New Caledonia basin-Fairway ridge : structural and...

INTBRNATIONAL SYMPOSIUM ON GEODYNAMICS IN SOUTH-WEST PACIPIC

NOUMEA (NEW CALEDONIA) 27 AUGUST.2 SEPTRMBER 1976 BDITIONS TECHNIP, PAUS 1977, pp. 145-154

NEW CALEDONIA BASIN-FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

2 2 SEP, “77 C. RAVENNE(’), C.E. de BROlNt2), J. DUPONT(3) A. LAPOUILLE‘3’ and J. LAUNAYl3’ o. w. s. T. o. b9.

Abstract Austradec I and II marine seismic surveys ca r r i ed out i n 1972 and 1973 by the IFP-CEPM-ORSTOM group i n the southwes tem Pa- c i f i , c cont r ibü ted t o the explora t ion of the s t r u c t u r a l elements loca ted between Lord Howe R i s e and Norfolk Ridge, i nves t iga t ed the sedi- mentary f i l l s i n accordance with da t a from DSDP boreholes , and poin ted out the impor- tance of volcanic alignments,

The leading s t r u c t u r a l element discovered by these surveys was the Fairway Ridge begin- ning at Fairway Reef i n the North, Two of us (C.E. de Broin and C. Ravenne) consider t h a t t h i s r idge prolongs i n t o West Norfolk Ridge towards the South,

The discovery of t h i s r idge thus leads us t o divcde the New Caledonia Basin i n t o an eas- tem New Caledonia Basin sensu s t r i c t o and a w e s tem Fairway Basin.

A s tudy of seismic f ac i e s and da ta from DSDP boreholes enables us t o suggest t h a t t he f i l l i n t he New Caledonian Basin sensu s t r ic- t o i s mainly of t u r b i d i t e o r i g i n and t h a t i n the Fairway Basin i s mainly pe l ag ic except i n i t s southem pa r t . The proport ion of elements derived from volcanism i s considerable i n both basins .

Las t ly , we c l ea r ly de l imi t two volcanic alignments, i .e. one loca ted i n the e a s t e m p a r t of Lord Howe Rise, and the o the r i n the westem p a r t of Norfolk Ridge.

I n t h i s paper we f i r s t descr ibe the s t ruc- t u r a l elements, and then w e show how magnetic da t a confirm our hypotheses , before examining the sedimentary series.

GEOGRAPH I C SI TUATI ON

The area inves t iga t ed i s loca ted i n the South West P a c i f i c ( f i g , 1). It i s framed by Lord Howe R i s e i n the West and Norfolk Ridge i n the East. It i s bounded i n the North at the l a t i t u d e of New Caledonia and i n the South by the northermost t i p of West Norfolk Ridge.

GEOTECTONIC SITUATION

This area i s loca ted i n a mixed marginal zone context bounded by a cont inenta l area, Aus t r a l i a i n the West and oceanic zones of re- cent o r i g i n i n the Eas t , i.e. t he Tasman Sea, the South F i j i Basin and the North Loyalty P1 ateau.

The c r u s t va r i e s i n thickness t h e r e , ran- ging from a semicont inental thickness of 20 t o 30 km under Lord Howe R i s e and Norfolk Rid- ge t o a semioceanic thickness of about 15 km under the bas in (Shor e t a l . , 1971) .

(1) Institut Français du Pétrole, 1 et 4 avenue de Bois-Préau, 92502 Rueil-Malmaison, France

( 2 ) Société Nationale Elf Aquitaine (Production), 26 avenue des Lilas, 64001 Pau, France

( 3 ) Office de la Recherche Scientifique et Technique Outre-Mer, B.P. AS, Noumea Cedex, New Caledonia

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NEW CALEDONIA BASIN-FAIRWAY RIDGE : STRUCTURAI, AND SEDIMENTARY STUDY

PREVIOUS WORK

It cons is ted mainly i n bathymetry (maps by Scripps I n s t i t u t i o n of Oceanography and New Zealand Oceanogr. I n s t . ) and i n seismic re- f r a c t i o n (Shor e t a l , , 1971). On the o the r hand the DSDP boreholes a re a valuable con- t r i b u t i o n t o the understanding of the l i t ho lo - gy and of marine unconformities (R.E. Burns, J .E . Andrews e t a l . , 1973). Besides the seis- mic r e f l e c t i o n p r o f i l e s by Mobil O i l Co publ i - shed by F.P. Bentz (1974) , no o the r seismic r e f l e c t i o n survey has been done i n t h i s area.

