Laminated diatomaceous sediments occur intermittently in the Bering Sea over the past 5 million years. A varve (annually deposited) origin for the laminae has been suggested, but there is currently no consensus. Here, we report results of a study of two laminated intervals dating from ∼528 ka and ∼ 782 ka from IODP Site U1340 on the Bowers Ridge. We combine conventional micropaleontological methods with scanning electron microscope analysis that resolves the seasonal cycle of flux events recorded and demonstrates an annual origin for the laminae. Resting spores of Chaetoceros spp., and more rarely of Thalassiosira antarctica represent early spring blooms with the latter likely due to increased meltwater input. Diatom laminae containing concentrations of Shionodiscus trifultus, Thalassiosira spp., Actinocyclus curvulatus, and Neodenticula seminae, represent flux from the main spring-summer bloom episodes, with the latter indicating influx of seed populations from the North Pacific Alaskan Stream. Concentrations of Coscinodiscus spp. in the uppermost part of the diatom laminae represent “Fall Dump” sedimentation of these stratified-adapted diatoms in response to break down of summer stratification in autumn/early-winter storms. The lithogenic laminae represent mainly winter deposition and rare earth element analysis suggests provenance from the southern Bering Sea shelf and the Aleutian Arc. Productivity was high in the studied intervals with total mass fluxes around 5 times higher than modern values. Variation in lamina thickness and diatom composition contain periodicities of 2–8 years, as well as a bi-decadal variability likely related to influence of the Pacific Decadal Oscillation.

过去 500 万年来，白令海断断续续地出现了层状硅藻土沉积物。有人提出了薄片的 varve（每年沉积）起源，但目前尚未达成共识。在这里，我们报告了对鲍尔斯岭 IODP 站点 U1340 的两个层状层段的研究结果，这些层状层段的年代可追溯至～528ka和～782ka。我们将传统的微古生物学方法与扫描电子显微镜分析相结合，解决了记录的通量事件的季节性周期，并证明了纹层的年度起源。 Chaetoceros spp. 的休眠孢子，以及更罕见的Thalassiosira antarctica 代表早春开花，后者可能是由于融水输入增加。含有大量 Shionodiscus trifultus、Thalassiosira spp.、Thalassiosira spp. 的硅藻片a> spp 的浓度。硅藻层最上部的“Fall Dump”代表了这些适应分层的硅藻的“秋季倾倒”沉积，以响应秋季/初冬风暴中夏季分层的分解。成岩纹层主要代表冬季沉积，稀土元素分析表明其来源来自白令海南部陆架和阿留申群岛弧。研究区间的生产率很高，总质量通量比现代值高出约 5 倍。纹层厚度和硅藻成分的变化包含 2-8 年的周期性，以及可能与太平洋十年涛动的影响有关的十年间变化。Coscinodiscus 代表春夏主要花期的通量事件，后者表明种子种群从北太平洋阿拉斯加溪流涌入。 Neodenticula seminae 和 Actinocyclus curvulatus