JNTERNATIONAL SYMPOSIUM ON GEODYNAMICS W SOUTH-WEST PACIFIC NOUMEA (N6W CALEDONIA) 27 AUGIJST.2 SEPTEMRER 1976 EDITIONS TECHNIP, PARIS 1977, pp. 289-300

- GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN

INTRODUCTION sporadic traces of a#cient sea levels have been radiocarbon dated. It will be shown that, New Caledonia is an island stretched NW-SE, these dates, attributed to a high sea level at 400 km long by 50 wide in the South West * lan approximately 30,000 BP (LAUNAY and RECY, Pacific. The whole island is surrounded by a 1972), must be seriously re-examined. , barrier reef enclosing a very wide lagoon, f especially in the south western and northern parts of the island (see fig.]). The flat reef I - AGES OF THE REEF COMPLEXES is sub-outcropping and emerging on lowest low tide in the western part of the island ; on A) - Uplifted reef complexes. the other hand, in the eastern part the bar- rier reef is not always outcropping and then A coral sample, from an undercut near Hienghene collected at an elevation of 3.2 ? its upper part is lying some meters below the _/ sea-level. The lagoon is representative of the 0.3 my gave a radiocarbon date of 30,300 -t. new Caledonian "continental shelf", the bar- 2,700 years BP (1). The Uranium-Ionium date rier reef marking the transition line before of this sample, 100,000 years BP (BERNAT et the continental slope which dips steeply to al., 1976), is very doubtful since its mine- the basins surrounding New Caledonia. ralogical composition (74 Z aragonite, 26 % calcite) strougly indicates that crystalliza- The coast is surrounded by fringing reefs tion of secondary calcite has occured. This excepc in the sheltered bays where mangroves puts in doubt the radiocarbon age as well. are often found. The flat parts of those fringing reefs rise up in a gentle slope, South of New Caledonia and on the Isle of from 0.2 to 1 m above the zero of the French Pines frïnging reefs were uplifted. A Uranium Navy Survey Department (1). The highest part -Ionium age of 118,000 years BP was attribu- of those flat reefs where coral growth is no ted to a sample of coral from an elevation of longer possible, is partly covered up by the 20 m on the Isle, but the sample might have present beach. Above that one, between 2 and been contaminated since it contains 30 Z of calcite. A level of this age (BLOOM et al., I 4 m uplifted beaches are frequently found. Their attribution to Holocene (AVIAS, 1949 1973) at such an altitude would imply an and 1953 j ROUTHIER, 1953) has been confirmed uplift that might have been produced by the '2 by more recent data (LAUNAY and RECY, 1970, lithospheric bulge due to the underthrusting 1972 ; BALTZER, 1970 ; COUDRAY and DELIBRIAS, of the Australo-Indian plate beneath the Pa- 1972). Above, that is at between 3 to 6 my cific plate at the level of the New-Hebrides trench (DUBOIS et al., 1973,1974) and which is responsible of the uplift of the Loyalty (1) The zero of reference used in this paper Islands. is that of the French Navy Survey Dept. (1) Measurement made by Professor KIGOSHI'S The highest tidal range being 1.60m in N.Cal. Laboratory, Kagushin University - Tokyo.

(I) Laboratoire de Géologie Dynamique, Université Pierre et tarie Curie (Paris VI), 4 place Jussieu, 75230 Paris Cedex 05, (2) Office de la Recherche Scientifique et Technique Outre-Mer, B.P. A5, Noumea Cedex, New Caledonia

