A long-term neodymium isotope (εNd) record of fossil fish teeth was investigated to constrain the evolution of deep-water circulation in the abyssal South China Sea (SCS) during the late Oligocene–Miocene (27–10 Ma). Fish teeth samples were collected from the oceanic red beds at International Ocean Discovery Program Expedition 367 Site U1499 (water depth 3758 m). Seawater εNd values (from –7.1 to –4.8, average –6.1) prior to 15 Ma indicate that water masses in the abyssal SCS resulted from the mixing of more radiogenic Upper Circumpolar Deep Water (UCDW, average –4.5) and less radiogenic Lower Circumpolar Deep Water (LCDW, average –6.4). The general decrease in εNd values was attributed to an increasing influence of the unradiogenic LCDW at the studied site, consistent with the subsidence and the associated deepening of the SCS plain. After 15 Ma, seawater εNd dropped significantly to a range of –8.9 to –6.1 (average –7.5), indicating a slowdown in the hydrological connection between the deep-water masses in the SCS and the western Pacific Ocean. We argue that the formation of the Luzon Strait due to the uplift of the Luzon arc in the late Miocene led to the shallowing and narrowing of the SCS-Pacific channels. Consequently, penetration of LCDW was reduced and water masses in the abyssal SCS would have been less ventilated and strongly influenced by lithogenic input from the unradiogenic sediments of large Asian rivers draining the peri-Himalayan region.

中文翻译：

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南海深海深水环流晚渐新世-中新世演化：来自鱼牙化石Nd同位素的见解


研究了鱼牙化石的长期钕同位素（εNd）记录，以限制渐新世晚期至中新世（27-10 Ma）南海深水环流的演化。鱼牙样本采集自国际海洋发现计划探险367站点U1499（水深3758 m）的海洋红床。 15 Ma之前的海水εNd值（从–7.1到–4.8，平均–6.1）表明，南海深海水团是由放射源较多的上绕极深水（UCDW，平均–4.5）和放射源较少的下绕极深水混合而成的。深水（LCDW，平均值 –6.4）。 εNd 值的普遍下降归因于研究地点非放射性 LCDW 的影响不断增加，这与南海平原的沉降和相关加深一致。 15 Ma后，海水εNd显着下降至–8.9至–6.1（平均–7.5），表明南海深水团与西太平洋之间的水文联系放缓。我们认为，中新世晚期吕宋岛弧隆起导致吕宋海峡的形成，导致南海-太平洋航道变浅和变窄。因此，LCDW 的渗透减少，南海深海水团的通风较差，并受到流向喜马拉雅山周边地区的亚洲大河非放射性沉积物的强烈影响。