Plio-pleistocene marine paleoenvironments and dinoflagellate cyst paleoecology

对北大西洋和邻近海域过去4.9百万年的高纬度环境进行数值重建是这项提议的主要目标。因此，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。有机壁甲藻包囊，或称“甲藻包囊”，现在经常被用于定量重建晚期第四纪海洋环境，特别是在高纬度地区，那里的钙质微化石组合多样性下降。通过对其化石记录的分析，我们可以从数值上重建夏季和冬季海面温度和盐度、海冰覆盖时间和营养丰富程度。然而，使用甲藻包囊重建许多早期的第四纪和上新世环境，受到灭绝物种和特殊物种组合的增加的阻碍。挑战是理解这些老组合的环境意义，从而向后延伸甲藻在环境定量分析中的作用。这项拟议的研究以非常高的分辨率研究了上新世和更新世具有关键古气候意义的六个时间间隔(每个时间间隔约为100KYR或更短)的恐囊。将基于现有的深海岩心材料，从整个北大西洋地区检查这些材料。这些组合将通过获得稳定的同位素和镁/钙比作为完全独立的气候变化指标进行唯一校准，并能够精确调整到轨道时间尺度。其目的是对上新世-更新世恐囊生态有一个定量的了解，并将其应用于了解更多有关的时间间隔。这些结果将解决晚新生代气候、气候和气候的动力学问题。特别是在高纬度地区，海冰复盖和季节性的恐囊重建将为北半球冰川形成的时间和原因提供新的见解。这些结果将与古气候建模和地层学相关，特别是在高纬度地区，那里的矿化微化石群多样性较低。

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.