DATA

For t h i s paper , we have made use of B- LZ'OM se ismic l i n e s recorded by ORSTOM and es- pec ia l ly of Austradec mul t i t r ace seismic-re- f l e c t i o n p r o f i l e s recorded by t h a t I f l - c~p) ! - ORSTOM.

An i n t e r p r e t a t i o n o t the magnetic anoma- l i es was attempted, a l s o using da ta from the Austradec and Georstom p r o f i l e s .

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STRUCTURAL FEATURES

1. Fairway Ridge.

This i s a new fea tu re revealed by our sur- veys on the bas i s of seismic r e f l e c t i o n and magnetism da ta , We began t o suspect i t s exis- tence i n 1973 (Dubois e t a l . , 1974).

Fairways Ridge i s a major s t r u c t u r a l fea- t u r e i n the South West P a c i f i c as a re Lord Howe R i s e and Norfolk Ridge ( f i g . 2 and 3) . It d i v i d e s the New Caledonia Basin i n t o two sub-basins and p lays an important r o l e as a b a r r i e r i n the d i s t r i b u t i o n of sediments.

It appea r s as a basement r idge (seismic f ac i e s , magnetic s igna tu re , geologic framework) about 70 km wide ( f i g . 4 , 5 a, b , c) and near- l y 1,500 km long.

The magnetic s igna ture of t h i s r idge i s . c h a r a c t e r i s t i c . This aspect w i l l be discussed la te r i n t h i s paper.

The r idge runs almost p a r a l l e l t o Norfolk Ridge and follows the same d i r e c t i o n a l chan- ges.

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The c e n t r a l p a r t of the r idge , which i s the longes t p a r t (about 700 k m ) , t rends t o the North, It abrupt ly changes i t s d i r e c t i o n at the l e v e l of Fairway reef West of New Ca- ledonia . I n the North i t i s loca l i zed under- neath the f lank of L a n d s d m Bank which bounds Lord Howe R i s e . Fairway Ridge ends abrupt ly at 19" S l a t i t u d e , i n a roughly East-West t rending f r a c t u r e zone.

To the South, West Norfolk Ridge extends i n the exac t prolongat ion of Fairway Ridge. Two of us (C. Ravenne and C.E. de Broin) con- s i d e r t h a t West Norfolk Ridge i s the Southern p a r t of Fairway Ridge. The o t h e r t h ree authors divide i t i n t o two s t r u c t u r a l élements of d i f - f e ren t o r i gin.

The ax is of Fairway Ridge divides i n t o two sub-para l le l alignments of basement i n West Norfolk Ridge where they d e l i m i t a narrow ba- s i n . West Norfolk Ridge curves South East i n i t s southern t i p ( f i g . 2 ) .

Fairway Ridge i s shallow at both ends and progress ive ly becomes deeper and bur ied t o 3,000 m i n i t s p iddle p a r t . Under a t h i n l aye r of sediments, i t s substratum has a characte- t i s t i c seismic f ac i e s ( f i g . 5 a , b y c) with a s t rong r e f l e c t o r overlying a b l i n d zone. I n t h i s i t d i f f e r s from Lord Howe Rise and Nor- f o l k Ridge where the substratum revea ls orga- n i zed r e f l ec t ions . The presence of these re- f l e c t i o n s and the thickness of the underlying c r u s t from r e f r a c t i o n da ta (Shor, 1971) ap- pears t o prove t h a t both these r idges a re of the semicont inental type. Despite the absence of seismic r e f r a c t i o n on Fairway Ridge, magne- t i c anomalies and the absence of any organized r e f l e c t i o n suggest t h a t the substratum i s mainly of vo lcanic o r i g i n ( c f . the s tudy of magnetic anomalies descr ibed hereunder).

