Impact of Eocene‐Oligocene Antarctic Glaciation on the Paleoceanography of the Weddell Sea
Impact of Eocene‐Oligocene Antarctic Glaciation on the Paleoceanography of the Weddell Sea
复制标题
DOI：
10.1029/2022pa004440
复制
发表时间：
2022-12
影响因子：
3.5
通讯作者：
Victoria Hojnacki;A. Lepp;Josie Horowitz Castaldo;Abbey States;Xiaona Li;S. Passchier
中科院分区：
文献类型：
--
作者：
Victoria Hojnacki;A. Lepp;Josie Horowitz Castaldo;Abbey States;Xiaona Li;S. Passchier
始新世-渐新世过渡（EOT）在~ 34 Ma标志着气候从温室到冰窖条件的转变，朝着持续较低的全球温度和南极大陆冰盖的方向转变。我们报告了大西洋环流南极分支威德尔海海洋钻探计划（ODP） 696站点EOT的沉积学和无机地球化学结果。碎屑的地球化学组成、自生和生物成因的海洋沉积物组分以及可分选的粉砂代用物显示了冰生长对高纬度水团的影响。可选粉砂粒度和Zr/Rb比值表明在~ 36.2 ~ 35.8 Ma期间存在强烈环流，与已知的南大洋暖期一致。在整个东第三纪，碎屑物源表明，威德尔海西部的区域冰是逐步增长的，首先在南极半岛扩张，其次是南极洲西部的部分地区。结合区域冰的生长，跨EOT段沉积物中的高铀富集因子（U EF）表明沉积物中存在缺氧条件，并有碳酸盐溶解的证据。在~ 33.6 Ma的冰川膨胀和海冰形成之后，观察到恢复到氧条件和碳酸盐保存，过量的钡和磷表明生产力增加，并可能产生碳输出。我们的研究结果强调了冰的增长与EOT高纬度水团变化特性之间的重要联系，以及对全球海洋环流的影响。
The Eocene‐Oligocene Transition (EOT) at ∼34 Ma marked a climatic shift from greenhouse to icehouse conditions, toward long‐lasting lower global temperatures and a continental ice sheet in the Antarctic. We report on sedimentological and inorganic geochemical results across the EOT at Ocean Drilling Program (ODP) Site 696 in the Weddell Sea, within the Antarctic limb of the Atlantic circulation. The geochemical composition of detrital, authigenic and biogenic marine sediment components, and sortable silt proxies demonstrate the impact of ice growth on high latitude water masses. Sortable silt grain size and Zr/Rb ratios attest to a period of vigorous circulation at ∼36.2–35.8 Ma, coincident with a known warm interval in the Southern Ocean. Across the EOT, detrital provenance suggests that regional ice growth in the western Weddell Sea was stepwise, first expanding in the Antarctic Peninsula, followed by parts of West Antarctica. In conjunction with regional ice growth, high uranium enrichment factors (U EF) in sediments spanning the EOT interval indicate anoxic conditions in the sediment with evidence of carbonate dissolution. Following glacial expansion and sea‐ice formation at ∼33.6 Ma, a return to oxic conditions and carbonate preservation is observed with excess barium and phosphorous indicative of an increase in productivity, and potentially carbon export. Our results highlight the important connections between ice growth and the changing properties of high‐latitude water masses at the EOT with impacts on the global ocean circulation.