28 9 GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

B) - Data on the barrier reef flat reef, was found to have an age substan- All the available data on the barrier reef tially older than core drilled samples from originate from a unique borehole, 9 m deep, the upper part of that formation. This indi- on Tenia Islet (Western Barrier Reef). The cates that interpretations of radiocarbon formations are non indurated and holocene in ages of isolated coral samples should be made age. They overlay a 320,000 year old coral with caution. For example, the newly determi- formations (COUDRAY, 1973). The sea-level, at ned core age series in this area shows that that time, is assumed to be 5 or 6 m higher one cannot conclude that the south eastern than the present one (BLOOM et al., 1973,1974). part of New Caledonia was uplifted during the The resulting subsidence of the western bar- Holocene, as previously supposed by LAUNAY rier reef appears to have been about 14 m for and RECY (1 972). the last 120,000 years according to the Tenia Islet data, if it is assumed that the upper b) Core survey of the upper part of parts of this formation represent a flat reef the Touho fringing reef. which was near sea-level, i.e. + 5 m at 129, 1. Composition 120,000 years B.P. In the Touho area, about ten core dril- Observations carried out on the shores and lings from 5 to 10 m (I), were made in the in the lagoon support this hypothesis. They fringing reef which is several hundred meters reveal that the living reefs are found very wide there (see fig. 2). In general, the flat slightly below sea-level. The flat reefs, on- reef elevation varies from 0.2 m to 1 m bet- ly partially active, are found in the tigal ween the falling slope of the fringing reef range. Their tops could have formed durihg and the shore. Some of the drillings are in the higher sea-levels of the Hblocene, explai- shallow depressions 0.5 m deep. From the stu- ning why the majority now lie above current dy of the cores it can be ascertained that mean sea-level. On the other hand, observa- the upper part of the fringing .reef, at least tions made in the south east of New Caledonia, to the bottom of the deepest core (-12 m), on the Isle of Pines and in the Loyalty Is- consists of organogenous sands and coral de- lands (all uplifted reefs) show thy are not bris interspersed with continuous coral mas- dismantled by erosion. They behave just as ses. These are unusual in the inner part of karsts ; run-off is absent and infiltration the reef (near the shore) and increase in prevents surface erosion. In the context of number and thickness toward its outer part. the sea-level chronology of BLOOM et a1.,1973, Correlations between the lithological sequen- 1974, the resistance of the reef to erosion, ces of the different drillings are not easily implies that the ancient reef, which should be discernable. found at + 5 m, has actually subsided to -9 m. The following schematic descriptions of C) - Data on the fringing reef of the the S4 and S5 cores, made respectively in the eastern coast. outer and inner parts of the fringing reef (see fig. 2) show the extremes in the varia- a) Surface samples. tion of the lithological sequences : Data concerning the flat fringing reef are more numerous (Table I), but the results are ! ! not always coherent. ! Touho S 5 (shore side) ! - !Depth Lithology ! South of New Caledonia, at + 2 m, a conti- ! (from surface) ! nuous undercut running several kilometers can I------l be observed in ancient uplifted reef comple- ! 00-00.10 alluvium ! xes above the present flat reef. Two radiocar- 1 ! ;00.10-02.00 sand grains and coral debris ! bon age measurements on corals which have grown in the undercut after its formation, at 102.00-06-50 organogenous debris ! Tara (Tara, 1, 2, 3) and at Touaourou (69 Tou 1 ! 06,50-08.00 fine organogenous debris 15) gave netly different results though made i ! on sampleq from nearly at the same level !08.00-10.40 organogenous debris 1 (LAUNAY, RECY, 1972 ; COUDRAY, DELIBRIAS, ! ! ,10.40-10.50 coral mass 1973). New radiocarbon measurements made on ! the samples Tara 2,3 exhibited younger ages - -! 10.50-11.10 organogenous and coral debris! and ages closer to those found by COUDRAY and I ! 11.10-12.00 coral mass DELIBRIAS (1 973) for equivalent levels at ! Touaourou and also at Touho. The isolated co- ral sample 69 T l collected at Touho on the (1) The drillings were performed by OMNIUM TECHNIQUE. 2 90 GENETIC HYPOTHESIS ON THE ANCIENT AND WCENT REEF COMPLEXES IN NEW CALEDONIA

