Evolution of Sea Surface Temperatures in the Coastal Antarctic Paleoenvironment During the Late Cretaceous and Paleogene

该奖项由极地项目办公室的南极地质和地球物理项目提供，支持建立白垩纪晚期和古近纪早期气候长期记录的研究，以评估南极洲沿海边缘温度的年度季节性。在西摩岛收集的保存完好的双壳类贝壳的稳定同位素和元素组成将成为重建古环境条件的主要数据来源。通过沿着双壳生长结构的高分辨率采样收集的季节温度记录将允许评估不同气候状态和快速气候变化时期的季节性。此外，高地层分辨率将使该项目能够探测到可能延伸到如此高纬度地区的短暂热偏移的存在和频率。为了编制可靠的古气候时间记录，将采取两种主要的调查途径：1)通过使用几何投影的图形技术，在一个大的地理区域内对化石进行精确的地层（因此，时间）放置；2)进行稳定同位素和元素分析，推导古温度，评价壳物质的成岩蚀变。为了提供跨地层层位古温度的真实比较，本研究将侧重于单个分类单元，从而避免了由于该地区以前研究中遇到的动物组合混合而导致的复杂性。Seymour岛的近岸海洋化石记录为解决南极古环境的诸多问题提供了独特的机会，包括季节性与不同气候状态的关系、气候对特定分类群生物地理分布的影响、晚白垩世至始新世冰体积变化对稳定同位素记录的影响，以及这段时间内高纬度底水形成的可行性。特别是，将收集到的有关季节性模式和短时间热漂移存在（或不存在）的信息，对于了解高纬度地点在气候从全球寒冷条件向全球温暖条件转变期间的响应将非常有价值。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports research for construction of a long-term record of climate during the late Cretaceous and early Paleogene to assess the annual seasonality in temperature on the coastal margin of Antarctica. Stable isotope and element compositions of well-preserved bivalve shells collected on Seymour Island will be the primary source of data used to reconstruct paleoenvironmental conditions. Seasonal temperature records collected through high-resolution sampling along growth structures in bivalve shells will allow seasonality to be assessed during different climate states and during periods of rapid climate change. In addition, high stratigraphic resolution will enable this project to detect the presence and frequency of short-lived thermal excursions that may have extended to such high latitudes.To compile a reliable temporal record of paleoclimate, two major avenues of investigation will be undertaken: 1) precise stratigraphic (and therefore, temporal) placement of fossils over a large geographic area will be employed through the use of a graphical technique employing geometric projections; 2) stable isotope and elemental analyses will be performed to derive paleotemperatures and to evaluate diagenetic alteration of shell materials. To provide realistic comparisons of paleotemperatures across stratigraphic horizons, this study will focus on a single taxon, thus avoiding complications due to the mixing of faunal assemblages that have been encountered in previous studies of this region.The near-shore marine fossil record on Seymour Island provides a unique opportunity to address many questions about the Antarctic paleoenvironment, including the relation between seasonality and different climate states, the influence of climate on biogeographic distribution of specific taxa, the effect of ice-volume changes on the stable isotope record from the late Cretaceous through the Eocene, and the plausibility of high-latitude bottom water formation during this time interval. In particular, information that will be collected concerning patterns of seasonality and the presence (or absence) of short-lived thermal excursions will be extremely valuable to an understanding of the response of high latitude sites during climate transitions from globally cool to globally warm conditions.