Detrital zircon provenance and transport pathways of Pleistocene-Holocene eolian sediment in the Pampean Plains, Argentina
Detrital zircon provenance and transport pathways of Pleistocene-Holocene eolian sediment in the Pampean Plains, Argentina
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DOI：
10.1130/b36267.1
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发表时间：
2023-01-01
影响因子：
4.9
通讯作者：
Stubbins, Blake
中科院分区：
文献类型：
--
作者：
Bruner, Austin;Leier, Andrew L.;Stubbins, Blake
阿根廷潘帕斯草原广泛分布着更新世至全新世黄土沉积物和风成沙丘沉积物。描述该风成系统沉积物来源的模型有时会发生冲突。我们通过 U-Pb 碎屑-锆石地质年代学来确定这些矿床的来源。我们的结果表明，样本之间的年龄分布具有广泛的相似性，以二叠纪-三叠纪模式为主，新生代、泥盆纪-密西西比纪、埃迪卡拉纪-寒武纪和中元古代模式也广泛存在但较少。这些数据与之前提出的巴塔哥尼亚碎屑的大量贡献不一致。这些数据与第一周期火山成因锆石对 Pam-pean 风成系统的贡献非常有限相一致，但较老的新近纪锆石的丰度表明安第斯山脉的原始来源。科罗拉多州德萨瓜德罗河和内格罗河的种群可能位于大多数黄土、古土壤和风成沙丘沉积物的尘埃产生路径内，但这些沉积物中锆石年龄的推导不能仅用这些河流系统来解释。一个统计异常值，即来自潘帕地区大西洋海岸的黄土样本，表明与来自科罗拉多河和内格罗河的年龄光谱在数量上相似，这与在全球高冰量下大陆架在地面暴露期间从这些近平行河流系统的推导结果一致。另一个统计异常值是来自巴拉那河三角洲地区的古土壤样本，其锆石年龄与巴拉那地区沉积物的相关性比潘帕地区以南河流的沉积物更密切。总的来说，这些数据表明了潘普亚风成系统的复杂性以及更新世-全新世风成系统中显着的时空变化。
The Pampas of Argentina contain a broad distribution of Pleistocene to Holocene loessic sediments and eolian dune deposits. Models describing the sediment provenance of this eolian system have, at times, conflicted. We address the provenance of these deposits through U-Pb detrital-zircon geochronology. Our results indicate broad similarity in age distributions between samples, with a domi-nant Permian-Triassic mode, and widespread but lesser Cenozoic, Devonian-Mississippian, Ediacaran-Cambrian, and Mesoproterozoic modes. These data are inconsistent with a large contribution of detritus from Patago-nia as previously suggested. These data are consistent with very limited contribution of first cycle volcanogenic zircon to the Pam-pean eolian system, but abundances of older Neogene zircon indicate proto-sources in the Andes. The rios Desaguadero, Colorado, and Negro contain populations that were likely within the dust production pathways of most of the loess, paleosol, and eolian dune depos-its, but the derivation of the zircon ages in these sediments cannot be explained solely by these river systems. One statistical out-lier, a loess sample from the Atlantic coast of the Pampa region, indicates quantitative similarity to the age spectra from the rios Colorado and Negro, consistent with deri-vation from these subparallel rivers systems during subaerial exposure of the continental shelf under high global ice-volume. Another statistical outlier, a paleosol sample from the Rio Parana delta region, has zircon ages more closely associated with sediments in the Parana region than in rivers south of the Pampa region. Collectively, these data point to the complexity of the Pampean eolian system and substantial spatial-temporal variation in this Pleistocene-Holocene eolian system.