 36

24 1

249

249

255

26 1

264

2 6 7

267

CHAPTER 7 .

REFERENCES

APPEND I CES

Cone 1 u s i ons . . . . . . . . . . . . . . . . . . . . . . .

I .

I I .

I l l .

I V .

V .

V I .

V I I .

L i s t of Strati graph i c Sect i ons Men ti oned i n Text . . . .

Aoka utere As h Local i ti es

Deta i l ed Descri pti ons of Two Refe rence Local i ti es

Extended Legend

So i l L i mi tat i ons for Use

So i 1 Taxonomi c Uni t Sheets

Sma l l S ea 1 e Maps . .

So i l Map i ns i de back cove r .

Page

2 7 3

2 76

287

289

29 1

305

3 19

332

4 1 1

v i i

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1 . 1

1 . 2

2 . 1

2 . 2

2 . 3

2 . 4

2 . 5

2 . 6

3 . 1

3 . 2

3 . 3

3 . 4

3 . 5

3 . 6

3 . 7

3 . 8

3 . 9

3 . 10

3 . 1 1

3 . 1 2

3� 1 3

3 . 14

L I ST OF F I G URES

Locati on of El tham County . . .

Pr i nci pa l s t reams and ri vers i n E l tham County

Mean annua l ra i nfa l l i s ohyets , Ta ra n a k i reg i on ( Offi c i a l New Zeal and , Meteoro l og i ca l Offi ce data 194 1 - 1 9 70 ) . . . . . . . . . . . .

Quaternary geo l og i ca l map of E l tham County

Locati on o f the Ngaere and El tham Swamps

Ngaere sect i on survey map ( 189 5 )

Contour map o f Ngaere and E l tham Swamps a t 100 1 i n terva l s . . . . . . . . . .

P rofi l e o f E l tham peat nea r Rawh i t i roa Road

D i stri but i on of we l l dra i ned s o i l s o f central and s outhern Tarana k i as governed by the di s tri but i on of tephra . . . . . . . . . .

Loca l i ty map of Taranak i s howi ng s tudy a rea

Strati graph i c secti ons refe rred to i n text ( for l oca l i ty detai l s see Append i x I )

I sopach map of un i t p2

Appearance of uni t E5 .

I s opach maps of uni t E5

Appea rance of un i t E4 .

I sopach map s of un i t E4

Corre l a t i on co l umns 1 - 8 from near I n g l ewood to Type Sect i o n , Mangatok i S tream . . . . .

Appeara n ce o f un i t E3

I s opa c h map o f un i t E3

Appea rance o f un i t E2

Appeara n ce o f uni t E l

Appearance o f the Mahoe tephra

Page

7

8

1 7

2 6

38

40

42

48

59

60

60

65

67

69

7 1

7 3

74

76

7 7

80

8 2

84

v i i i

Fi gure

3 . 1 5

3 . 16

4 . 1

4 . 2

4 . 3

4 . 4

4 . 5

4 . 6

4 . 7

5 . 1

5 . 2

Th i ckness ( i n mm ) and i so pach s for Aokautere As h i n central and s outhern Tarana k i .

I s opachs ( a t 1m i nterva l s ) o f tephri c materi a l s post-20 , 000 years B . P . i n Taranak i . . . . . .

C l as s i fi cati on of rocks 1 1 typi cal l y a s s oc i ated w i th andes i te s i n orogen i c a reas 1 1 ( after Tay l o r , S . R . , 1969 , p 45 ) . . . . . . . .

Pa rkers I n dex versus % K20 fo r the tephra s equence . . . . . .

Graph of manganese va l ues versus z i n c va l ues for the Taranak i teph ras

P rofi l e of E l tham peat from El tham Swamp

Sec t i on exposed i n upper part of d ra i nage d i tch , Durham Road . . . . . . . . .

