Glacial erosion of East Antarctica in the Pliocene: A comparative study of multiple marine sediment provenance tracers
Glacial erosion of East Antarctica in the Pliocene: A comparative study of multiple marine sediment provenance tracers
复制标题
DOI：
10.1016/j.chemgeo.2017.06.011
复制
发表时间：
2017-09
期刊：
影响因子：
3.9
通讯作者：
C. Cook;S. Hemming;T. Flierdt;Elizabeth Pierce Davis;T. Williams;A. L. Galindo;F. Jiménez-Espejo;C. Escutia
中科院分区：
文献类型：
--
作者：
C. Cook;S. Hemming;T. Flierdt;Elizabeth Pierce Davis;T. Williams;A. L. Galindo;F. Jiménez-Espejo;C. Escutia
南极东部冰盖的历史为了解其在全球变暖中的潜在未来行为提供了重要的依据。如果被冰原侵蚀的下垫大陆是由不同的地质地体构成的，这些地质地体可以通过被侵蚀沉积物的矿物学、岩石学和/或地球化学来区分，那么冰川海洋沉积物的来源可以提供对这段历史的深入了解。本文对位于东南极洲Wilkes冰下盆地近海的综合海洋钻探计划（IODP） U1361站点的上新世沉积物进行了多代理物源调查。对比了< 63 μm碎屑组分的Nd和Sr同位素组成、< 2 μm碎屑组分的粘土矿物学特征、> ~ 150 μm冰封角辉石颗粒的40Ar/39Ar年龄、> ~ 2 mm冰封碎屑和> ~ 150 μm矿物颗粒的岩石学特征。上新世细粒海相沉积物具有Nd和Sr同位素组成、粘土矿物学和碎屑特征，这些特征可以用主要来自近端结晶地体的侵蚀沉积物与来自目前冰川覆盖的威尔克斯冰下盆地的内陆物质的混合来解释。相反，这种内陆来源的证据在冰载角闪岩年代中是缺失的。我们认为，在盆地内的碎屑岩和沉积单元中，对角闪石颗粒的岩性偏向是对这一观察结果最可能的解释。然而，40Ar/39Ar角斑岩年龄记录了来自罗斯海远端边缘的额外物源，甚至可能来自Marie Byrd Land的南极西部地区。后者位于东部约2000公里处，暗示着在上新世温暖期，南极西部冰盖有大量冰山释放。总之，我们的结果为结合粗粒和细粒冰川海洋沉积物组分的地球化学和矿物学特征提供了强有力的案例，以便在冰雪覆盖地区获得可靠的物源解释。
The history of the East Antarctic ice sheet provides important understanding of its potential future behaviour in a warming world. The provenance of glaciomarine sediments can provide insights into this history, if the underlying continent eroded by the ice sheet is made of distinct geological terranes that can be distinguished by the mineralogy, petrology and/or geochemistry of the eroded sediment. We here present a multi-proxy provenance investigation on Pliocene sediments from Integrated Ocean Drilling Program (IODP) Site U1361, located offshore of the Wilkes Subglacial Basin, East Antarctica. We compare Nd and Sr isotopic compositions of < 63 μm detrital fractions, clay mineralogy of < 2 μm fractions,40Ar/39Ar ages of > 150 μm ice-rafted hornblende grains, and petrography of > 2 mm ice-rafted clasts and > 150 μm mineral grains. Pliocene fine-grained marine sediments have Nd and Sr isotopic compositions, clay mineralogy, and clast characteristics that can be explained by mixing of sediments eroded from predominantly proximal crystalline terranes with material derived from inland sources from within the currently glaciated Wilkes Subglacial Basin. Conversely, evidence for such an inland source is absent from ice-rafted hornblende ages. We render a lithological bias against hornblende grains in the doleritic and sedimentary units within the basin the most likely explanation for this observation.40Ar/39Ar hornblende ages however record additional provenance from the distal margins of the Ross Sea, and possibly even the West Antarctic area of Marie Byrd Land. The latter lies > 2000 km to the east and hints at significant iceberg release from the West Antarctic ice sheet during warm intervals of the Pliocene. Together our results make a strong case for combining geochemical and mineralogical signatures of coarse- and fine-grained glaciomarine sediment fractions in order to derive robust provenance interpretations in ice covered areas.