Annotated record of the detailed examination of Mn deposits from R/V Vema Cruise 18 in the Manihiki Plaeau area, Pacific Ocean

The Manihiki Plateau, a 600,000 km2 smooth and nearly flat-topped feature, lies in the west equatorial Pacific. Danger, Nassau, Suvorov and Manihiki Islands rise from the southern part of the plateau. Oceanic depths of about 5500 m surround the 2400-3000 m summit area. The top of the plateau is capped by approximately one kilometer of sediment. The sediment cores to the east and west of the plateau contain red clay but the top of the plateau is covered with foraminiferal ooze. Mineral grains and rock fragments in cores and dredge hauls from the east escarpment indicate that basic igneous rocks underlie a ridge that forms the eastern edge of the plateau north of 13°S. Bottom photographs and dredge hauls below 3000 m on the east scarp of the plateau and in the abyssal hills to the east reveal abundant manganese nodules. Most of the botton photographs show evidence of deep-sea currents. The plateau's shape is apparently controlled by faulting although much evidence of basic vulcanism is present in the cores. The occurrence of Cretaceous fossils on the eastern ridge of the plateau indicates that the bevelling of the plateau must have occurred during or before Cretaceous time. Twenty cores, two dredge hauls, four bottom trawls and fifteen camera stations from the Vema cruise 18.