An Annotated Speleological Bibliography of Oceania, 1987, Bourke, R. Michael

A preliminary annotated speleological bibliography is presented for Oceania. The region covered extends from Irian Jaya (Indonesia) in the west to the Galapagos Islands (Equador) in the east. There are 268 references given from the following countries and territories: Antarctica, Belau, Cook Islands, Easter Island, Fiji, French Polynesia, Galapagos Island, Guam, Irian Jaya, Marian Islands, New Caledonia, Niue, Solomon Islands, Tonga, Vanuatu, Western Samoa, Wallis and Futuna.

La karstification de l'île haute carbonatée de Makatea (Polynésie française) et les cycles eustatiques et climatiques quaternaires, 1991, Dessay J. , Pouchan Y. , Girou A. , Humbert L. , Malezieux J.

THE KARST 0F MAKATEA ISLAND (FRENCH POLYNESIA) AND THE CLIMATIC AND GLACIO-EUSTATISM SETTING - Located in the Central Pacific, in the northwestern part of the Tuamotu Archipelago, Makatea island (148° 15’ W - 15° 50’ S) is an uplifted, karstic, carbonate construction of Early Miocene age, which reaches 113m in height. From 1906 to 1966, phosphate deposits were exploited on Makatea Island. These phosphate deposits (apatite) overlaid the Miocene series and filled the karstic cavities in the higher regions of the island. Several traces of ancient shorelines can be observed on Makatea: 1/ three different reef formations, which reach about +27m, +7m, +1m above the present mean sea level and respectively dated 400,000 ± 100,000 yr BP, 140,000 ± 30,000 yr BP, between 4,470 ± 150 yr BP and 3,720 ± 13O yr BP; 2/ four distinct marine notch lines on the Early Miocene cliff at about +1m, +7m, +27m and +56m (or +47m on the west coast caused by tilt) above the present mean sea level; 3/ two exposed marine platforms respectively at +29m and +7m above the present mean sea level. The ages of the former makatean shores are inferred by using: (1) the Pacific glacio-eustatic sea-level curve for the last 140,000 yr BP, (2) the Pacific oxygen isotope curve for the last 900,000 yr BP, and (3) a constant uplift rate during the Pleistocene. In this way, according to their age and elevation, the sea-level indicators at about +1m, +7m and +27m (+29m) above the present mean sea level can be respectively related to the Holocene transgression (Flandrian) dated between 6,000 and 1,500 yr BP, to the last Pleistocene interglacial period (Sangamon) dated between about 130,000 and 110,000 yr BP, and to a Middle Pleistocene interglacial period (Yarmouth) dated between about 315,000 and 485,000 yr BP. If we assume that a sea level similar to the present occurred during the Yarmouth inter-glacial period, the uplift rate is valued at 0.085 mm/yr to 0.056 mm/yr. Thus the sea-level associated with the marine notch at about +56m (+47m) may be about 650,000 yr to 1 M.y. old and can be associated with another Pleistocene interglacial period (Aftonian). Consequently, as indicated by the former shores, the sea level fluctuations can be related to the major glacio-eustatic quaternary events. This climatic and eustatic setting is used to explain the karst observed on the Makatea island. Carbonate dissolution and essentially vertical karst genesis were the result of the superposition of several cycles. Each cycle was initially composed of a solution of the carbonates during an interglacial period, followed by a drainage of the saturated solutions during the marine regression associated with the consecutive glacial period. Nevertheless, this scheme is not enough to explain the specific morphology of the makatean karstic cavities and we suggest using insular phosphatisation to explain this karst genesis. It is generally accepted that phosphate rock deposits on coral reef islands are the result of chemical reaction between seabird guano and reef limestone. Furthermore, petrographic and stable isotope studies suggest several generations of phosphorite formation and reworking episodes in the history of these deposits. The primary deposition of phosphates must have begun during a glacial period. This deposition was followed by some redistribution of phosphorites during the interglacial period and by additional precipitation of apatite from meteoric waters. This assumed process of phosphogenesis is consistent with both the field observations and the geodynamic evolution of Makatea. Thus, the particular morphology of the makatean karst can be the result of the dissolution of the carbonates caused by phosphoric acid etching. This acid is derived from the evolution of the phosphorites during the pleistocene interglacial periods.

MURUROA ATOLL (FRENCH-POLYNESIA) .1. STRUCTURE AND GEOLOGICAL EVOLUTION, 1992, Buigues D, Gachon A, Guille G,

From a geographical point of view, the atoll of Mururoa belongs to the Tuamotu archipelago. In its largest dimension Mururoa (28 x 10 km) is oriented N080-degrees-E, a direction which is different from that of the other atolls of the Tuamotu, generally oriented parallel to the Pacific plate motion, N130-degrees-E. The atoll of Mururoa is built on a submarine plateau of 130 km long and 30 km wide. The western side of this plateau is 90 km long and N080-degrees-E oriented, the eastern one 40 km long and N095-degrees-E oriented. Three deep main structures of the atoll are revealed by strong aeromagnetic anomalies elongated and oriented once more N080-degrees-E. They represent ancient riftzones, similar to the present time Hawaiian ones. The most important of them, situated at southern end of the atoll, is the prolongation of the eastern plateau. The principal petrographic facies have been defined from the numerous drill holes bored in the upper 1,100 m. From the base to the top are represented volcanic deposits, a volcano-sedimentary serie of both carbonate and volcanic origin and finally reefal carbonates (limestones and dolomites). The volcanic facies represent successively submarine, transitional and aerial volcanic activity. They are commonly affected by early stage of hydrothermalism, due to lava-sea-water chemical interaction, and are frequently supported by differentiated dykes, occasionally interrupted by reefal limestones. The main geometrical distribution of the facies through the atoll and the radiochronology lead to the following model of formation : during early stages of the atoll building two main separate edifices emerged before joining and forming a single volcano. This double structure was similar to the present time morphology of Tahiti. The volcanic activity ceased 10.6 Ma ago, an age which perfectly suits a hot spot origin, at present located to the south-east of Pitcairn island