D i agram to s how ra nge o f aug i te va l ues i n the teph ra s equen ce , Kaupokonui - p 1

D i agram to s how range o f augi te va l ues i n pre - p l tephras . . . . . .

Hypothet i ca l c ros s - sect ion of E l tham County s howi ng s o i l s eri es i n rel at i on to l ea ch i n g , dra i nage and parent materi a l s . . . . .

Grange and Tayl or ' s reconna i s s ance s o i l map of wes tern Taranak i mod i fi ed to s how d i s tri but i on o f Egmo n t and Stra tfo rd s oil s e ri es i n v i ci n i ty of s tudy a rea . . . . . .

5 . 3 Modi fi ed s o i l map of part of Taranak i i n

Page

88

90

95

96

1 02

106

1 07

1 1 1

1 12

1 22

1 56

v i c i n i ty o f s tudy area by N . Z . S o i l Bureau , 1 9 54 . . . . . 1 57

5 . 4

5 . 5

5 . 6

5 . 7

5 . 8

Map to s how present k nown d i s tri but i o n of Stratford and Egmo n t soi l s i n vi c i n i ty o f s tudy a rea . . . . . . . . . . . . . .

S ampl i ng s i tes o f a Patua s o i l , Burre l l s o i l , four S tra t fo rd s o i l s , a S tratford fi ne topso i l vari ant and three Egmont s o i l s . . . . . .

E l eva t i on versus pHH 2o a t�� and 1m depth

Fl ow d i a gram to a i d f i e l d i denti fi cati on of Stratford s e ri es , S tratfo rd s eri es f i ne topso i l vari a n t and Egmont s eri es . . .

Locati on o f s teep l and a reas i n central E l tham County

1 62

1 7 1

1 74

183

185

i x

Fi gure

5 . 9

6 . 1

6 . 2

6 . 3

6 . 4

6 . 5

6 . 6

6 . 7

6 . 8

6 . 9

6 . 10

6 . 1 1

6 . 1 2

6 . 1 3

6 . 14

6 . 15

6 . 16

Locat i o n of s teep l and s tudy areas

Locat i on of s o i l s i te i nformat i on referred to i n s o i l ana l ys es sect i o n . . . . . . .

Va l ues fo r pHH 0 and pHNaF i n the s o i l toposequefice of th i s s tudy . .

Va l ues for pHH2o and pH NaF i n the s o i l c l i moseque nce of th i s s tudy

0 . 5M H 2 S04 extractab l e p ho s phorus val ues i n the s oTl Cl i mos equence of th i s s tudy . .

Phosphate retent i on val ues i n the s o i l c l i mosequence o f th i s s tudy for s i x s e l ected Tarana k i s o i l s . . . . .

. ( I Bases ) B a se saturat1on CEC pH 7 NH40Ac i n the s o i l c l i moseque nce . . . .

Reserve pota s s i um val ues for ni ne Ta ranak i s o i l s

Reserve magne s i um va l ues for n i ne Tarana k i s o i l s

Phos phate-extractab l e sul phate versus phos phate retent i on for s eventeen s el e cted Taranaki s o i l s

Phos ph ate-extractab l e sul ph ate val ue s i n a s o i l toposequence of th i s s tudy . . .

Phosphate-extractab l e s ul ph ate val ues i n the s o i l c l i moseqeunce of th i s s tudy

Aci d-oxa l a te extractab l e a l umi n i um va l ues i n a s o i l toposequence of th i s s tudy

Aci d-oxa l a te extractabl e i ron i n the s o i l c l i mosequence and toposequence of th i s s tudy

Ac i d-oxa l a te extractab l e i ron versus phos ph ate retent i on for seventeen s e l e cted Taranak i so i l s

Bul k dens i ty and tota l poros i ty o f s i x se l ected Tarana k i s o i l s . . . .