! ! Results shown in the following table give the extreme values : ! Touho S 4 (lagoon side) !, ! litho logical depth ! .. ! ! ! ! ! ! Sample 6180 ! A~'O !calCu- ! ! 00-0.40 flat reef ..1 ! ! coral/! water/!lated ! Age !- ! ! ! number ! PDB ! PDB ! ! ! 0.40-0.60 debris of coral branches toc ! ! ! ! ! ! ! ! ! 0.60-0.90 indurated organogenous sand ! ! ! ! !' ! ! 1 ! ! Touho, ! -3.34 ! -0.2:: ! 38'1 ! 3140k160 ! * 0.90-1 .O0 coral mass ! ! ! s9 (1) ! (max) ! ! ! ! ! 1.00-2.20 induraked organogenous sand ! ! ! ! ! ! ! and coral branches ! ! ! ! -0.7::::! 35O5 ! ! 1 ! ! ! ! ! ! ! 2.30-2.40 coral mass ! 1 ! ! ! ! ! ! 2.40-3.10 indurated organogenous sand ! ! Touho ! -4.64 ! -0.2:' ! 31"3 ! ! ! ! ! (5.) ! (min) ! ! ! 3.10-4.50 coral mass s4 ! ! ! ! ! ! ! ! ! ! ! ! ! -0.7::::! 28'9 ! 2660+ 60 ! ! ! ! ! ! ! 2. Age determinations and stable isotope measurements (table 11). .. average isotope composition of the oceanic Samples to be radiocarbon dated were selec- sea water (CRAIG, 1961). .e., ted in the massive coral from the cores. The **** isotopic composition of the Pacific sea samples are of aragonite without any trace of water measured in the approaches of Noumea. calcite. Measurements of isotopic ratios of 160/180, 12C/13C were also made. The follo- Since the calculated temperatures are rea- wing conclusions can be drawn from these re- sonable, with respect to the present tempera- sults : ture of the coral environment, it appears - The samples are all holocene in age. The- that the coral carbonate crystallised under re is no continuous age variation with depth, conditions near equilibrium with dissolved neither among the cores nor even within any carbonate. If one considers the general evo- single one. lution of the l80 content of the carbonate as a function of radiocarbon age, one finds - Mineralogy shows up that non recrystalli- (table 11) that this change was on the order sation has occured which would have transf or- of 1 2, between 6000 and 1500 years BP. The med aragonite into calcite. resulting apparent thermal change would aboÜt - The stable isotope contents can be inter- 4,Z"C. This represents a miximum variation preted in terms of crystallisation at or near since, during this period an influx of water isotopic equilibrium with the marine environ- derived from polar ice and having a very low ment when using available values for the iso- oxygen 18 contentamay have still occurred. topic composition of water. The paleotempera- tures equation (1) (CRAIG, 1965) : The ef,fect of the rise in temperature can thus be added to the effect of the lowering t = 16.9 - 4.2 (6 - A) + 0.13 (6 - A)' of the isotopic composition of since it ap- ives temperatures (OC) as a function of the pears from the paleotemperature equation that "0 content of the carbonate (6) and of the both effects influence the heavy isotope con- water (A). tents of the carbonates in the same sense. The corals, therefore, seem to have recorded (I) The oxygen 18 values are obtained from a logical and reasonable change of the holo- mass spectrometric measurements of CO2 cene climatic conditions,. This supports the gaz. For carbonates, the CO' is liberated by significance of the isotopic record of the reaction with phosphoric acid at 25°C ; for coral samples. water, the COZ is prepared by equilibration with the sample also at 25°C. These values The I3C contents show no particular ten- must be expressed with respect to the same dancy, however they suggest the corals to be working standard.of gazeous COZ. In this stu- free from isotopic exchange after the death dy, values of A and are expressed with res- of the organisms. pect to a working standard which was calibra- ted against CO2 derived from the PDB carbona- D) - Data on the fringing reef of the wes- te standard. tern coast.

