Isotope record of Nd-Sr-Pb in deep sea sediments from the Pacific (Table 2)

Pelagic clay of the east-central Pacific province is shown to be a mixture of three primary detrital components, reflecting continental source areas in Asia, North America, and Central and South America. Relative contributions from each source area are a function of geography, and this distribution appears to have remained constant over the past five million years, despite changing flux rates. A Q-mode factor analysis of downcore records for Pb, Sr, and Nd isotopes identified three factors that account for 98% of the total variance. These factors represent the radiogenic isotopic signatures of 1) late Cenozoic Asian dust, which dominates in the central North Pacific; 2) North American continental hemipelagic/eolian sources, restricted mainly to the easternmost North Pacific at ~30 °N latitude; and 3) Central and South American sources, restricted to areas east of ~100 °W longitude. South of the Intertropical Convergence Zone (~6 °N), the Asian dust signature diminishes abruptly. We conclude that late Cenozoic Asian dust sources can be isotopically differentiated downcore from both North American and South and Central American sources in the eastcentral Pacific. This approach has a utility for identifying changes in long-term Cenozoic atmospheric circulation patterns.

研究表明，东中太平洋区域的远洋黏土（pelagic clay）由三种主要碎屑组分混合而成，其物源分别对应亚洲、北美洲以及中南美洲的大陆区域。各物源区的相对贡献受地理因素影响，且尽管通量率发生变化，这种分布模式在过去五百万年间似乎保持稳定。通过对铅（Pb）、锶（Sr）和钕（Nd）同位素的岩芯剖面记录进行Q模式因子分析（Q-mode factor analysis），识别出三个因子，它们解释了总方差的98%。这些因子分别代表以下物源的放射性同位素特征：1）晚新生代亚洲粉尘，其在中北太平洋占主导地位；2）北美大陆半远洋/风成物源，主要局限于北纬约30度的北太平洋最东部区域；3）中南美洲物源，局限于西经约100度以东的区域。热带辐合带（Intertropical Convergence Zone）以南约北纬6度处，亚洲粉尘的特征突然减弱。我们的结论是，在东中太平洋的岩芯剖面中，晚新生代亚洲粉尘物源可通过同位素特征与北美及中南美洲物源区分开来。该方法可用于识别新生代长期大气环流模式的变化。