The siliceous sponges and crinoids from the Chénier Ravine (France, Lower Callovian) are used here as biological markers to characterize the palaeoenvironment of the adjacent and contemporaneous La Voulte Lagerstätte that is remarkable for its unique soft-bodied fauna (e.g. worms, cirrate octopods, vampire squids). Sponges are abundant with dominant hexactinellids (80%) and lithistids (20%). Four lines of fossil evidence, supported by Recent analogues, indicate that this sponge community inhabited deepwater setting under dysphotic or aphotic conditions: (1) the dominance of hexactinellids; (2) the prevalence of cone shaped and erect morphologies that usually characterize Recent bathyal sponges; (3) the close similarities with Recent hexactinellids from the continental slope and; (4) the lack of encrustation by photophilic organisms. Attachments of sponges on hard substrate (e.g. crystalline basement) and their preservation in soft sediments (e.g. muds) indicate heterogeneous bottom conditions. The Chénier fauna also contains small stalked, asymmetric cyrtocrinid crinoids that are known to live on hard substrates in bathyal environments such as the SW Pacific steep seamounts. Convergent palaeoenvironmental clues obtained from both crinoids and siliceous sponges support the notion that the La Voulte area, including the La Voulte Lagerstätte, was situated in the upper part of the bathyal zone near the slope-basin transition with a water depth most probably exceeding 200 m. Supporting evidence from heterogeneous substrates and complex fault systems indicate a depositional environment along the external part of the slope where steep topographies and blocks usually favour the settlement of cyrtocrinid crinoids and hexactinellid sponges. La Voulte may therefore be one of the rare and extremely precious Mesozoic Lagerstätten to have fossilized a deep marine environment.

CALSUB, MUSORSTOM 6

The following results are deduced from radiocarbon and oxygen 18 curve datings obtained in Quaternary hemipelagic deposits cored off SW and SE slopes surrounding New-Caledonia: _ the radiometric age of total sediment (periplatform ooze + calcareous planctonic remains) exceeds that derived from the 8(18)0 curve yielded by Orbulina universa; _the rate of sedimentation strongly decreases, principally off southwestern coasts, during the last 16,000 years. This is a probable consequence of the screen-effect of the reefal Quaternary belt, enhanced by the Flandrian transgression.

BIOCAL, BIOGEOCAL

Submarine slopes and basins off New-Caledonia (South-Western Pacifie); morphology, biosedimentary environments, sedimentation During the Biocal deep-sea cruise off New-Caledonia, fauna and sediments were sampled and Seabeam maps were drawn. The first geological results are as follows: - block-faulting determines the morphology of the slopes, their erosion and the transport of sediments along them towards the Loyalty basin plain; - erosion is predominant in the studied areas of the western Caledonian slopes and along the slopes off Lifou island where the canyons are broad and scattered, whereas in front of the "passe de Thio", through the reefal barrier, a relatively high detritic influx transits through several narrow canyons; - the Loyalty basin has been explored along the Thio-Lifou transect; it exhibits a flat bottom and is fed mainly from the eastern Caledonian slopes by calcareous and argilaceous turbidites, which spread eastward over nearly 50 km and interfinger with hemipelagites; - the sediments are constituted by 5 distinct components: 15 to 50% of detritics from New-Caledonia (mainly clay minerais, iron oxydes and silicate minerais); 15 to 25% bioclastic silts and sands derived from the reefal ring and from the lagoon; mixed bioclasts ( 1 to 20%) furnished by benthonic communities living on the slopes and in the basin; planktonic debris (30 to 75%) with a dominant fraction composed of foraminifers and pteropods; and volcanic debris (0,5 to 10%). A sedimentation rate of about 6cm/1000 years (between 16000 and 5000 years B.P.)has been estimated from the explored sector of the Loyalty basin.