H i s tograms to s how rel a ti ve amounts o f Total C l ay a n d A l l ophane i n fi fteen Taranak i s o i l s

Page

185

223

233

233

240

242

245

250

2 50

252

2 54

2 54

256

257

2 60

262

268

X

Tab l e

1 . 1

2 . 1

2 . 2

2 . 3

2 . 4

2 . 5

2 . 6

3 . 1

3 . 2

4 . 1

4 . 2

L I ST OF TABLES

Correl a t i on of s o i l s eri es i n th i s survey wi th s o i 1 sets of "Genera 1 survey of the s o i l s of N orth I s l and , New Zea l a nd " ( N . Z . So i l Bureau , 1 9 54 ) and un i ts o f other so i l surveys i n Taranak i

Month l y and annual ra i nfa l l fi gures for R i verl ea between 19 13- 1980 ( i n mm) . Suppl i ed by N . Z . Meteoro l ogi ca l Servi ce

N . Z . Meteoro l og i ca l Serv i ce ra i nfa l l norma l s for El tham and Omoana 1 94 1- 1970 ( i n mm ) from N . Z . Meteorol og i cal Servi ce M i s e . Pub . 145

N . Z . Meteoro l og i ca l Serv i ce summari es of c l i matol og i ca l observat i ons to 1980 for S tra tford Demon strati on Farm . . . . . .

N . Z . Meteoro l og i ca l Serv i ce summari es o f c l i mato l og i c a l observati ons to 1 980 for S tratford Moun ta i n House . . . . . . . .

Rel a t i ons h i ps between South Tarana k i mar i ne terraces and vol can i c act i v i ty i n wes tern Tarana k i a s a dopted i n th i s survey ( Adapted from P i l l ans , 198 1 ) . . . . .

Bul k dens i ty va l ues for the El tham peat

C h ronol ogy and d i s tri buti on of pri n c i pa l Quaternary vo l can i c depos i ts i n centra l and eas tern Taranak i . . . . . . . . . .

Granul ometri c c l a s s i fi cat i on of pyro c l a s ts a nd o f un i moda l we l l sorted pyrocl ast i c depos i ts

Major e l ement ana lyses by X- ray fl uorescence o f a teph ra s equence i n Tarana k i . . . .

Chemi ca l a n a l yses of t i tanomagneti tes from Tarana k i tephra s . . . .

4 . 3 Percentage augi te , hornb l ende and hypers thene

Page

5

1 8

1 9

2 1

22

25

49

52

54

9 3

98

i n the tephra s equence . . . . . . . . . . . . . . . . 1 04

4 . 4 Rat i os of ferromagnes i an mi nera l s i n the teph ra s equence . . . . . . .

4 . 5 Rati os of ferromagnes i an mi nera l s i n teph ra

. . . . . . . . 109

s amp 1 es from E l tham Swamp a nd Durham Road . . . . . . . . . 1 10

x i

Tab l e

5 . 1

5 . 2

5 . 3

5 . 4

5 . 5

5 . 6

5 . 7

5 . 8

5 . 9

5 . 10

5 . 1 1

5 . 12

5 . 1 3

5 . 14

6 . 1

6 . 2

6 . 3

6 . 4

6 . 5

6 . 6

6 . 7

So i l mapp i ng u n i ts a rranged phys i ograph i ca l l y

S o i l taxonomi c un i ts a rranged pedo l og i ca l l y

So i l members w i th i n a s soc i at i ons a n d the i r re l at i on to topog ra ph i ca l s i tes . . . . . .

Teph ras c urrent ly recogn i s ed i n E l tham county

Range of e l eva t i o n a nd ra i nfa l l , l a ndform and mean annua l a i r temperature under wh i ch S tra tford , S t ra tford fi ne topso i l vari a n t and Egmont so i l s a re found . . . . . . . . . .

Range of general morpho l ogi ca l profi l e features

pHKCl and pHH2o res u l ts

pHNaF res u l ts .

Phos phate retenti on res u l ts

% Decreas e of 15-bar water res u l ts

We i ghted average 15- bar moi s ture retent i on - fi e l d mo i s t a nd a i r dry . . . .

