Annotated record of the detailed examination of Mn deposits from the ARIES-5 cruise among the West Pacific Guyots

The sea floor of the western Pacific is covered by five stratigraphic units: (l) an eastward thinning wedge of late Tertiary silty clay, primarily of volcanic origin, (2) a Cretaceous to Tertiary zeolitic red clay, (3) a Late Cretaceous to Tertiary chalk/chert sequence, (4) a Cretaceous clay, and (5) a basal chalk/chert sequence. The basal chalk was deposited on the young crust at the crest of the mid-oceanic ridge, while the upper chalk was deposited beneath the equator, and the abyssal clays were deposited in abyssal depths in mid latitudes. A kinematic model has been constructed that outlines the deposition of these units on growing crust, which not only was displaced westward away from the accretion center of the mid-oceanic ridge, but northward under the equator. The average northward component of motion for the Pacific plate has been 2 cm per year from 0 to 30 m.y. and 4.4 cm per year from 30 to 100 m.y. The deep-sea deposits of the Pacific are basically and systematically time transgressive. Claims of general synchroneity for either lithostratigraphy or acoustostratigraphy are rejected as inconsistent with both the drilling data and the kinematic model of Pacific pelagic stratigraphy. A few more well sampled holes in the ancient Pacific plate combined with an appropriately refined kinematic model should yield a 'rather detailed history of the Pacific plate since the Jurassic.

西太平洋海底分布有五套地层单元：(1) 一套向东逐渐减薄的晚第三纪粉质黏土楔，其物质成因以火山作用为主；(2) 一套白垩纪至第三纪的沸石质红黏土；(3) 一套晚白垩世至第三纪的白垩/燧石层序；(4) 一套白垩纪黏土；(5) 一套基底白垩/燧石层序。其中，基底白垩沉积于洋中脊轴部的年轻洋壳之上，而上覆白垩沉积于赤道下方海域，深渊黏土则沉积于中纬度的深海环境中。研究团队已构建一套运动学模型，用以刻画上述地层单元在增生洋壳上的沉积过程：该洋壳不仅自洋中脊增生中心向西发生位移，同时还在赤道区域向北漂移。0至30百万年期间，太平洋板块的平均北向运动速率为2厘米/年；30至100百万年期间，该速率提升至4.4厘米/年。太平洋深海沉积整体呈现系统性的时间穿时特征，认为岩石地层学或声波地层学具有普遍同时性的观点，与钻探数据及太平洋远洋地层运动学模型均存在矛盾，故不被采信。若能在古太平洋板块中获取更多采样质量优良的钻孔数据，并辅以精细化的运动学模型，即可重建侏罗纪以来太平洋板块相对详尽的演化历史。