Plio-pleistocene marine paleoenvironments and dinoflagellate cyst paleoecology

在过去的490万年北大西洋和邻近海域的高纬度环境的数值重建是这个建议的一个主要目标。 这种重建对于理解海洋气候系统和验证计算机气候模拟至关重要。有机壁甲藻孢囊，或“dinocysts”，现在经常用于定量重建晚第四纪海洋环境，特别是在高纬度地区的钙质微体化石组合的多样性下降。 对它们的化石记录的分析使我们能够在数值上重建夏季和冬季的海面温度和盐度、海冰覆盖的持续时间和营养物质富集的水平。 然而，使用dinocysts重建许多更早的第四纪和上新世环境受到越来越多的灭绝物种和不寻常的物种协会的存在。 面临的挑战是要了解这些老组合的环境意义，从而向后延伸的时间的实用性，定量环境分析的dinocysts。拟议的研究在上新世和更新世的关键古气候兴趣的六个时间间隔（每个约100 kyr持续时间或更短）非常高的分辨率检查dinocysts。 将根据现有的深海岩心材料，对整个北大西洋区域的材料进行审查。 通过获得稳定的同位素和Mg/Ca比率，将对组合进行独特的校准，以作为气候变化的完全独立的代理，并允许精确调整到轨道时间尺度。 其目的是发展上新世更新世dinocyst生态学的定量理解，并应用此来了解更多有关的时间间隔问题。 结果解决晚新生代气候的动态，特别是在高纬度地区的海冰覆盖和季节性的dinocyst重建将提供新的见解的时间和原因的北方半球冰川。 研究结果将与古气候建模和地层学有关，特别是在高纬度地区，矿化微体化石群的多样性较低。

Numerical reconstructions of high-latitude environments in the North Atlantic and adjacent seas during the past 4.9 Myr are a major aim of this proposal.  Such reconstructions are critical for understanding the ocean-climate system and validating computer climate simulations. Organic-walled dinoflagellate cysts, or "dinocysts", are now used frequently in quantitative reconstructions of later Quaternary marine environments, especially at higher latitudes where calcareous microfossil assemblages decline in diversity.  The analysis of their fossil record allows us to reconstruct numerically both summer and winter sea-surface temperature and salinity, the duration of sea-ice cover, and levels of nutrient enrichment.  However, using dinocysts to reconstruct many earlier Quaternary and Pliocene environments is hindered by the increasing presence of extinct species and unusual species associations.  The challenge is to understand the environmental significance of these older assemblages, thereby extending backwards in time the utility of dinocysts for quantitative environmental analysis. The proposed research examines dinocysts at very high resolution across six time intervals (each about 100 kyr duration or less) of critical paleoclimatic interest for the Pliocene and Pleistocene.  Material will be examined from across the North Atlantic region, based on existing deep-sea core material.  Assemblages will be uniquely calibrated throughout by obtaining stable isotopes and Mg/Ca ratios to serve as fully independent proxies for climate change, and allow precise tuning to an orbital timescale.  The aim is to develop a quantitative understanding of Plio-Pleistocene dinocyst ecology, and to apply this to learn more about the time intervals in question.  Results address the dynamics of late Cenozoic climate, especially at higher latitudes where dinocyst reconstructions of sea-ice cover and seasonality will provide new insights into the timing and causes of Northern Hemisphere glaciations.  Results will be relevant to paleoclimate modeling and stratigraphy especially at high latitudes where mineralized microfossil groups are of low diversity.