291 GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

D) - Data on the fringing reef of the cent coral in the depressions in older coral western coast. flats e.g. Touho S 4 (6), and also by the ac- cumulation of shell material from above which a) Core drillings from Poya. is trapped in crevasses in the coral, e.g. Poya S 9 (F). In the Prowy bay area (Poya), not very far from the Croix-Haute cape, a series of conti- The growth of a reef complex takes place nuous core drillings were made to determine a during several thousand years. During this pe- place to build a wharf (1) (see fig. 3). riod significant reworking may occur in the solid phase or even in the liquid phase (bi- These drillings showed (see fig. 4) the carbonate produced by the dissolution of pre- existence of an ancient rise modeling thin and existing material). Thus coral is a marker not more or less indurated detritial materials easily used in the stude of sea leva1 changes (sands and sandstone). during the Holocene. Since coral growth occurs at various depths, it is apparent that only When submerged, the depressions of this ri- ages found for samples of the highest eleva- se were filled with primarily clay material, tions should be considered in sea-level stu- while the upper parts gay' bases for coral dies of the Holocene. Nevertheless it is a growths. good marker in the age determination of ,an- Core S 9, particularly rich in well preser- cient high sea levels. In this case the inac- ved coral material, has been chosen for a more curacy due to the mixing of coral of different detailed study. ages is of the same order as the error in ra- d iometr ic dating. That core, located on the flat reef side and isolated from the fringing reef by a chan- At Touho a level which dates from 5.000 nel, encountered 8.70 m of coral formation years BP at the bottom to 1.500 years BP at (see detailed section fig. 5). This formation the top is found between -8 m and the surface consists alternately of massive coral banks at +0.8 m'. These same ages are found between and of detritic layers containing shell and -13.3 m and the submerged surface of the reef coral debris. The samples studied come from at -6.3 m. Thus the dated holocene profiles at both these levels (see fig. 5). Touho S. 4 and Poya S 9 are of virtually the same thickness and correspond to the same ran- b) Age determinations and stable iso- ge of ages. The profiles are not found on the tope measurements (table III). same level at these tow locations since core The age profile is roughly coherent with S 9 is from the slope of the reef. depth and deals with the interval 5,400 to 1,300 BP corresponding to the growth of appro- The flat reef surfaces are of dead coral. ximately 7 meters of coral. The lowest sample, The present profils of the flats reefs were S 9 (H) at -24,9 m, il older than the radio- formed about 1500 years ago. Thus it appears carbon detection lïmit. The oxygen 28 content that sea-level has slightly decreased since variation is on the order of 0.5 %,. Calcula- then. This agrees with the drop in sea-level ted temperatures fall within the same range as of one to two meters between approximately the preceeding samples. The carbon 13 contents 500 to 1500 years BP froun by previous authors as well as the mineralogical assays of coral, (BALTZER, 1970 ; LAUNAY and RECY, 1970, 1972; containing exclusively aragonite, show that COUDRAY and DELIBRIAS, 1972). the original isotopic compositions has been conserved. Six thousand years ago, the fringing reef was still growing at approximately -8 m. In light of the velocity of the holocene sea- II - DISCUSSION level rise before 6000 years BP, it is impro- bable that reef growth began long before this A general tandancy for age to correspond date and at a far lower level. Drillings and with depth may be observed in the cores from observations made by divers show the outer si- the Touho and Poya fringing reefs. But the de of the fringing reef on the east coast of lack of a rigourous chronological order as a New Caledonia is thicker than 15 m. function of the sample depth is characteristic of reworkings and of allochtonous inputs, The holocene growth probably rests on an which may occur during the construction of a ancient reef .whose age is not known. The simi- coral flat. Age anomalies in the coral mass larity of the Tenia islet to the barrier reef proper may be explained by the growth of re- would suggest that this ancient fringing reef (1) Drillings were performed by the BACHY Com- was formed 120,000 years ago, corresponding a pany for De ROUVRAY'S firm. high sea level of +5 m (BLOOM et al. , 1973). 2 92 GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

