Sediments transported in rivers reflect the geology of the catchment area and its radiogenic isotopic composition. These isotopic signatures are not significantly altered by weathering, transport or deposition and hence can document variations in sediment supply. Here we present strontium (Sr), neodymium (Nd) and lead (Pb) isotope values from suspended and riverbed sediments of the Plata River drainage basin, the second largest on the South American continent, and from two marine sediment cores collected off the mouth of the Plata River in the western subtropical South Atlantic. Our modern riverine data suggest that the basin has three main sediment source areas, namely the upper Paraná River, the Uruguay River and the Andean draining rivers. Sediments from the Andean draining rivers (Salado and Bermejo Rivers) have the most radiogenic Pb (i.e. >18.5 for ²⁰⁶Pb/²⁰⁴Pb) and Sr (average of 0.726 ± 0.031; 2SD) isotopic signatures, and least radiogenic ε_Nd values (average of −10.5 ± 3.1; 2SD). The upper Paraná and Uruguay Rivers have less radiogenic Pb (i.e. <18.5 for ²⁰⁶Pb/²⁰⁴Pb) and Sr (average of 0.715 ± 0.003; 2SD) isotopic signatures. While the upper Paraná River has average ε_Nd values of −7.8 ± 1.1 (2SD), the Uruguay River has average ε_Nd values of −5.9 ± 0.2 (2SD). The modern isotopic signature at the mouth of the Plata River is largely dominated by the Andean draining rivers. To reconstruct changes in sediment supply to the western subtropical South Atlantic, we used this new riverine dataset together with literature values from the Argentine continental margin to interpret the data from two marine sediment cores. The downcore records cover the last ∼30 kyr and show two short-lived excursions (i.e. Heinrich Stadial 1 and the Younger Dryas) and two long-term trends (i.e. late Pleistocene (i.e. ∼29 to 11 cal ka BP for Sr and ∼29 to 25 cal ka BP for Nd), and early and mid-Holocene). We suggest that the short-lived excursions result from increased precipitation in the headlands of the Andean draining rivers during Heinrich Stadial 1 and the Younger Dryas. The late Pleistocene long-term change showed an increase in the contribution of material from the Plata River drainage basin in relation to material from the Argentine continental margin most probably due to low sea-level. The early and mid-Holocene long-term trend showed the opposite change in sediment input and was related to decreased precipitation over most of the Plata River drainage basin.

河流中沉积的沉积物反映了集水区的地质及其放射性同位素组成。这些同位素特征不会因风化，运输或沉积而显着改变，因此可以记录沉积物供应量的变化。在这里，我们介绍了南美大陆第二大的普拉塔河流域的悬浮和河床沉积物中的锶（Sr），钕（Nd）和铅（Pb）同位素值，以及从口中收集的两个海洋沉积物核心西亚热带南大西洋的普拉塔河河。我们的现代河流数据表明，该盆地有三个主要的泥沙源区，即上巴拉那河，乌拉圭河和安第斯流域河流。来自安第斯山脉排水河（Salado和Bermejo河）的沉积物中放射性最高的Pb（即²⁰⁶的Pb / ²⁰⁴ Pb）的和Sr（平均0.726±0.031; 2SD）同位素签名，以及至少放射ε_的Nd的值（平均-10.5±3.1; 2SD）。巴拉那河和乌拉圭河上游的放射性同位素较少（即²⁰⁶ Pb / ²⁰⁴ Pb <18.5 ）和Sr（平均值为0.715±0.003； 2SD）同位素特征。而上巴拉那河具有平均ε_钕-7.8±1.1（2SD）的值，乌拉圭河具有平均ε_钕值为-5.9±0.2（2SD）。普拉塔河河口的现代同位素特征主要由安第斯流域河流控制。为了重建西亚热带南大西洋沉积物供应的变化，我们使用了这个新的河流数据集以及阿根廷大陆边缘的文献值来解释来自两个海洋沉积物核心的数据。下游记录涵盖了最后的约30年，并显示了两次短期旅行（即Heinrich Stadial 1和Younger Dryas）和两个长期趋势（即晚更新世（即Sr的约29到11 cal ka BP，约29 bp）到25 cal ka BP（Nd），以及全新世早期和中期）。我们建议短期旅行是由于海因里希体育场1和年轻树妖在安第斯流域河流的岬角降水增加所致。晚更新世的长期变化表明，相对于阿根廷大陆边缘的物质而言，普拉塔河流域的物质贡献有所增加，这很可能是由于海平面较低所致。全新世早期和中期的长期趋势显示出泥沙输入的相反变化，并且与大部分普拉塔河流域的降水减少有关。