KC l -extracta b l e a l umi n i um res u l ts . . . .

N . Z . Meteoro l og i cal Servi ce s ummari es of c l i ma to l ogi ca l observat i ons to 1980 for Te Wera Forest . . . . . . .

A l l ophane test and p hos phate retenti on va l ues for Area 1 and Area 2 . . . . . . . . . . . .

Deta i l s of the e i g h teen so i l s i tes i n Taranak i

Res ul ts of chem i c a l a nd phys i ca l a na l yses of s el ected Taranak i s o i l s . . . . .

Rat i ngs for chemi ca l properti es . .

D i a gnos ti c p roperti es of 1 1Amo rphous mater i a l domi nant i n the exchange compl ex 1 1 • • • • • •

Organ i c matter ( % Organ i c C x 1 . 7 ) i n seventeen Taranaki s o i l s . . . .

I norgan i c phos phorus fracti on s o l ub l e i n 0 . 5H2S04 as a percentage of i norgan i c phosphorus i n s eventeen Tarana k i s o i l s

E ffecti ve base s a tu rat i on of e i g h teen s o i l s from Taranaki . . . . . . . . . .

Page

1 16

1 1 8

1 21

1 60

1 64

168

1 7 3

1 7 5

1 7 6

1 78

1 7 9

1 8 1

1 94

2 16

220

225

2 29

2 3 1

2 35

2 39

244

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Tab l e

6 . 8

6 . 9

6 . 10

6 . 1 1

6 . 1 2

Exchangeab l e a l umi n i um as a percentage of ECEC of s eve n teen s o i l s from Taranak i

Correl a ti on matri x between a l l vari ab l es

Rati o between sod i um pyrophos phate extractabl e a l umi n i um and i ron and c i trate-d i th i on i te a l umi n i um and i ron . . . . . .

1 5-bar water content for seven teen s o i l s i n Taranak i . . . . . . . .

C l as s i fi cat i on of s o i l s from Taranak i a ccord i ng to So i l Taxonomy and the 1978 Andi so l Proposa l . . . . . . . . . . . .

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2 5 3

259

2 66

2 7 2

P l ate

Front i s p i ece

2 . 1

2 . 2

2 . 3

2 . 4

2 . 5

2 . 6

2 . 7

2 . 8

2 . 9

2 . 10

2 . 1 1

2 . 12

3 . 1

3 . 2

3 . 3

3 . 4

L I ST O F P LATES

Vi ew acros s the so u th of E l tham Cou n ty , to the north -wes t , w i th Mt . Egmon t i n the �ack g round , from T i �moana Road . .

V i ew of Managami n g i d i stri c t , l ook i ng north-west , above Mangami ng i S tream .

V i ew of Mangami n g i d i s tr i c t . S tratford Formati on i n the foreground .

Look i ng north-we s t between Mounta i n Roa d a n d Boyl an Road . E l tham Lahars i n the foreground . . . . . . . . . . . . . .

V i ew of Mangami n g i d i s tri c t , l oo k i n g wes t . P atea R i ver i n the foregro und wi th Opunake terrace and S tratford terrace above . . . . . .

Pungare h u Format i o n , near Lower S tuart Road

Mt . E gmont . Lah a r mounds o f the Warea Forma ti on .

Warea Lahar exposed on Upper Auroa Road

Opua Lahar exposed on E l tham Road

Mangawhero s oi l , near R i verl ea

V i ew north of the Ngaere Swamp from Rawhi ti roa Road . . . . . . . . . .

Expos ed roots of a Dacrycarpus dacrydi o i des ( Kah i k a tea ) . . . . . . . . . . . . . . . .

Sect i on exposed i n d i tch s howi ng B urre l l l a p i l l i , Kaupokonu i tephra , Maketawa tephra , a n d Manganu i tephra . . . . . . . . . . . . .

