Eolian and silica deposition of ODP sites in the central North Pacific@en

Sediments recovered at Ocean Drilling Program Sites 885/886 (central North Pacific Ocean at 44°41'N, 168°14'W and 44°41'N, 168°16'W, respectively) record eolian deposition during the Cenozoic and late Mesozoic. We constructed a record of eolian MAR, which is a proxy for aridity/humidity of the climate in the continental source area. Eolian fluxes are low during the Late Cretaceous through Eocene, reflecting humid conditions in the source area. During the Oligocene, more arid climates prevailed at the source area, as indicated by increased eolian accumulation. The \"Diatom Dump\", an interval of enhanced silica deposition mainly apparent in the northwest Pacific, is reflected in the record at Sites 885/886 by two- to fivefold higher opal fluxes compared with younger and older sediments. Increased eolian deposition starting at 3.5 Ma and culminating at 2-2.6 Ma are coincident with the onset of Northern Hemisphere glaciation. Sites 885/886 lie 10° north of sites examined previously for the history of eolian deposition in the central North Pacific and therefore allow enhanced understanding of the latitudinal variation of the wind system.采自大洋钻探计划（Ocean Drilling Program, ODP）885/886站位（分别位于北太平洋中部，坐标为44°41'N、168°14'W与44°41'N、168°16'W）的沉积物，保存了新生代与晚中生代的风尘沉积记录。我们构建了风尘堆积速率（eolian MAR）序列，该序列可作为大陆物源区气候干湿状况的代用指标。晚白垩世至始新世期间，风尘通量处于较低水平，反映出物源区彼时的湿润气候环境。渐新世时期，物源区气候转为干旱主导，风尘堆积量的升高恰好印证了这一气候转变。‘硅藻堆积层’（Diatom Dump）是主要出现在北太平洋西北部的硅质沉积增强时段，在885/886站位的沉积记录中，该层位的蛋白石通量较其上下的新旧沉积物高出2至5倍。3.5 Ma左右启动的风尘沉积增强事件，并于2~2.6 Ma达到峰值，与北半球冰川作用的起始时间相吻合。885/886站位相较于此前用于研究北太平洋中部风尘沉积历史的站位偏北10°，因此该数据集可进一步增进我们对风系纬度变化规律的认知。