40Ar/39Ar ages of hornblende grains and bulk Sm/Nd isotopes of circum-Antarctic glacio-marine sediments: Implications for sediment provenance in the southern ocean
- 作者：Martin Roy ; Tina van de Flierdt ; Sidney R. Hemming ; Steven L. Goldstein
- 关键词：Sm– ; Nd isotopes ; 40Ar/39Ar ages ; Sedimentary provenance ; Glacio-marine sediments ; Antarctic geology
- 刊名：Chemical Geology
- 出版年：2007
- 期刊代码：12_00092541
- 类别：ear
- 出版时间：15 October 2007
- 卷：244
- 期：3-4
- 页码：507-519
- 文件大小：1144 K
摘要
The transfer of terrigenous sediments from Antarctica to the Southern Ocean results from glaciological processes and subsequent transport by ocean currents. Establishing the link between the composition of circumpolar sediments and the geology of Antarctica can provide important insights into past ice sheet and ocean current dynamics. Here we document the variability of Antarctic sediment sources using 40Ar/39Ar ages of individual detrital hornblende grains and bulk (< 63 m) Sm/Nd isotope systematics from glacio-marine sediments from 29 cores surrounding Antarctica. High 143Nd/144Nd ratios and associated young Sm/Nd-model ages characterize sediments proximal to West Antarctica, while lower 143Nd/144Nd ratios and correspondingly older Sm/Nd-model ages are found in samples nearby East Antarctica. Detrital hornblende grains in West Antarctic sediments typically have 40Ar/39Ar ages younger than 200 Ma while East Antarctic hornblende grains yield 40Ar/39Ar ages that cluster in a predominant population centered on 
alt="not, vert, similar" border=0> 500 Ma, reflecting the widespread late Neoproterozoic–early Cambrian (Pan-African and Ross) orogenies that affected East Antarctica. An exception comes from sediments adjacent to Wilkes Land, where abundant Mesoproterozoic and Paleoproterozoic hornblende grains suggest that this portion of the East Antarctic craton was largely buffered from Pan-African metamorphism. The geochemical characteristics of sediment sources are thus consistent with the geology of rock outcrops around the Antarctic perimeter. The combined Sm–Nd data and 40Ar/39Ar ages of circum-Antarctic glacio-marine sediments outline several geographic sectors with distinct provenance signals, thereby providing a base map for fingerprinting sediment sources from the Antarctic margin.
alt="not, vert, similar" border=0> 500 Ma, reflecting the widespread late Neoproterozoic–early Cambrian (Pan-African and Ross) orogenies that affected East Antarctica. An exception comes from sediments adjacent to Wilkes Land, where abundant Mesoproterozoic and Paleoproterozoic hornblende grains suggest that this portion of the East Antarctic craton was largely buffered from Pan-African metamorphism. The geochemical characteristics of sediment sources are thus consistent with the geology of rock outcrops around the Antarctic perimeter. The combined Sm–Nd data and 40Ar/39Ar ages of circum-Antarctic glacio-marine sediments outline several geographic sectors with distinct provenance signals, thereby providing a base map for fingerprinting sediment sources from the Antarctic margin.