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的极地冰盖显着减少是在渐新世。因此，渐新世可能是未来气候边界条件的化石类比，其最初的特征将是北半球冰盖的丧失。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的变化。然而，这些变化的模式和节奏迄今还没有得到很好的约束。有鉴于此，我们的联合项目将采用硬化学和孢粉学相结合的方法，重建渐新世期间中欧的短期气候动态。我们将专注于美因茨和卡塞尔盆地的浅海序列，那里既有保存完好的双壳类(包括极其长寿的物种)，也有孢粉类。双壳类贝壳(生长模式，δ18O，δ13C，锶/钙)将打开进入渐新世气候的长达一个世纪的窗口，并提供关于季节到年代际气候振荡的连贯数据。除了产生年龄控制外，藻囊和孢子体将允许(定性和定量)重建海洋和陆地环境的古环境参数。具体而言，该项目将讨论海洋和大气气候模式的频率和强度、温度趋势以及渐新世期间东北大西洋地区降水事件的相对强度和持续时间等问题。此外，我们还将研究某些地层中冷水软体动物数量增加、多样性低和贝壳厚度超常的原因。

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. Bivalve shells (growth patterns, δ18O, δ13C, Sr/Ca) of 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.