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

A lower Cretaceousunconformity in easternWairarapaM. R. Johnston aa New Zealand Geological Survey, DSIR , NelsonPublished online: 02 Feb 2012.

To cite this article: M. R. Johnston (1974) A lower Cretaceous unconformity ineastern Wairarapa, New Zealand Journal of Geology and Geophysics, 17:1, 143-148

To link to this article: http://dx.doi.org/10.1080/00288306.1974.10428481

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No.1 143

A LOWER CRETACEOUS UNCONFORMITY IN EASTERN WAIRARAPA

M. R. JOHNSTON

New Zealand Geological Survey, DSIR, Nelson

(ReceitJed 14 March 1973)

ABSTRACT

Recent mapping in the Tinui-Awatoitoi district has revealed a major unconformity in what was previously considered to be a continuous Cretaceous sequence. The rocks below the unconformity, mapped as the Torlesse Supergroup, are strongly folded, indurated greywacke and argillite, locally containing Upper Jurassic (Upper Tithonian) fossils. Overlying the unconformity are less indurated gently folded sediments of Clarence and Raukumara Series (Albian-Campanian) age mapped as the Mangapurupuru Group. The occurrence of an unconformity at a comparable strati­graphic position elsewhere on the east coast of New Zealand is discussed.

INTRODUCTION

The write~ (in press) has mapped in detail the Tinui-Awatoitoi district (Sheet N159 and part Sheet N158, NZMS1) of the Wairarapa (Fig. 1) which Wellman (1959, p. 115) considered probably contained the best Cretaceous section in the Wairarapa. An area near Tinui was subs,equently mapped by Haskell (1964) who thought that the section was continuous from the basal Cretaceous. Neither Wellman or Haskell found any Lower Cretaceous fossils and recent mapping has shown that the sequence is not continuous.

UPPER MESOZOIC STRATIGRAPHY OF THE TINUI DISTRICT

In the Tinui-Awatoitoi district (Fig. 2) the Upper Mesozoic stratigraphy is divided into two units by a well-defined angular unconformity separating indurated and complexly folded rocks of the Torlesse Supergroup from overlying less indurated and gently folded rocks of the Mangapurupuru and Tinui Groups (Johnston in press).

The unconformity has been recognised at six localities:

Locality (see Fig. 2) 1. Northern tributary,

Makirikiri Stream 2. Target Stream 3. Southern tributary,

Makirikiri Stream 4. Hilltop west of

Whakarora Valley S. Mangapakeha Valley 6. Mangapokia Valley

Grid Reference* N159/490707

N15S/442765 N159/47<"!7H3

N159/478706

N159/450670 N158/420635

Fossil collections from the basal conglomerate N159/f616,f763t

N15H/f774-777

N15R;f456

*Grid references are based on the national thousand-yard grid of the 1:63 360· topographical map series.

tN.Z. Fossil record number.

N.Z. Journal of Geology and Geot1hysics 17 (1): 143-8

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144 N.Z. JoURNAL OF GEOLOGY AND GEOPHYSICS VoL. 17

WELLINGTON

Palmerston North

0 50 10° Kilometres

JQP 29° Miles

FIG. 1 - Map of souther'! part of the NPrth Island. showing limits of the Tinui-Awatoi­toi district.

The Toclesse Supergroup consists of greywacke-argillite beds, massive greywacke, minor conglomerate beds, minor spilitic lava, and rare limestone lenses. At one locality in the North Branch of Makirikiri Stream a boulder of limejtone, similar to the limestone in le'1ses in the supergroup, yielded Buchia cf. hochstetteri Fleming (Nl59 jf435). This indicates a Puaroan (latest Jurassic) age for much of the supe:group in the Tinui-Awatoitoi district. Sparse fossils at five localities in the supergroup in the Wairarapa, are all Upper Jurassic in age (G. R. Stevens pers. comm.).

Overlying the unconformity is a conglomerate, about 12-20 m thick, containing two types of pebbles in a sandstone or siltstone matrix. The dominant pebbles are subangular to sub-ounded and are lithologically similar to the rocks forming the Torlesse Supergroup. The remaining pebbles are hard, round, commonly highly polished, are smaller than the majority, and form less than 5% of the conglomerate. They comprise highly altered and silicified gr,eywacke, ignimb~ite, tuff, rhyolite, dacite, granite, and diorite (Johnston & Browne 1973).

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FIG. 2 - Geological sketch map of the Tinui - Awatoitoi district showing location of un­conformities men­tioned in the text.