Neglecting the effect of erosion on thg coral BERNAT M., LAUNAY J., RECY J., 1976 - Data- elevation it seems that the subsidence of ap- tion à 1'Ionium de quelques formations co- prowimately 14 m in the lost 120,000 years is raliennes émergées de Nouvelle-Calédonie not confined to the area of continental fle- et des îles Loyauté. C.R.Acad.Sc.Paris, xure seen on the barrier reef, but would have Série D, t.282, p.9-12. affected all of New Caledonia. This would not BLOOM A.L., BROECKER W.S., CHAPPEL J.M.A., include the southern part and the Islet of Pi- MATTHEWS R.K., MESOLELLA K.J., 1973 nes which were uplifted. Such an interpreta- - Quaternary Sea-Level Fluctuations on a tion would not agree with the age of 105,000 Tectonic Coast : New Th230, dates years measured at +3.2 m on the coral from a U234 from the Huon Peninsula, New Guinea. remnant flat reef at Hienghene, but this re- Abstracts of Ninth Congress International sult is questionable, as discussed above. On- Union for Quaternary Research. Christ- ly a drilling survey on the fringing reef and church, 2-10 December. the determination of ages with Ionium-Uranium on the lower levels would solve this problem BLOOM A.L., BROECKER W.S., CHAPPEL J.M.A., with more accuracy. MATTHEWS R.K., MESOLELLA K.J., 1974 - Quaternary Sea-Level Fluctuations on a Tectonic Coast : New 230Th/234Udates from

' CONCLUSIONS the Huon Peninsula, New Guinea - Quaterna- ry Research., 4, p.185-205. This study, which needs further informa- COUDRAY J., 1971 Nouvelles données sur la tions on several points, suggests the follo- - nature et l'origine du complexe récifal wing hypotheses : côtier en Nouvelle-Calédonie. Quat.Res., - A general subsidence of approxima- vol.], n02, p.236-246. tely 14 m may have affected the entire conti- COUDRAY J., 1973 Reef deposit, sedimentolo- nental plateau of New Caledonia during the - gy and quaternary events in New Caledonia. last 120,000 years. This subsidence represents Abstracts of Ninth Congress International the last part of a general quaternary episode Union for Quaternary Research. Christ- of 200 m which could have the formation of the church, 2-10 December. barrier reef, the inondation of the lower val- leys and major coast line retreat (phase III COUDRAY J. et DELIBRIAS G., 1972 - Variations of the physiographic model of ROUTHIER, 1953). du niveau marin au-dessus de l'actuel en Nouvelle-Calédonie depuis 6000 ans. C.R. - The holocene reef, 15 m in thick- Acad.Sc.Paris, Série D, t.275, p.2623- ness, is underlain by a subsided ancient reef 2626. platform. CRAIG H., 1961 Standard for reporting con- - Although the holocene deposits are - centration of deuterium and oxygen 18 in found or 2 meters above the current sea-level, natural waters. Science, 133, p.1833-1834. there is no evidence which proves that these deposits have undergone significant vertical CRAIG H., 1965 - The measurement of oxygen displacement since they may have been formed isotope paleotemperatures. in "Stable Iso- during the period of high sea-level which came topes in Oceanographic Studies and Paleo- to a close near 1.500 BP. temperatures''. Proceed. Symp, Spoleto 1965. E.Tongiorgi ed.,Consiglio Nazionale delle Ricerche, p.161-182. DAVIS W.M., 1925 Les côtes et récifs coral- REFERENCES - liens de la Nouvelle-Calédonie. Ann.Geogr. t.XXXIV, n"191, p.244-269 ; 332-359 ; AVIAS 1949 Note préliminaire sur quel- J., - 52 1-556. ques phénomènes actuels ou sub-actuels de pétrogenèse et autres dans les marais cÔ- DUBOIS J., LAUNAY J. , RECY J., 1973 - Les tiers de et , Nouvelle Calé- mouvements verticaux en Nouvelle-Calédonie donie. C.R. so". Soc.Géol.Fr., p.277-280. et aux îles Loyauté et l'interprétation de certains d'entre eux dans l'optique de la AVIAS 1959 - Les récifs coralliens de la J., tectonique des plaques. Cah.ORSTOM,Sér. Nouvelle-Calédonie et quelques-uns de leurs problèmes. Bull.Soc.Géol.Fr., p.424-430. géol., vo1.5, no], p.3-24. DUBOIS J., LAUNAY J., RECY J., 1974 - Uplift BALTZER F., 1970 Datation absolue de la - movements in New Caledonia Loyalty Is- transgression holocène sur la côte ouest - lands area and their plate tectonics in- de la Nouvelle-Calédonie. C.R.Acad.Sc.Paris terpretation. Tectonophysics, vo1.24, Série D, t.271, p.2251-2254. p.133-150. 2 93 GENETIC HIPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