The sedimentary cover on t h i s r idge i s very t h i n a t e i t h e r end, up t o two t o th ree hundred meters, It gradual ly becomes th i cke r i n the middle p a r t where the r idge i s bu r i ed under the sedimentary series of the New Cale- donia Basin. _ _ _ __

It i s obvious t h a t the o r i g i n of t h i s r idge l i es wi th in the geotec tonic evolu t ion of the South West P a c i f i c , bu t it i s even mo- re d i f f i c u l t t o say how it w a s c rea ted , Per - haps i t w a s a f r o n t a l bulge of oceanic c r u s t i n f r o n t of a subduction zone loca ted t o the East as suggested by Dubois e t a l . , (1974). However, perhaps i t i s a former volcanic alignment l i k e the Lord Howe Guyots o r poss ib ly a former volcanic a r c corresponding t o one of the subduction s tages between the Aus t ra l ian and P a c i f i c p l a t e s ,

.NEW CAMDONIA BASIN-FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

2. Fairway Basin ( f i g . 2 , 3 , 4, G a , b y c ) .

We cal l Fairway Basin t h a t p a r t of New Ca- l edonia Basin "sensu l a to" which i s loca ted between Lord Howe R i s e and Fairway Ridge. We keep the name South New Caledonia Basin f o r the southem p a r t of t h i s bas in between West Norfolk Ridge and Lord Howe R i s e .

I t s s i z e and t rend a re i d e n t i c a l t o those of the r idges surrounding i t because it occu- p i e s the e n t i r e depression between these r id- ges.

According t o our p r o f i l e s , i t appears t o end i n the North at Landsdown Bank.

I n i t s c e n t r a l p a r t , West of Norfolk Is- land, the bas in l i es under 3,200 m of water. This depth decreases gradual ly towards i t s ends, although l eve l ing o f f at around 3,000 m i n f r o n t of West Norfolk Ridge. The deepening of Fairway Ridge i n i t s middle p a r t elimina- tes i t s ro l e as a b a r r i e r between Fairway and New Caledonia Basins, thus changing the d i s - t r i b u t i o n of the sediments.

The basement of t h i s bas in i s c l e a r l y de- l imi ted i n some p laces by a powerful re f lec- t o r revea l ing considerable d i f f r a c t i o n s ( f i g . 6 b) . In o the r p laces , the substratum i s poor- l y defined because i t i s masked by d i f f r a c t i n g r e f l e c t o r s (volcanic series ?) o r by th i ck se- r ies.

The sedimentary f i l l ( f i g . 2 ) i s general- l y about 2,000 m thick. Two much th i cke r areas w e r e found. One i n the n o r t h e m p a r t of the bas in r i g h t of f the southern t i p of New Cale- donia i s probably l inked t o the degradation of the r e l i e f s of Landsdown and Fairway Banks as w e l l as t o the Volcanic outflows underl ining the contact between Lord Howe R i s e and Norfolk Ridge, the o the r loca ted t o the South of West Norfolk Ridge wi th a thickness of about 3,000 I% of sediments i s probably l inked t o the de- gradat ion of West Norfolk Ridge and the proxi- mity of New Zealand.

