Non-carbonaceous abyssal fine-grained sediments cover vast parts of the North Pacific’s deep oceanic basins and gain increasing interests as glacial carbon traps. They are, however, difficult to date at an orbital-scale temporal resolution and still rarely used for paleoceanographic reconstructions. Here, we show that sedimentary records of past geomagnetic field intensity have high potential to improve reversal-based magnetostratigraphic age models. Five sediment cores from Central North Pacific mid-latitudes (39-47°N) and abyssal water depths ranging from 3900 to 6100 m were cube-sampled at 23 mm resolution and analyzed by automated standard paleo- and rock magnetic methods, XRF scanning, and electron microscopy. Relative Paleointensity (RPI) records were determined by comparing natural versus anhysteretic remanent magnetization losses during alternating field demagnetization using a slope method within optimized coercivity windows. The paleomagnetic record delivered well interpretable geomagnetic reversal sequences back to 3 Ma. This age span covers the climate-induced transition from a biogenic magnetite prevalence in the Late Pliocene and Early Pleistocene to a dust-dominated detrital magnetic mineral assemblage since the Mid-Pleistocene. Volcaniclastic materials from concurrent eruptions and gravitational or contouritic sediment re-deposition along extinct seamount flanks provide a further important source of fine- to coarse-grained magnetic carriers. Surprisingly, higher proportions of biogenic versus detrital magnetite in the late Pliocene correlate with systematically lowered RPI values, which seems to be a consequence of magnetofossil oxidation rather than reductive depletion. Our abyssal RPI records match the astronomically tuned stack of the mostly bathyal Pacific RPI records. While a stratigraphic correlation of rock magnetic and element ratio logs with standard oxygen isotope records was sporadically possible, the RPI minima allowed to establish further stratigraphic tie points at ~50 kyr intervals. Thus, this RPI-enhanced magnetostratigraphy appears to be a major step forward to reliably date unaltered abyssal North Pacific sediments close to orbital-scale resolution.

中文翻译：

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通过地磁古强度确定北太平洋深海沉积物的年代：磁化载体、上新世气候变化和底栖氧化还原条件的影响

非碳质深海细粒沉积物覆盖了北太平洋深海盆地的大部分地区，并且作为冰川碳捕获越来越受到关注。然而，它们很难以轨道尺度的时间分辨率确定日期，并且仍然很少用于古海洋学重建。在这里，我们表明过去地磁场强度的沉积记录具有改进基于反转的磁地层年龄模型的巨大潜力。来自中北太平洋中纬度 (39-47°N) 和深水深度范围为 3900 至 6100 m 的五个沉积岩芯以 23 mm 的分辨率进行立方采样，并通过自动标准古和岩石磁性方法、XRF 扫描、和电子显微镜。相对古强度 (RPI) 记录是通过在优化的矫顽力窗口内使用斜率方法比较交替磁场退磁过程中的自然与非磁滞剩磁损失来确定的。古地磁记录提供了可很好解释的地磁反转序列回到 3 Ma。这个年龄跨度涵盖了气候引起的从晚上新世和早更新世的生物成因磁铁矿向中更新世以来以尘埃为主的碎屑磁性矿物组合的转变。沿已灭绝海山侧翼同时发生的喷发和重力或等高岩沉积物再沉积产生的火山碎屑物质提供了细粒到粗粒磁性载体的另一个重要来源。出奇，上新世晚期生物成因磁铁矿与碎屑磁铁矿的比例较高与系统性降低的 RPI 值相关，这似乎是磁化石氧化而不是还原耗竭的结果。我们的深海 RPI 记录与大部分深海太平洋 RPI 记录的天文调谐堆栈相匹配。虽然岩石磁性和元素比率测井与标准氧同位素记录的地层相关性偶尔有可能，但 RPI 最小值允许在 ~50 kyr 间隔建立进一步的地层连接点。因此，这种 RPI 增强的磁地层学似乎是可靠地确定接近轨道尺度分辨率的未改变的北太平洋深海沉积物年代的重要一步。我们的深海 RPI 记录与大部分深海太平洋 RPI 记录的天文调谐堆栈相匹配。虽然岩石磁性和元素比率测井与标准氧同位素记录的地层相关性偶尔有可能，但 RPI 最小值允许在 ~50 kyr 间隔建立进一步的地层连接点。因此，这种 RPI 增强的磁地层学似乎是可靠地确定接近轨道尺度分辨率的未改变的北太平洋深海沉积物年代的重要一步。我们的深海 RPI 记录与大部分深海太平洋 RPI 记录的天文调谐堆栈相匹配。虽然岩石磁性和元素比率测井与标准氧同位素记录的地层相关性偶尔有可能，但 RPI 最小值允许在 ~50 kyr 间隔建立进一步的地层连接点。因此，这种 RPI 增强的磁地层学似乎是可靠地确定接近轨道尺度分辨率的未改变的北太平洋深海沉积物年代的重要一步。