LAUNAY J. et RECY J., 1970 - Nouvelles données en Nouvelle-Calédonie au Pléistocène supé- sur une variation relative récente du ni- I rieur et à l'Holocène. Rev.Géogr.Phys.Géo1. veau de la mer dans toute la région Nouvel- Dyn., vol.XIVy fasc.1, p.47-65. le Calédonie - îles Loyauté. C.R.Acad.Sc. ROUTHIER P.,' 1953 Etude géologique du ver- b Paris, Série t.270, p.2159-2161,. - Dy sant occidental de la Nouvelle-Calédonie LAUNAY J. et RECY J., 1972 - Variations rela- entre le col de Boghen et la pointe d'Ara- tives du niveau de la mer et néotectonique ma. Thèse. Mém. Soc,Géol.Fr. y n067.

..

TABLE I

Mineralogic. isotopic and radiometric radiocarbon data, on the fringing reef of the New Caledonia South Eastern Coast.

! Sample n' ! Altitude ! Calcite- i 6'*0/ i 6I3C/ ! Age14c(ans mesuré BP) iI Référence ! Place ! zéro S H ! Aragonite ! ! Nature 1 en !------I . PDB ! PDB ! ! I ! ! !C%! A% ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! '69 Tou IO coral ! !! ! ! ! ! ! , I Touaourou ! +1.8+0.2 !! I l ! 4380+llO (A) ! COUDRAY et ! ! in growth position ! !! ! ! ! ! DELIBRIAS ! ! I !! ! ! ! ! 1973 ! ! l !! ! ! ! ! ! ! Tara 2 coral ! !! ! ! ! ! ! I sub in situ ! +I z0.3 !O! 100 (D) ! -3.IO(C) ! -0.72(C) ! 73405140 (B) ! ! Y ! ! I! ! ! ! 49705120 (C) ! ! ! ! !! ! ! ! ! ! ! Tara 3 coral ! !! ! ! ! ! ! ! in growth position ! +0.6+0.2 !O! 100 (D) ! -4.03(C) !I -0.75(C) ! 6300+140 (B) ! ! ! ! !! ! ! ! 54705 90 (c) ! ! ! ! !! ! ! Tara I coral ! !! ! ! ! ! ! ! in growth position ! +2.1+0.2 !O1 100 (D) ! -3.53cC) I +0.59(C) i 7360+170 (B) i LAUNAY et ! ! ! !! ! ! ! ! RECY, 1972 ! ! 69 Tou 15 ! !! ! ! ! ! ! ! Touaourou coral ! !! ! ! ! ! ! ! sub in situ ! +2 zo.2 !I ! ! ! 3970+110 (A) ! COUDRAY et ! ! ! !! ! 1 ! ! DELIBRIAS ! ! ! !! ! ! ! ! 1973 ! ! ! !! ! I ! ! ! ! 69 T 1 Touho ! !! ! ! ! ! COUDRAY et ! ! coral apparently ! +I 20.5 !! ! ! ! 5400+120 (A) ! DELIBRIAS ! ! in situ ! I! ! I ! ! 1973 ! ! ! !! ! ! ! ! !

