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.马尼希基高原（Manihiki Plateau）是一片面积达60万平方千米的平缓平顶地貌，坐落于西赤道太平洋海域。丹杰尔岛、拿骚岛、苏沃罗夫岛以及马尼希基岛均从该高原的南部区域隆起。高原顶面区域海拔介于2400~3000米，周围海域水深约5500米。高原顶面被厚约1千米的沉积物覆盖。高原东西两侧的沉积物岩芯中含有红黏土，而高原顶面则覆盖着有孔虫软泥（foraminiferal ooze）。来自东断崖的岩芯与拖网采样中发现的矿物颗粒与岩石碎片表明，在南纬13°以北构成高原东缘的海岭下方，伏存有基性火成岩。对高原东断崖3000米以深海域以及东侧深海丘陵区的海底摄影与拖网采样结果显示，此处分布有大量锰结核（manganese nodules）。多数海底摄影资料均显示有深海流活动的痕迹。尽管岩芯中存在大量基性火山活动的证据，但高原的形态显然受断裂作用控制。高原东缘海岭上白垩纪化石的发现表明，该高原的夷平作用应发生于白垩纪时期或更早。本次研究数据源自维玛号（Vema）第18次科考航次，共包含20个沉积物岩芯、2次拖网采样、4次底拖网作业以及15个海底摄影站位。