35 55

35

t

I 01234km I I I I I

I i 0 1 2 miles

•I localities mentioned in text

-

Younger Rocks

Tinui Group Te Mai Fmn

Glenburn Fmn

Mangapurupuru { Springhill Fmn Group ·

Maringi Fmn

f;~~t(}:) ~~~=~:~up

75

65 75

~ .....

]' z ~ z I

i ~

Q t%l

~ (") t%l

g (JJ

~ 8 z >!j

~ ~

~

..... .,.. VI

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146

(/) ::J 0 w u < e­w

"' u

N.Z. JOURNAL OF GEOLOGY AND GEOPHYSICS VoL. 17

SERIES

w u z w

"' :5 u

STAGE

Ngaterian

Motu an

Urutawan

Korangan

- - +--------!

- - -+-------1 w

" w e­o

Puaroan

TINUI

N158 N159

Springhill Fmn

DANNEVIRKE (Lillie,1953)

Raukumara

Fmn

WESTERN RAUKUMARA

(Speden 1973)

Karekare

Siltstone Fmn

y

MARLBOROUGH ~ (Upper Awatere

River) (Chaii>S 1966)

< w >-

1--------1 100

Winterton Fmn

Manngt •••••••.••••• Fmn

Te Wera Sandstone Fmn

Gladstone

Fmn

Sandstone Fmn (Type

Korangan Stage}

... K~;;n·g~·... IT ?IT? 106

.illiil·l·il'lto 0 \9j 7 112

UpLiFT AND 1'.1 Torlesse Super_g{oup.

greywacke-argllltte beds, age larg1ely uncertatn but constderablyl more ttH.luyated and folded than the overlytng beis. I ;....;..;..;..; unconformtty

135

145

FIG. 3-Stratigraphic columns, east coast of New Zealand. N.B. The Western Raukumara column is based on Speden (in press) as well as Speden (1973).

The basal conglomerate commonly contains fossils but only at localities 2 and 6 are they sufficiently well preserved to be identified. At locality 2 th:oy are probably Motuan, possibly Urutawan (I. G. Speden pers. comm.), and at locality 6 they indicate a Motuan or Ngaterian age. At all localities the con3lomerate grades upwards into fossiliferous Motuan rocks. At localities 1, 2, and 3 the rocks are siltstones fo~ming part of the Maringi Formation (Fig. 3) and at localities 4, 5, and 6 the rocks are massive mudstones of the Springhill Formation. The unconformity in the Mangapokia Valley is of interest as it was first recognised by Ongley (1936) who considered that the conglomerate was the base of his Tinui "Series"*.

THE RELATIONSHIP BETWEEN CRETACEOUS AND JURASSIC SEDIMENTS IN

NEW ZEALAND

Wellman (1959) in his review of the Cretaceous of New Zealand, stated that "deposition may have been substantially continuous over parts of New Zealand from the Jurassic until the Cenozoic". He considered that there was no evidence of a major unconformity within or at the base of the Cretaceous. This has been accepted by many geologists, although local un-

*The Tinui "Series" has been redefined as Tinui Group (Upper Cretaceous) by Johnston (in press).

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No.1 JoHNSTON- LOWER CRETACEOUS UNCONFORMITY 147

conformities have been recognised and accepted. Some geologists, however, have maintained that a major unconformity exists in the Lower Cretaceous (e.g., Fleming 1962, 1970; Stevens 1965). They use as evidence the lack of lowermost (Neocomian) Cretaceous and uppermost Jurassic (Upper Tithonian) faunas indicating a gap in the fossil record of about 30 m.y.

A major angula:: unconformity exists in the Tinui-Awatoitoi district, between the Todesse Supergroup and the younger Mangapurupuru Group. The unconformity shows that folding, uplift and erosion probably took place mainly during Lower Cretaceous time and can be correlated with similar unconformities on the east coast of New Zealand (Fig. 3).

In the Dannevirke subdivision, Lillie ( 195 3) ,recognised that his Rauku· mara Formation of Clarence age, with basal conglomerate, unconformably overlies greywacke-argillite beds. He stated (p. 75) that "It [strong folding} probably preceded deposition of the Raukumara beds". Further north, Speden (1973 and in press) has shown that an unconformity, separating Jurassic rocks (belonging to the Torlesse Supergroup) from shelf sediments of Urutawan, and, locally Korangan age, exists over the western part of the Raukumara Peninsula.

