Relative sea-level variability during the late Middle Pleistocene: New evidence from eastern England
Relative sea-level variability during the late Middle Pleistocene: New evidence from eastern England
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DOI：
10.1016/j.quascirev.2017.08.017
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发表时间：
2017-10
影响因子：
4
通讯作者：
N. Barlow;A. Long;W. Gehrels;M. Saher;R. Scaife;H. Davies;K. Penkman;D. Bridgland;A. Sparkes-A.-Spar
中科院分区：
文献类型：
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作者：
N. Barlow;A. Long;W. Gehrels;M. Saher;R. Scaife;H. Davies;K. Penkman;D. Bridgland;A. Sparkes-A.-Spar
揭开以往间冰期期间相对海平面变化的模式，增强了我们对冰盖对气候变化的反应的理解。温带河口环境有可能保存以前间冰期（温暖）时期的相对海平面的连续记录。这一点很重要，因为目前，我们通常只有低纬度珊瑚的海平面高水位快照和升高的古海岸线指标，而（连续的）深海氧同位素记录只能提供海平面变化的间接证据。在这里，我们专注于在英格兰东部的纳尔山谷，在其中保存的证据晚中更新世海侵超过20米的垂直范围。通过应用模型的海岸演替和海平面的趋势，在全新世海平面的研究中使用的，我们评估的模式（突然与渐进）的海平面变化记录的间冰期纳尔谷序列。编译古地层证据，包括有孔虫，花粉和氨基酸外消旋测年，表明在纳尔谷间冰期序列的海平面变化的模式是渐进的，可能有两个阶段的区域海侵和相对海平面上升发生在两个不同的时间。第一阶段发生在海洋氧同位素阶段（MIS）11的后期，从0.18到18 m OD;第二阶段可能发生在MIS 9的早期，从0.03到3 m OD（这些估计包括长期构造抬升）。我们不能最终排除替代MIS 11年龄为这些较低的沉积物。缺乏纳尔河谷海平面快速波动的指标，增加了MIS 11和MIS 9期间冰盖稳定融化的论点的份量。
Unravelling patterns of relative sea-level change during previous interglacials enhances our understanding of ice sheet response to changing climate. Temperate-latitude estuarine environments have the potential to preserve continuous records of relative sea level from previous interglacial (warm) periods. This is important because, currently, we typically only have snapshots of sea-level highstands from low-latitude corals and raised palaeoshoreline indicators while the (continuous) deep-sea oxygen isotope record only provides indirect evidence of sea-level changes. Here, we focus on the Nar Valley in eastern England, in which is preserved evidence of a late middle-Pleistocene marine transgression more than 20 vertical metres in extent. By applying a model of coastal succession and sea-level tendencies, as used in Holocene sea-level studies, we assess the mode (abrupt versus gradual) of sea-level change recorded by the interglacial Nar Valley sequences. Compiled palaeo-stratigraphic evidence comprising foraminifera, pollen and amino acid racemization dating, suggests that the mode of sea-level change in the Nar Valley interglacial sequence was gradual, with potentially two phases of regional transgression and relative sea-level rise occurring at two separate times. The first phase occurred during the latter part of marine Oxygen Isotope Stage (MIS) 11 from ∼8 to 18 m OD; and, the second phase potentially occurred during early MIS 9 from ∼-3 to 3 m OD (with long-term tectonic uplift included in these estimates). We cannot conclusively preclude an alternative MIS 11 age for these lower sediments. The lack of indicators for rapid sea-level oscillations in the Nar Valley adds weight to an argument for steady melt of the ice sheets during both MIS 11 and 9.