BIOCAL

Submarine slopes and basins off New-Caledonia (South-Western Pacifie); morphology, biosedimentary environments, sedimentation During the Biocal deep-sea cruise off New-Caledonia, fauna and sediments were sampled and Seabeam maps were drawn. The first geological results are as follows: - block-faulting determines the morphology of the slopes, their erosion and the transport of sediments along them towards the Loyalty basin plain; - erosion is predominant in the studied areas of the western Caledonian slopes and along the slopes off Lifou island where the canyons are broad and scattered, whereas in front of the "passe de Thio", through the reefal barrier, a relatively high detritic influx transits through several narrow canyons; - the Loyalty basin has been explored along the Thio-Lifou transect; it exhibits a flat bottom and is fed mainly from the eastern Caledonian slopes by calcareous and argilaceous turbidites, which spread eastward over nearly 50 km and interfinger with hemipelagites; - the sediments are constituted by 5 distinct components: 15 to 50% of detritics from New-Caledonia (mainly clay minerais, iron oxydes and silicate minerais); 15 to 25% bioclastic silts and sands derived from the reefal ring and from the lagoon; mixed bioclasts ( 1 to 20%) furnished by benthonic communities living on the slopes and in the basin; planktonic debris (30 to 75%) with a dominant fraction composed of foraminifers and pteropods; and volcanic debris (0,5 to 10%). A sedimentation rate of about 6cm/1000 years (between 16000 and 5000 years B.P.) has been estimated from the explored sector of the Loyalty basin. Oceanologica Acta, 1989, 11, 2, 131-140.

BIOCAL

This preliminary study deals with deep-sea biogenic traces and bioturbation off New Caledonia. All the data were obtained during the Biocal multidisciplinary (biology/geology) cruise aboard the oceanographie vessel Jean-Charcot (summer 1985). The studied area was chiefly along a transect extending from Thio to Lifou across the Loyalty basin. An initial inventory of superficial biogenic traces and sorne reflections concerning their distribution are given. Certain traces correspond to ichnogenera rarely or not found on modern oceanic floors but weil known in deep-sea fossil deposits (Paleodictyon, Urohelminthoida). In contrast with plain pelagie environments, the bioturbation is very variable. Indeed, the benthic life is frequently disturbed by turbidites and mud flows. Bioturbation is closely dependent on these sedimentary perturbations, and seems to be conditioned by the thickness and frequency of turbiditic deposits, size and shape of particles, and occurrence of a predepositional erosive phase. The effects of bioturbation have been analysed in connection with the obliteration of contacts between hemipelagites and turbidites and with the progressive disappearance of sorne thin turbiditic deposits. These observations and corresponding conclusions underline the interest of studying bioturbation for the analysis of fossil deposits containing hemipelagites and turbidites.

BIOCAL

BIOCAL, BIOGEOCAL

L'intérêt paléoenvironnemental des traces fossiles est bien connu des géologues. De même, l'importance de la bioturbation ou de la biocorrosion, dont elles sont l'expression, est considérable dans la dynamique sédimentaire. Or l'interprétation correcte de ces objets et de ces phénomènes ne peut progresser sans une meilleure connaissance de leurs équivalents actuels ou récents. Bien connus en milieu littoral, ils le sont beaucoup moins en milieu marin profond. D'où l'intérêt du programme ENVIMARGES qui a permis de multiples observations sur les pentes et dans les bassins au large de la Nouvelle Calédonie, dans un intervalle bathymétrique de moins de 100 m à plus de 3000 m. Les moyens d'investigation utilisés ont été nombreux et complémentaires. Les traces biologiques de surface ont ainsi été étudiées par observation directe depuis la soucoupe Cyana (CALSUB), par photographie automatique avec une caméra ponctuelle (BIOGEOCAL) ou commandée depuis la soucoupe (CALSUB), par film vidéo (CALSUB) et même par carottage grande surface Usnel (BIOCAL, BIOGEOCAL). Certaines traces profondes et les sédiments bioturbés ou biocorrodés ont été prélevés par carottage Usnel ou Kullenberg, dragage et chalutage (BIOCAL, BIOGEOCAL) ou directement par le bras préhensile de la soucoupe (CALSUB). Le but de ce travail est de rassembler les principales observations réalisées au cours des différentes campagnes et de présenter d'une manière synthétique et très simplifiée quelques résultats d'intérêt général.

