Deciphering seasonal to decadal climate variability during the Oligocene: an integrated approach based on bivalve sclerochronology and palynology

地球历史上最后一次以单极冰川作用为特征，随后两极冰盖显著减少是在渐新世期间。因此，渐新世世界可以作为未来气候边界条件的化石模拟，其最初特征是北方冰盖的丧失。由此产生的气候变化将包括季节性的变化以及十年气候振荡的频率和强度。然而，这些变化的方式和克里思还没有受到很好的限制。鉴于上述情况，我们的联合项目将重建短期气候动态在中欧在渐新世后结合sclerochronous和孢粉学的方法。我们将重点关注美因茨和卡塞尔盆地的浅海演替，这两个盆地都有保存完好的双壳类（包括寿命极长的物种）和孢粉形生物。软体动物壳的生长模式和同位素地球化学将为渐新世气候打开长达一个世纪的窗口，并提供有关季节性至十年期气候振荡的连贯数据。除了产生年龄控制，dinocysts和孢子虫将允许（定性和定量）重建海洋和陆地环境的古环境参数。具体而言，该项目将解决渐新世期间东北大西洋部分海洋和大气气候模式的频率和强度、温度趋势以及降水事件的相对强度和持续时间等问题。此外，我们将研究冷水软体动物数量增加、多样性低和某些地层中贝壳厚度异常的原因。

The last time in Earth history characterized by a unipolar glaciation followed by a significant reduction of polar ice sheets was during the Oligocene. Hence, the Oligocene world may serve as a fossil analog for the climatic boundary conditions of the future, which will be initially characterized by a loss of Northern Hemisphere ice sheets. The resulting climate shifts will include changes in seasonality as well as in the frequency and intensity of decadal climate oscillations. However, the mode and tempo of these changes are as yet poorly constrained. In light of the above, our joint project will reconstruct short-term climate dynamics in Central Europe during the Oligocene following a combined sclerochronological and palynological approach. We will focus on shallow marine successions from the Mainz and Kassel Basins, which yield both excellently preserved bivalves (including extremely long-lived species) and palynomorphs. The growth patterns and isotope geochemistry of mollusk shells will open century-long windows into the Oligocene climate and provide coherent data on seasonal to decadal climate oscillations. Besides yielding age control, dinocysts and sporomorphs will allow to (qualitatively and quantitatively) reconstruct paleoenvironmental parameters for marine and terrestrial settings. Specifically, the project will address questions on the frequency and intensity of oceanic and atmospheric climate modes, temperature trends, and the relative strength and duration of precipitation events in the NE Atlantic sector during the Oligocene. Furthermore, we will study the reasons for the increased amounts of cold-water mollusks, low diversity and extraordinary thickness of shells in certain stratigraphic levels.