A rise of the basement w e s t of the North- em t i p of West Norfolk Ridge forms a small th reshold t h a t divides the bas in i n i t s leng- thwise d i re c t ion,

A t the contac t between Fairway Basin and Lord Howe Rise, we found a volcanic alignment on the e a s t e m f lank of Lord Howe R i s e (high ax is i n f i g . 2 ) . Some evidence of t h i s volca- nism has been presented by F. Bentz (1974). This alignment occurs i n the shape of a s t r i n g

of seamounts bu r i ed wi th in a sedimentary se- ries. The upper p a r t of t h i s s t r i n g roughly corresponds t o the Oligocene unconformity. So- me of these volcanoes were l a t e r r eac t iva t ed by subsequent t e c t o n i c a c t i v i t y ,

3. Piew Caledonia bas in Sensu S t r i c t o ( f i g . 2 , 3 , 4 , 7 a, b y c) .

What we ca l l New Caledonia Basin sensu s t r i c t o i s the bas in between Fairway Ridge and Norfolk Ridge. This bas in i s much smaller i n s i z e (about 1,000 km long) than the o the r

a s t r u c t u r e s because Wanganella Bank between West Norfolk Ridge and Norfolk Ridge ( f i g . 3) c loses i t of f i n i t s southem p a r t . To the North i t i s closed of f a t the f r a c t u r e zone bounding Fairway Ridge. The northern end of the. New Caledonia Basin, i .e. the p a r t loca- t ed o f f New Caledonia, has previously been descr ibed (Dubois e t a l . , 1970). W e should j u s t no te the presence of a small bas in ( f i g , 7 c) t o the South of New Caledonia, between New Caledonia Basin sensu s t r i c t o and Norfolk R$dge, as was revealed by Dupont e t a l , , (1975).

New Caledonia Basin S.S. has an even f l a t bottom a t a depth of about 3,600 m.

Under a sedimentary blanket 2,000 t o 3,000 m t h i c k , a basement can be seen t h a t i s high- l i g h t e d on the seismic p r o f i l e s by a s t rong r e f l e c t o r ( f i g , 7 a) on top of a g r e a t many d i f f r ac t ions .

4. Norfolk Ridge ( f i g . 2, 3 , 4).

It s t r e t c h e s nea r ly 1,500 km between the North Western t i p of New Zealand and New Cale- donia. Two of us (C.R. and C.E. de B.) assume t h a t Norfolk Ridge i s l inked t o the North Wes- tem t i p of New Zealand through the Vening Meinesz f r a c t u r e zone. The corresponding of f - set might have been caused by the opening up of t h e Tasman Sea f a r t h e r t o the South West, To the North, it extends i n t o New Caledonia. Norfolk Ridge i s dissymmetric. The sedimentary series the re are t i l t e d towards the Eas t , The western edge i s made up by an alignment of volcanic i n t r u s i o n s , This alignment appears t o extend i n t o the western volcanic " s i l l on" (P. Routhier, 1973) of New Caledonia.

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NEW CALEDONIA BASIN - FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

The d i f f e r e n t sedimentary series and t h e i r age were recent ly descr ibed by J. Dupont e t al. (1975). The pos i t i on of t h i s r idge l i nk ing two areas having almost exac t ly the same geo- l o g i c a l h i s t o r y (New Caledonia and the Auck- land region) (A.R. L i l l i e and R.N. Brothers , 1970) as w e l l as the sedimentary series cha- r a c t e r i s t i c s from seismic da ta suggest t h a t t h i s r idge has undergone the same geologica l h i s t o r y as what i s known at i t s two ends.

Norfolk Ridge separa tes two very d i f f e r e n t sedimentary provinces , i .e. i n the West New Caledonia Basin with i t s th i ck sedimentary f i l l , and i n the E a s t a complex region bare of sediments and apparently of recent o r ig in .

ANALYSIS OF MAGNETIC ANOMALIES

Magnetic anomalies have made a very valua- b l e cont r ibu t ion t o the s t r u c t u r a l knowledge of the u n i t till now c a l l e d New Caledonia Ba- s i n . The magnetic r e l i e f i s q u i t e d i f f e r e n t from t h a t over the neighboring Lord How R i s e and Norfolk Ridge. Whereas across those rises the magnetic anomalies a re diverse and in t ense (Lapoui l le , t h i s volume; Launay e t a l , , t h i s volume) , here they a re w e l l character ized.

