This study presents a detailed sedimentary geochemical record of International Ocean Discovery Program (IODP) Site U1489, which was drilled off the northeast margin of Papua New Guinea (PNG). Focusing on the geochemical characteristics and the extent of chemical weathering of siliciclastic component, a total of 183 samples from the upper 84 m of Site U1489 are used to reconstruct the PNG sediment supplies to the tropical western Pacific over the last 4 Ma. Our geochemical results show a 3-stage variability in Site U1489 sediment composition, which are well related to regional tectonic and climatic changes. Stages III (~4.0–3.5 Ma) and II-A (~2.9–1.7 Ma) are characterized by more enhanced and variable contributions from mafic-rock sources than that of felsic-origin. This interval is shown to be accompanied by relatively rapid sediment delivery and more dynamic depositional environments that are possibly related to marginal mixing, coinciding with more frequent PNG tectonic events. In particular, increased contributions derived from ultra-mafic/mafic rocks are recorded between ~3.5 and 2.9 Ma, which is attributed to increased ophiolite input due to arc-continent collision. Accordingly, these results give a consistent but refined timing for an accelerated plate suturing at the eastern margin of PNG. By contrast, Stage I (~1.7–0 Ma) is characterized by a relatively constant background supply of finer particles, showing a persistent increase over time in the intensity of chemical weathering. This increased weathering trend is reported for the first time for the tropical regions of western Pacific, and it is interpreted as indicating a strengthening of the Walker Circulation in the past ~1.7 Ma. Overall, the interpretations of the siliciclastic fraction from Site U1489 presented in this paper provides crucial clues to distinguish the tectonic and climatic influences on the PNG sediment inputs during the Plio-Pleistocene.

本研究提供了国际海洋发现计划 (IODP) 站点 U1489 的详细沉积地球化学记录，该站点位于巴布亚新几内亚 (PNG) 东北缘附近。围绕硅质碎屑成分的地球化学特征和化学风化程度，利用U1489 上层84 m 共183 个样品重建过去4 Ma 向热带西太平洋的PNG 沉积物供应。我们的地球化学结果显示 U1489 站点沉积物成分的 3 阶段变异性，这与区域构造和气候变化密切相关。阶段 III (~4.0-3.5 Ma) 和 II-A (~2.9-1.7 Ma) 的特征是来自基性岩源的贡献比长英质岩源的贡献更大且可变。这一间隔显示出伴随着相对快速的沉积物输送和更动态的沉积环境，这可能与边缘混合有关，与更频繁的 PNG 构造事件相吻合。特别是，来自超镁铁质/镁铁质岩石的贡献增加记录在~3.5 到 2.9 Ma 之间，这归因于弧-大陆碰撞导致蛇绿岩输入增加。因此，这些结果为 PNG 东部边缘的加速板缝合提供了一致但精确的时间。相比之下，阶段 I (~1.7-0 Ma) 的特征是较细颗粒的背景供应相对恒定，表明化学风化强度随时间持续增加。西太平洋热带地区首次报告了这种增加的风化趋势，它被解释为表明过去的沃克环流加强了~1.7 Ma。总体而言，本文提出的 U1489 站点的硅质碎屑部分的解释为区分上新世-更新世期间构造和气候对 PNG 沉积物输入的影响提供了关键线索。