Flamand Benoit, Cabioch Guy, Payri Claude, Pelletier Bernard. (2008). Nature and biological composition of the New Caledonian outer barrier reef slopes. Marine Geology, 250 (3-4), p. 157-179. ISSN 0025-3227.
Auteurs
Flamand Benoit, Cabioch Guy, Payri Claude, Pelletier Bernard
Source
Marine Geology, 2008,
250 (3-4), p. 157-179 ISSN 0025-3227
The Grande Terre of New Caledonia is enclosed by one of the longest barrier reefs in the world. For the first time, the fore-reef slopes of this barrier reef have been sampled by dredging, from 40 to 320 m deep, in order to analyze their sedimentological and biological characteristics. The rocks and sediments can be divided into seven sedimentary facies: bindstones dominated by coralline algal crusts, bindstones dominated by foraminiferal crusts, bindstones dominated by bryozoan crusts, coral framestones, bindstones and interstratified packstones rich in skeletal debris, packstones/wackestones and grainstones rich in rock gravels. Radiocarbon dating performed on encrusting organisms (coralline algae and acervulmids) and corals provide ages relatively young. These ages confirm that the encrusting organisms are modem and the corals mainly dated of Holocene are reworked due to the instability of the fore-reef slopes, especially during storms. Because the biological assemblages are distributed according to a bathymetric range depending on light intensity, a model of distribution of modem encrusting calcareous organisms can be proposed from our observations and analyses. From the upper reef slopes to approximately 90 in, thick coralline algal crusts are dominant and distributed in three groups. Group C, the shallowest parts of the fore slopes, is mainly characterized by mastophorids (Hydrolithon reinboldii, H. cf. munitum, Lithoporella melobesoides, Aethesolithon cf. problematicum, Neogoniolithon sp. and undetermined species) and lithophylloids (Lithophyllum sp., L. pustulatum). Group B, composed of lithophylloids (Lithophyllum sp., L. cf. kotschyanum, L. cf. moluccence, L. pustulatum), Mesophyllum sp. and Peyssonnelia sp. occurs from 15 to 40 in. Group A, rich in Mesophyllum sp., M. cf mesomorphum, Peyssonnelia sp. and Sporolithon sp. is characteristic of deep reef slopes up to 90 in. Below approximately 90 in, when the light intensity decreases, the encrusting foraminifera acervulinids progressively replace the coralline algal crusts. Such a model is particularly useful to interpret and reconstruct the past Quaternary reef environments rich in crusts of coralline algae and/or foraminifera.