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A p o s i t i v e magnetic anomaly wi th a long wavelength , more than one hundred ki lometers long and seve ra l hundred gammas i n amplitude, extends along the length of New Caledonia Ba- s i n where it can be seen on a l l the p r o f i l e s c ross ing the bas in ( f ig . 8). This p o s i t i v e anomaly, sometimes divided i n t o two p a r t s , ta- kes i t s o r i g i n i n the e a s t e r n border of Lans- down Bank. A reduct ion i n the magnetic pole (Galdeano, 1974) of the p r o f i l e c ross ing the a rea above Lansdown Bank, assuming the rema- nent magnetism t o be o r i en ted l i k e the pre- s e n t magnetic f i e l d , a l s o induces a s l i g h t phase displacement of the magnetic anomalies t o the East ( f i g , 9). We can thus suggest t h a t the corresponding geological s t r u c t u r e has i t s o r i g i n on the eas t e rn border of Lansdown Bank, A t h ree kilomete p r o f i l e (Galdeano , 1974) emphasizes the breadth of t h i s anomaly whose corresponding geologica l s t r u c t u r e i s thus q u i t e deep-sea- ted. A geological model def ined by i t s magne- t i c s u s c e p t i b i l i t i e s (Lapoui l le , t h i s volume) w i l l prove these conclusions t h a t the so-cal- l e d Fairway R i s e s t r u c t u r e should be sea t ed t o the North East and under Lansdowne Bank, It i s represented by a magnetic s u s c e p t i b i l i t y ran- ging t o 13.10-3 c.g.s. corresponding t o a ba-

upward prolongat ion of t h i s

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s a l t i c body, I t s magnetic c h a r a c t e r i s t i c s thus suggest t h a t Fairway Ridge i s a magnetic rise.

p r o f i l e s which cross i t (Lapouille , t h i s volu- me), and i t jo ins West Norfolk Ridge i n the South v i a the Vening Meinesz Frac ture Zone.

This i s shown accross the f i l t e r e d regional (4

4

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This magnetic rise i s separa ted from the cont inenta l Lord Howe R i s e by a narrow bas in we c a l l Fairway Basin. This bas in i s charac- t e r i z e d by a negat ive magnetic anomaly of high amplitude , seve ra l hundred gannnas , whose wave- length i s equal t o the bas in width.

The reduct ion i n the pole of t he p r o f i l e c ross ing Lansdown Bank ( f ig . 9) r eeea l s the cnaracteristic magnetic minimum of the bas in , while the upward prolongat ion of t h i s p r o f i l e removes the high frequencies of the va r i a t ions e

which are thus due t o a topographical e f f e c t , s ince the sea f loo r i s very close t o the s e a le- vel there . The substratum, as shown by magne- t i c anomalies, i s thus h ighe r i n the nor thern -+

p a r t of the basin.

The New Caledonia Basin sensu s t r i c t o , which i s then reduced t o the area loca ted bet- ween Fairway R i s e and New Caledonia-Norfolk Ridge, i s charac te r ized by a lack of w e l l - m a r - ked magnetic anomalies. This area i s magneti- c a l l y w e l l cont ras ted and d is t inguished from the neighboring r idges which a re marked by l a rge p o s i t i v e anomalies ou t l in ing Fairway Ridge on one hand and b a s a l t i c u p l i f t s on the s lope between Norfolk Ridge and the New Cale- donia Basin on the o the r hand. The magnetic va r i a t ions he re are extremely s l i g h t , the am- p l i tudes very low and the wavelengths no t w e l l defined. The g rea t depth of the b a s a l t i c base- ment (over la in by a th ick sedimentary layer ) could expla in the relative lack of magnetic va r i a t ions ,

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r h

SEDIMENTARY S E R I E S

I n the bas ins , seismic p r o f i l e s enabled us t o d i s t ingu i sh up t o th ree main sedimenta- ry series separa ted by unconformities. Data from DSDP boreholes of l e g 2 1 , toge ther wi th the known land geological h i s t o r y ( L i l l i e and Brothers , 1970) enable us t o propose the fo l - lowing ages f o r the main unconformities.