In the Aorangi Mountains, south of the Tinui-Awatoitoi district, the Whatarangi Formation contains shallow-water fossils (Bates 1969) which are now considered to be Urutawan in age (I. G. Sped en pers. comm.). The formation is in fault contact with older indurated and crushed greywacke­argillite beds (Bates 1969). In Marlborough the upper Mesozoic succession has been considered to be largely continuous in the east (Wellman 1959, Lensen 1962, Hall 1963) but in the west there is a major unconformity (Suggate 1958, Challis 1966).

The distribution of the known unconformities indicates that at some time between the Puaroan (Early Tithonian) and Korangan (Aptian) stages, most of the present east coast kom western Marlborough to East Cape was elevated close to or above sea level.

Elsewhere in New Zealand there is a marked break between the youngest rocks deposited in the New Zealand Geosyncline (both marginal and axial fades) and the overlying less indurated rocks (Wellman 1959). The break may have formed contemporaneously with breccias (e.g., Hawks Crag Breccia) of Lower Cretaceous (Albian-Aptian) age in the. west and south of the South Island. G~anitic intrusions in North-west Nelson, dated as Lower Cretaceous in age (Aronson 1965, Hulston & McCabe 1972), may be associated with the break.

CoNCLUSIONS

The unconformity at the base of the Mangapurupuru Group in the Tinui­Awatoitoi district supports the concept of a period of uplift and erosion over much of the New Zealand area during the Lower Cretaceous.

ACKNOWLEDGMENTS

The writer is indebted to Drs I. G. Speden and R. P. Suggate, N.Z. Geological Survey, for constructive criticism of the manuscript.

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148 N.Z. JOURNAL OF GEOLOGY AND GEOPHYSICS VoL. 17

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BATES, T.

CHALLIS,

Geo{1hysics 8 (3): 401-23.

G. 1969: The Whatarangi Formation (Lower Cretaceous), Aorangi Range, Wairarapa, New Zealand. Transactions of the Royal Society of N.Z. (Geolon) 6: 139-42.

G. A. 1966: Cretaceous stratigraphy and structure of the Lookout area, Awatere Valley. Transactions of the Royal Society of N.Z. (Geology) 4: 119-37.

FLEMING, C. A. 1962: New Zealand biogeography-A paleontologist's approach. Tuatara 10 (2): 53-108.

1970: The Mesozoic of New Zealand: chapters in the history of the circum Pacific Mobile Belt. Quarterly journal of the Geological Society of Londoll 125: 125-70.

HALL, W. D. M. 1963: The Clarence Series at Cover ham, Clarence Valley. N.Z. journal of Geology and Geophysics 6 (1): 28-37.

HASKELL, T. R. 1964: The Cretaceous geology of the Whakarora area, Wairarapa, New Zealand. N.Z. Journal of Geology and Geophysics 7 (3): 554-60.

HUI.STON, J. R.; McCABE, W. J. 1972: New Zealand potassium-argon age list-1. N.Z. journal of Geology and Geophysics 15 (3): 406-32.

JoHNSTON, M. R. (in press): Sheet N159 Tinui and part Sheet N15S Masterton. "Geological map of New Zealand 1:63 360". N.Z. Department of Scientific and Industrial Research, Wellington.

JoHNSTON, M. R.; BROWNE, P. R. L. 1973: Upper Jurassic and Cretaceous conglo­merates in the Tinui-Awatoitoi district, eastern Wairarapa (Note). N.Z. Journal of Geology and Geophysics 16 (4): 1055-60.

LENSEN, G. ]. 1962: Sheet 16 Kaikoura. "Geological map of New Zealand 1:250 000". N.Z. Department of Scientific and Industrial Research, Wel­lington.

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ONGLEY, M. 1936: Blairlogie gas vent. N.Z. Geological Survey Annual Report 30: 9-12.

SPEDEN, I. G. 1973: Distribution, stratigraphy, and stratigraphic relationships of Cretaceous sediments, Western Raukumara Peninsula, New Zealand. N.Z. Journal of Geology and Geophysics 16 (2): 243-6S.

(in press): Cretacem•s stratigraphy of Raukumara Peninsula. N.Z. Geological Survey Bulletin 91.

STEVENS, G. R. 1965: The Jurassic and Cretaceous belemnites of New Zealand and a review of the Jurassic and Cretaceous belemnites of the Indo-Pacific Region. N.Z. Geological Survey Paleontological Bulletin 36. 2S3 p.

SuGGATE, R. P. 1958: The geology of the Clarence Valley from Gore Stream to Bluff Hill. Transactions of the Royal Society of N.Z. 85: 397-408.

WELLMAN, H. W. 1959: Divisions of the New Zealand Cretaceous. Transactions of the Royal Society of N.Z. 87: 99-163.

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