CARBONATE BUILDUP OF ATOLLS AND GUYOTS IN THE NORTHWESTERN PACIFIC - PRELIMINARY-RESULTS FROM ODP LEG-144

During Leg 144, 20 holes located on 10 sites (871 to 880) allowed the study of the origin of volcanoes and the sedimentary evolution of 5 gu yots. The sedimentary evolution of these guyots yields a similar scena rio, irrespective of their age (Aptian-Albian at MIT in the Japanese G roup; Campanian-Maastrichtian and Palaeocene-Eocene in the Marshall Is lands): after emergence and subaerial exposure of the volcanic basemen t, carbonate deposits occur during gradual flooding of the guyot and t hen cease suddenly and give way to the deposition of pelagic sediments . Classical atoll features were especially recorded at Wodejebato Guyo t (Marshall Islands, sites 873 to 877), which displays two perimeter r idges partly composed of coral-rudist reef facies and enclosing a cent ral lagoon; it may correspond to an analog of the Recent Pacific atoll s.