Sect i on exposed on Opunake Road , 0 . 6 km from Mahoe . Type sect i o n for p2B , p2A and p1 . . . . . . . . . . .

Deta i l o f tephras p2A and p 1 ( Kor i to teph ra ) Secti on expose d near Tari k i . . . . . . . . .

Deta i l of s ect i on exposed a t Mahoe , on Opunake Roa d . . . . . . . . . .

V i ew of sect i on exposed on Opunake Road , a djacent to Mangatok i S tream . Type s ec t i on for E4 tephra . . . . . . . . . .

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1 2

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29

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32

3 2

3 3

35

39

39

4 7

6 4

64

67

70

x i v

Pl a te

3 . 5

3 . 6

3 . 7

3 . 8

3 . 9

3 . 10

3 . 1 1

5 . 1

5 . 2

5 . 3

5 . 4

5 . 5

5 . 6

5 . 7

5 . 8

5 . 9

5 . 10

5 . 1 1

5 . 1 2

5 . 1 3

5 . 14

5 . 1 5

Deta i l o f E 4 teph ra a t Wa i ngongoro Road

Deta i l o f E 3 teph ra on Pembroke Roa d , 1 . 5km s o uth from Barc l ay Roa d . .

V i ew of s e c t i on exposed on Pembroke Roa d , 1 . 5km s outh from Barc l ay Roa d . Reference l ocal i ty for E2 . . . .

Deta i l o f E 2 a t the type s ect i o n , on Opuna ke Road , above the Wa i ngongoro Stream

Reference l ocal i ty for the Mahoe tephra , on Opunake Road , 0 . 6 km from Card i ff

Secti o n exposed on Ti ri moana Road s howi ng the Oma h i na Tephra i n terbedde d i n a ndes i tic ashes

Sect i on a djacent to Opunake Road , n ear Rona l d Roa d s how i n g the Aoka utere As h

Rowan s o i l , Uppe r Mangawhero Road

Rowan s o i l near Uppe r Mangawhero Road

Ri verl e a s o i l , near E l tham Road . .

Ma kaka s o i l a t the type secti on , near Upper Mangawhero Road . . . . .

Lowga rth s o i l , a t the type s ect i on , near Lower Has ti ngs Road

Kah u i so i l core , near Ri verl ea

Ti poka s o i l , near Auroa Road

Ha ngata h u a so i l , near Mana i a Roa d

S tratford so i l , near Lower H a st i ngs Road

Stratford fi ne tops o i l vari a n t on H i c ks Road

Egmont s oi l , 1 km wes t of Mokoi a , a l ong mai n Wangan u i -Hawera h i g hway

S tee p l a n d s tu dy Area 1 .

S teep l a n d s t udy Area 2 .

Expo s u re of moderatel y consol i da ted s i l ty s ands tone be l ong i ng to the Matemateonga Formati o n at Mangami ng i Sadd l e . . . . .

V i ew from s tudy Area 1 l ook i ng south-ea s t

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89

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XV

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P l a te Page

5 . 1 6 Ri dge profi l e Area 1 . . . . . . . . . 200

5 . 1 7 I ntermed i a te steep s l ope profi l e , Area 1 202

5 . 1 8 I ntermed i a te s teep s l ope pro fi l e , Area 2 . 202

5 . 19 Eroded s l ope s i te , Area 1 . . . . . . . 204

5 . 20 Profi l e from zone of l ocal accumul a t i o n at foot of eroded s i te . . 2 04

5.2 1 Accumul a t i on s l ope p rofi l e , Area 1 . 206

5 . 22 Eroded s l ope s i te , now s tab i l i sed 2 10

5 . 23 Eroded s l ope p rofi l e . 2 1 0

5 . 24 V i ew north of a cc umul a t i on s l ope s i te , Area 2 . . . 2 1 2

5 . 25 Acc umu l a t i on s l ope profi l e 2 1 2