Age control points and sedimentation rates of ODP Hole 145-887B (Table 1)

Hole 887B of the Ocean Drilling Program (ODP) comprises a 44 m (750 kyr) long continuous section recovered from the Patton-Murray Rise, an elevated plateau that is largely isolated from turbidite deposition. The Patton-Murray area is centered under the Alaska Gyre, a region characterized by the domal upwelling of nutrient-rich waters. Marked increases in productivity and rapid settling of biogenic matter are suggested throughout the section by the episodic accumulation of diatomaceous oozes up to ~1 m thick that are accompanied by barium enrichments. Significant delta13Corg maxima in the major diatomaceous bands suggest that mixedlayer [CO2(aq)] may have been drawn down significantly during some of the productivity events. The episodes of enhanced productivity at Site 887 occur synchronously with short-lived minima in planktonic foram delta18O, suggesting a direct link to low salinity, or less likely, warming, events in the Gulf of Alaska. There is no obvious explanation for the events, but they may be related to seasonal incursions of meltwater from Alaska. We speculate that episodic input of meltwater- or dust-borne iron from Asian or Alaskan sources may have promoted the extraordinary diatom production events recorded in the sedimentary record.大洋钻探计划（Ocean Drilling Program, ODP）的887B钻孔，取自巴顿-默里海隆（Patton-Murray Rise）——一处基本不受浊流沉积影响的抬升高原，获取了总长44米、对应75万年沉积时长的连续岩心序列。巴顿-默里海域位于阿拉斯加环流（Alaska Gyre）中心，该区域以营养盐丰富水体的穹状上升流为典型特征。整个岩心序列中，厚度可达约1米的硅藻软泥间歇性堆积并伴随钡富集现象，指示此处曾出现显著的初级生产力提升与生源物质快速沉降过程。主要硅藻层位中出现显著的有机碳同位素δ¹³C_org最大值，表明部分生产力爆发事件期间，混合层水体中的溶解态二氧化碳[CO₂(aq)]浓度可能大幅降低。887B钻孔处的生产力增强事件，与浮游有孔虫氧同位素δ¹⁸O的短期低值同步出现，这暗示其与阿拉斯加湾的低盐度事件直接相关，亦不排除与区域变暖事件相关的可能性。目前尚无明确的成因解释，但该类事件可能与阿拉斯加地区季节性融水入侵存在关联。我们推测，源自亚洲或阿拉斯加地区、经由融水或风尘搬运的铁元素间歇性输入，可能促进了沉积记录中所记录的异常硅藻勃发事件。