(A) DELIBRIAS C., Laboratoire du C.N.R.S. de GIF sur YVETTE (B) KIGOSHI K., Université Kagushuin, TOKYO (C) FONTES J.C., Laboratoire de Géologie Dynamique, Université P. et M. CURIE (D) A.M.D.E.L.. (Australian Mineral Development Laboratories) (E) MELIERES F., Laboratoire de Géologie Dynamique, Université P. et M. CURIE. I

L'

2 94 TABLE II

! ! ! I I ! ! ! ! TOUHO S4 (I) coral ! O. OE ! + 0.18 ! oc ! - 4.69 ! - 0.73 ! 1540 L 120 ! ! ! ! ! 100 A ! ! ! ! ! ! ! ! I ! ! ! ! TOUHO 54 (2) coral ! o. 35 ! - 0.09 ! oc ! - 4.38 ! - 1.02 ! 2550 2 90 ! ! ! ! ! !O0 A ! ! ! ! ! ! ! I ! ! ! ! ! TOUHO 54 (3) coral ! o. 95 ! - 0.69 ! oc ! - 4.25 ! - 1.99 ! 21!0+ 140 ! ! ! ! ! 100 A ! ! ! ! ! ! ! ! ! ! ! ! ! TOUHO 54 (4) coral ! 2.15 ! - 1 .89 ! oc ! - 4.04 ! - 1-15 ! 2200 5 130 ! I ! ! 1 ! 100 A ! ! ! ! ! ! ! ! ! ! ! TOUHO 54 (5) coral ! 3.15 ! - 2.89 ! oc ! - 4.64 ! - 1-50 ! 2660 2 90 ! ! ! ! ! !O0 A ! ! ! ! ! ! ! ! ! ! ! ! TOUHO S4 (6) coral 1 4.20 to.4.30 ! - 3.94 to - 4.04 I oc I - 4.42 ! - 0.45 ! 2170 120 ! ! ! ! ! 100 A ! ! ! ! ! ! ! ! ! I ! ! ! TOUHO S4 (7) coral ! 7.70 ! - 7.95 ! oc ! - 3.64 ! - 0.29 ! 6025 5 200 ! ! ! ! I 100 A ! ! ! ! ! ! ! ! ! ! I ! ! TOUHO S6 (I) coral ! 1.00 to 1.50 ! - 0.40 to - 0.90 ! oc ! - 3-57 ! + 0.34 ! 5730 L 150 ! ! ! ! ! 100 A ! ! ! ! ! ! ! ! ! ! ! ! ! TOUHO 56 (2) coral ! 3. 10 ! - 250 ! oc ! - 3.97 ! + 0.14 ! 4070 !O0 ! ! ! ! ! 100 A ! ! ! ! ! ! ! ! ! ! ! ! ! TOUHO S6 (3) coral ! 3.95 ! - 3.35 ! oc I -389 ! - 1-56 ! 5470 2 130 ! ! ! ! ! 100 A ! ! ! ! I ! ! ! ! ! ! I ! TOUHO S8 (1) coral ! 7.95 ! - 8.43 (+0.5 -0.1) ! oc ! - 3.85 ! - 0.39 ! 55005 110 ! ! ! 1% ! 100 A ! ! ! ! ! ! ! I ! ! ! ! ! TOUHO S9 (I) coral ! 0.20 ! - 0.98 (+0.7 -0.1) ! oc ! - 3.34 ! - 0.05 ! 31405 160 ! ! ! ! ! !O0 A ! ! ! ! l ! ! ! ! ! ! ! i TOUHO s9 (2) coral ! 2.90 ! - 3.68 (+0.7 -0.1) ! oc ! - 3.95 ! - ! .35 ! 3190 2 200 ! ! ! ! ! 100 A ! ! ! ! ! ! l ! I 1 I I