BIOCAL, BIOGEOCAL, CALSUB

The deep-sea floor off New Caledonia was investigated during three successive multidisciplinary (biology/geology) cruises from 1985 to 1989: BIOCAL, BIOGEOCAL, and CALSUB. The main study area is the Loyalty Basin, which comprises a deep (2300 m) trough with a flat bottom and steep slopes topped by coral reefs. This basin is filled by a thick sequence of Recent hemipelagic muds and turbiditic sands, silts and muds. The slopes, which are strongly eroded, are locally covered by a thin layer of recent hemipelagic muds. Many biogenic traces occur in all muddy deposits. The trace assemblages of the basin bottom characterizes typical deep-sea ichnofacies with burrows, mounds, tracks, trails, and fecal castings. Two main ichnofacies are evidenced: a deep slope ichnofacies and a deep plain ichnofacies. The distribution of biogenic traces is probably controlled by the greater food supply on the slopes. The main trace makers that could be identified are holothurians and enteropneusts. Some traces, sampled by boxcoring, correspond to ichnogenera that are well known in fossil deposits (e.g., Paleodictyon and Urohelminthoida. One novel trace occurs on bathyal slopes, at depths exceeding 1300 m. It is made up of one mound and several holes forming a horseshoe ("Fer d Cheval") = the FC trace. It is strictly restricted to the slope, oriented according to the declivity, and very common between 1600 and 2000 m. So, this trace provides a very good environmental index. Bioturbation and erosion strongly hinder the preservation of these biogenic traces. Rapid burial by slightly or non destructive distal turbidites seems to be the only possible fossilization process.

BIOCAL, BIOGEOCAL, CALSUB

During the CALSUB cruise, bathyal environments were explored off the New Caledonia corallian platfdrms (southwestern Pacific). Green algae were observed down to a depth of 1 IO m, and red algae down to 145 m. Algal blocks, pebbles and sands contribute to sedimentation to a depth of 400 m and beyond, and are mixed with autochthonous fossils and bioclasts produced by bathyal benthos. Epibathyal fauna suggests similarities with Jurassic and Cretaceous fauna of Tethyan margins (Nautilus, pleurotomarian gastropods, sponges, brachiopods and crinoids…). Richness and abundance of the benthos are the highest in areas where currents are frequent between 300 m and 700 m (sometimes 10 to 20 terebratulid brachiopods per m2 or dense populations of echinoderms entirely covering the substrate). Such currents induce erosion of' substrate or bioclastic accumulations. Biocorrosion seems to be very active in erosion processes, especially on hard grounds. Burrows and traces show the importance of sediment bioturbation on slopes. The occurrence on bathyal slope of some taphonomic processes previously known from geological series and generally considered as closely related lo shallow-water environments should be emphasized.

CALSUB

L'exploration de la faune profonde de NouvelleCalédonie a débuté par des campagnes d'essai de 1977 à 1979 sur des fonds de 200 m à 1000 m au large de la Grande Terre, de l'île des Pins et des îles Loyauté (Intès, 1978). A partir de 1985, elle s'est élargie et intensifiée avec les campagnes MUSORSTOM 4 à 6 et CHALCAL (Richer de Forges, 1990), BIOCAL, BIOGEOCAL et SMIB, complétées par des observations directes à l'aide de la soucoupe plongeante Cyana lors de la campagne CALSUB. Nous ne donnerons ici que les grands traits de l'étagement de la macrofaune et de la mégafaune benthique en insistant sur les observations directes insitu lors de la campagne CALSUB et sur la liaison avec les caractères du milieu.

CALSUB