Nd bulk isotopes and 40Ar/39Ar ages of individual minerals from Aurora and Wilkes sub-glacial basin sediments@en

The Wilkes and Aurora basins are large, low-lying sub-glacial basins that may cause areas of weakness in the overlying East Antarctic ice sheet. Previous work based on ice-rafted debris (IRD) provenance analyses found evidence for massive iceberg discharges from these areas during the late Miocene and Pliocene. Here we characterize the sediments shed from the inferred areas of weakness along this margin (94°E to 165°E) by measuring40Ar/39Ar ages of 292 individual detrital hornblende grains from eight marine sediment core locations off East Antarctica and Nd isotopic compositions of the bulk fine fraction from the same sediments. We further expand the toolbox for Antarctic IRD provenance analyses by exploring the application of 40Ar/39Ar ages of detrital biotites; biotite as an IRD tracer eliminates lithological biases imposed by only analyzing hornblendes and allows for characterization of samples with low IRD concentrations. Our data quadruples the number of detrital 40Ar/39Ar ages from this margin of East Antarctica and leads to the following conclusions: (1) Four main sectors between the Ross Sea and Prydz Bay, separated by ice drainage divides, are distinguishable based upon the combination of 40Ar/39Ar ages of detrital hornblende and biotite grains and the e-Nd of the bulk fine fraction; (2) 40Ar/39Ar biotite ages can be used as a robust provenance tracer for this part of East Antarctica; and (3) sediments shed from the coastal areas of the Aurora and Wilkes sub-glacial basins can be clearly distinguished from one another based upon their isotopic fingerprints.威尔克斯盆地与奥罗拉盆地（Wilkes and Aurora basins）是大型低洼冰下盆地，可能对上覆的东南极冰盖造成薄弱区域。此前基于冰筏碎屑（ice-rafted debris, IRD）物源分析的相关研究，已获取到中新世晚期至上新世期间，上述区域发生大规模冰山崩解的证据。本研究针对该冰缘带（东经94°至165°）的推测薄弱区域产出的沉积物，通过对东南极近海8个海洋沉积岩芯站位的292颗单个碎屑角闪石开展40Ar/39Ar年代学测试，以及对同批次沉积物的细粒全组分进行钕同位素组成分析，完成了其物源特征刻画。本研究进一步拓展了南极冰筏碎屑物源分析的方法体系：探索了碎屑黑云母40Ar/39Ar年代学的应用场景——以黑云母作为冰筏碎屑示踪剂，可消除仅针对角闪石分析所引入的岩性偏倚，同时能够对冰筏碎屑浓度较低的样品实现物源刻画。本研究获得的数据将东南极该冰缘带的碎屑40Ar/39Ar年代学样本量提升至此前的四倍，并得到以下三点结论：（1）罗斯海与普里兹湾之间存在四个以冰水分水岭为界的主要物源分区，可通过碎屑角闪石、黑云母的40Ar/39Ar年代学特征与细粒全组分的εNd值组合加以区分；（2）黑云母40Ar/39Ar年代学可作为东南极该区域可靠的物源示踪工具；（3）奥罗拉与威尔克斯冰下盆地沿岸区域产出的沉积物，可通过其同位素指纹特征实现清晰区分。