TABLE III

~~~ I ! I ! ! ! ! ! ! ! Depth of the ! ! ! ! Age 14c ! ! Sample no ! sample Level in meter i calcite ! PDB ! &l3C/ PDB i years BP ! ! ! in the drilling ! ! Z Aragonite I ! !

! ! ! I l ! ! ! ! Poya S9 (A) coral I 1.05 l - 6.30 ! DC ! - 3.92 ! - 0.65 ! 1315 L 170 ! ! ! ! ! 100 A ! ! ! ! ! ! I ! ! I I ! ! Poya S9 (B) coral ! 1.30 I - 6.55 ! oc ! - 3.54 ! - 1.05 ! 16502 50 ! I ! ! ! 100 A ! ! ! ! ! ! ! I ! I ! ! ! Poya S9 (C) shell tests ! 1.60 to 2.70 ! - 6.55 to 7.95 ! oc ! - 1.29 ! - 1.06 ! 1955 5 165 ! I ! ! ! 100 A ! ! ! I I l I 4 ! ! ! ! I ! Poya S9 (D) coral ! 3.05 ! - 8.30 ! oc ! - 2.58 ! - 0.48 ! 1635 _f. 220 ! ! ! ! ! IO0 A I ! l ! ! ! ! ! ! ! ! ! ! Poya S9 (E) shell tests ! 3.25 to 6 ! - 8.50 to 11.25 ! O C ! - 0.54 ! - 1.64 ! 1995 _f. 165 ! I ! ! ! 100 A ! ! ! I ! ! ! ! ! ! ! ! ! Poya S9 (FI shell tests ! 6.5 to 7.25 ! -11.75 to 12.50 ! O C ! - 1.77 ! - 1.54 ! 515 ! ! ! ! ! 100 A ! ! ! ! I l ! ! ! ! ! ! ! Poya S9 (J) coral ! 7.30 ! - 12.55 ! oc ! - 3.57 ! - 1.09 ! 5330 2 300 ! I l ! ! 100 A ! ! ! ! ! ! ! ! ! ! ! ! ! Poya S9 (F) coral ! 8.05 I - 13.30 ! oc ! - 3.70 ! - 0.06 ! 54105 Il0 ! I I ! ! 100 A l I ! ! 1 I !. ! ! ! Poya S9 (H) ! ! I ! ! indurated sand ! 19.65 ! - 24.90 ! oc ! ! 100 A I ! !

295 GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

Fig.. 1 - Locality map. - __.-

296 Fig. 2

J c

Fig. 3

Fig. 2 and 3 - Settlement of the drillings.

297 GENETIC HYPOTHESIS ON THE ANCIENT AND RECENT REEF COMPLEXES IN NEW CALEDONIA

Figure 4 SONDAGES DE LA BAIE DE PORWY (POYA) - ESSAI D'INTERPRETATION -

PLATIER ISOLE CHENAL RECIF FRANGEANT NIVEAU s10 DE LA MER s4 s5 s9 s3 s2 s1 O

IO I'

20 .

30

40

m ECHELLES

VERTICALE 1 1/1000

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MATtRlEL DETRITIOUE GROSS;ER(DcBRIS CORALLIENS ETCOqUlLLlERS 1 ~~~$~L~~>,'~~~~F~li~::EdEOR~~~vlER,~G~~~RA~ a ARßlLE CONTENANT DU MATtRlEL &TRITIQUE GROSSIER -- SIJRFACE DE TRANSGRESSION ARGILE CONTENANT DU MATkRlEL OtTRITlQUE FIN (SABLE)

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2 98 figure 5 BAIE DE PORWY (POYA 1 SONDAGE S9 COUPE- PARTIELLE

ECHANTI LLON POVA SSE (coqulllcs 1

-11.25 m. PAS O’ECHANTILLON - CORAIL NON DATABLE~ALTERE)

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..i ... OEERIS CORALLIENS ET COQUILLIERS CALCAIRE CONSTRUIT ALGAIRE CALCAIRE CONSTRUIT CORALLIEN

2 99 Sous le patronage de Office de la Recherche Scientifique et Technique Qutre-Mer Bureau de Recherches GBologiques et Mini&res Institut Franeais du Petrole Inter-Union Commission on Geodynamics.