- Unconformity 1 , which i s found through- out the e n t i r e area examined, corresponds i n

NEW CALEDONIA BASIN-FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

the boreholes t o a gap between the Upper Eo- cene and bower and Middle Oligocene. The un- conformity i s e spec ia l ly obvious on the r id- ges and on the edges of the basin. I n the mid- d le of the bas ins the series are o f t en confor- mable, and the problem can be r a i s e d of the poss ib l e ex is tence of a more complete series.

- Unconformity 2 , i s probably s i t u a t e d i n tli8 Upper Cretaceous. It i s sometimes confused wi th the acous t ic basement,

- Unconformity 3, which i s not reached i n the boreholes , corresponds on seismic p r o f i l e s t o d i f f e r e n t phenomena. Whereas i n New Caledo- n i a Basin and on Fairway Ridge i t ove r l i e s an obvious acous t i c basement, i t appears on the contrary on Lord Howe R i s e , Norfolk Ridge and the western border of Fairway Basin t o correspond t o a s t rong unconformity separa t ing series of s ed imnta ry o r i g i n (Dubois e t a l , , 1974). It i s no t obvious t h a t t h i s unconformi- t y observed on the seismic sec t ions corres- ponds t o a synchronous phenomenon throughout the whole area.

DSDP boreholes , seismic f ac i e s and for- mations known on land suggest t h a t sediments a re mainly pe l ag ic i n Fairway Basin and i n the c e n t r a l p a r t of New Caledonia Basin. Near emerged land (New Caledonia) o r very shallow r idge (West Norfolk Ridge) the f i l l looks more t u r b i d i t i c ( f i g . 7 c ) , probably wi th a high proport ion of vo lcanic elements.

The t w o upper series t h i n out considerably on the r idges , and unconfomi t ies 1 and 2 are o f t en found t o merge, On the o the r hand, main- l y on Lord Howe R i s e , t h e r e i s a considerable developmnt of the underlying series under un- conformity 3 (Dubois e t al , , 1974).

CONCLUSI ON

The area under inves t iga t ion i s a t r ans i - t i o n zone i n which the convergence of the AUS- t ra l - Indian cont inenta l p l a t e and the oceanic P a c i f i c p l a t e i s revealed during i t s evolu t ion by a succession of f o s s i l i s l a n d arcs with as- soc ia t ed s t r u c t u r e s and elements detached from the Aus t ra l i an margin.

The s t r u c t u r a l elements making up t h i s re- gion are, f o r the most p a r t , s t r e t ched out along a submeridian d i rec t ion .

They bend towards the North West i n the North and towards the South Eas t i n the South. These bends appear t o have been caused by sprea- ding i n the North Loyalty and North F i j i Pla- teaus i n the North and by the c rea t ion of the Tasman Sea i n the South.

Three of these elements whose s t r u c t u r e i s descr ibed i n t h i s paper - Fairway Basin and Ridge and New Caledonia Basin S.S. - gradual ly become deeper i n t h e i r middle p a r t a t the l a - t i t u d e of Norfolk I s land .

Fairway Ridge, which i s the s t r u c t u r a l element t h a t we r evea l , i s probably an element aqsociated with an ac t ive f o s s i l margin (fron- t a l bulge, former alignment: o r vo lcanic a rc ) .

Fairway Basin and New Caledonia Basin S.S., whose substratum reveals no organized r e f l ec - t i o n and whose c r u s t i s t h i n , a r e bas ins probably c rea ted i n connection with the bu i l - ding of former i s l a n d arcs ( in t e r - a rc o r mar- g ina l bas in ) , The sedimentary f i l l i nd ica t e s t h a t the age of c rea t ion w a s o lde r than l a t e Cretaceous and at most j u ra s s i c .

We thank ORSTOM, IFP, C P , f o r permission t o publ i sh

t h i s paper. W e are indebted t o the o f f i c e r s and crews of the N.O. Cor io l i s and Noroi t from CNEXO and t o J.P. F a i l and R. Donatien which were geophysicis ts during Austradec II cru ise .

W e are g ra t e fu l t o M. Poulet and G. Grau f o r t h e i r c r i t i ca l reading of t h i s paper.

B I B L I OGRAPHY

BENTZ (F.P.),- 1974. Marine geology of t he Southern Lord Howe R i s e , South West Paci- f i c , i n The Geology of Continental Mar- gins . C.A. Burk and C.L. Drake Ed i to r s , S p r i n g e r V e r Z a g , New York, pp. 537-547.

BURNS (R.E.), ANDREWS (J.E.) e t al.- 1973. I n i t i a l r epor t s of the Deep Sea D r i l l i n g P r o j e c t , vol. XXI, U.S. Govt. P r i n t i n g O f f i c e , Washington , D. C.

DUBOIS (J , ) , RAVENNE (C.), AUBERTIN (F . ) , LOUIS (J . ) , GUILLAUME (R.) , LAUNAY (J.) and MONTADERT (L.) .- 1974. Cont inental Margins nea r New Caledonia, i n The Geolo-

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NEW CALEDONIA BASIN-FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

gy of Continental Margins. C.A. Burk and C.L. Drake E d i t o r s , S$T=inge.er Verzug, New York, pp. 521-535.

DUPONT (J.), LAUNAY (J.), RAVENNE (C.) and De BROIN (C.E.) .- 1975. Données nouvel les s u r l a r i d e de Norfolk (Sud Ouest Pac i f ique) . C.R. Acad. Se. , P a r i s , t. 281 , série D y pp. 605-608.

GALDEANO (A.) .- 1974. Traitement des données aéromagnétiqueq : méthodes e t applica- t i ons . Th'he'se 3eme cycZe, Univers i té P a r i s V I .

LAPOUILLE (A.) .- 1977. Magnetic Surveys over t he rises and bas ins i n the South West Pa- c i f i c , i n t h i s volume.

- . . . .

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Seismic traverses across t h e Northern Lord Howe R i s e and comparison wi th the Southern p a r t , i n t h i s volume. r . .

LILLIE (A.R.) and BROTHERS (R,N.).- 1970. The geology of New Caledonia. New ZeaZand J . &OZ. Geophys. , vol. 13, no I , pp. 145- 183.

ROUTHIER (P.).- 1953. Etude géologique du ver- s a n t occidental de l a Nouvelle Calédonie entre l e co l de Boghen e t l a poin te d'Ara- ma, Mem. Soc. geoZ. Fr. NouveZZe Se'&, t. 32, fasc. 1-3, f e u i l l e s 1-34 Mem., n o 67, pp. 1-271.

SHOR (G.G.), KIRK (H.K.) and MENAkD (H.W.).- 1971. Crus ta l s t r u c t u r e of t he Melanesian area, J . Geophys. Res., vo l , 76, no 1 1 , pp. 2562-2586.

. .. . . ... .

150

NEW CALEDONIA BASIN-FAIRWAY RIDGE : STRUCTURAL AND SEDIMENTARY STUDY

166' 1" 186. 170. 176'

FAIRWAY RIDGE

FAIRWAY BASIN

I I II ISOPACH MAP OF

TOTAL SEDIMENT THICKNESS

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151

152

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FAWAY BASIN I FAIRWAY RIDOE I

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FAIRWAY RIDGE

NEW CALEWNIA BASIN

SCHEMATIC

DRAWOS OF REFLECTON

PROFILES FROM THE NORTH

TO THE SOUTH

Fig. 4

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153

Fig.8 Magnetic anomalies in the area of New Caledonia Basin and surroundings .

-K nariu AUS m5

SV, ,. sl...

i-

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Original prof i le

Fig.9 Reduction to the North magnetic pole and upwards prolongation of magnetic profile AUS 105

I54

w FNRWAY BASIN 4

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8 o, d

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5

Sous le patronage de Office de la Recherche Scientifique et Technique (autre-Mer Bureau de Recherches GBologiques et Mini&res Institut FranGais du PBtrole Inter-Union Commission on Geodynamics.

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