Marine and terrestrial records of Toarcian (Early Jurassic) climate and environmental change - Phase 2: Evolution of Early Jurassic Environment in NE-Germany

在该项目的第一阶段，我们调查了Pliensbachian/Toarcian和Toarcian环境危机期间的环境扰动，制定了三个待检验的假设，所有这些假设都可以被证明。1)托阿尔期的变暖与大陆冰冻圈的消亡有关。冰的融化影响了特提斯陆架水的δ 18 O值，并掩盖了储存在生物钙化器中的氧同位素温度信号。独立的证据是通过建立一个古温度记录的基础上冰体积独立的分子古温度计使用TEX-86代理。2)我们假设，Pliensbachian和早期Toarcian气候事件同样影响陆地以及海洋环境，证明了海洋和陆源光合作用的同位素特征的调查。3)海洋初级生产者社区直接受到海水温度上升和大气中二氧化碳浓度上升造成的海洋酸化的影响。利用卢森堡多阿克期沉积物中的三萜类生物标志化合物，识别出6个反映早多阿克期初级生产者群落（红色与绿色分支）变化的生物事件，旨在从时空两个方面拓展早侏罗世古环境演化的研究目标。优先在具有“沥青相”的缺氧/缺氧盆地中进行关于Pliensbachian/Toarcian环境变化的调查。在这些基础上，严重的氧气消耗影响了碳循环，并提供了一个分离的第一阶全球驱动程序从第二阶区域驱动程序。非沥青段，特别是从北冈瓦纳边缘和伊比利亚半岛的碳酸盐台地上开发缺乏连续的沉积和详细的记录的环境变化的分子和同位素组成的有机物质是难以实现的，由于不稳定的沉积/侵蚀和降解的有机物在含氧环境。我们建议研究早侏罗世的环境变化，在东北德国盆地，沉积物沉积在一个连续的和地层约束良好的边缘盆地的Toarcian货架不受严重缺氧和沥青相的发展。通过分子生物标志物和同位素地球化学研究，可以确定全球pCO 2和碳同位素的一级驱动因子。我们将遵循整个继承Rhaetian Aalenian古环境变化，采用两个核心，在东北-德国盆地，以前没有研究，并将建立一个化学地层和生物地层框架的解释早侏罗世古环境变化超过一段时间的30马最终在Toarcian海洋缺氧事件。

In the first phase of this project, we investigated environmental perturbations during the Pliensbachian/Toarcian and Toarcian environmental crisis formulating three hypothesis to be tested, all of which could be proven. 1) Toarcian warming was associated with a demise of a continental cryosphere. Ice melting impacted on 18O values of Tethyan shelf water and obscured the oxygen isotope temperature signal stored in biocalcifiers. Independent proof was achieved by establishment of a paleotemperature record based on ice volume-independent molecular paleothermometry using the TEX-86 proxy. 2) We postulated that Pliensbachian and early Toarcian climate events equally affected terrestrial as well as marine environments, proven by investigation of isotopic signatures in marine and terrigenous photosynthate. 3) Marine primary producer communities directly suffered from rising seawater temperatures and ocean acidification via rising atmospheric CO2 concentration. We identified six biotic events reflecting changes in primary producer associations (red versus green clades) in the Early Toarcian using triterpenoidal biomarker compositions of Toarcian sediments from Luxembourg.We now aim to extend the research on early Jurassic paleoenvironment evolution by extending the study objectives in both the spatial and temporal domain. Investigations addressing Pliensbachian/Toarcian environmental change were preferentially conducted in anoxic/euxinic basins with “bituminous facies”. Severe oxygen depletion affected carbon cycling in those basis and affords a separation of first-order global drivers from second-order regional drivers. Non-bituminous sections, particularly from the north Gondwana margin and Ibera that developed on carbonate platforms lack continuous sedimentation and a detailed record of environment change in the molecular and isotopic composition of organic material is difficult to achieve, due to erratic sedimentation/erosion and degradation of organics in oxygenated environments. We propose to study early Jurassic environmental change in the NE-German Basin, where sediments were deposited in a continuous and stratigraphically well-constrained marginal basin of the Toarcian shelf not subject to severe anoxia and development of bituminous facies. First order global drivers on pCO2 and carbon isotopes can thus be identified by means of molecular biomarker and isotope geochemistry.The Toarcian paleoenvironmental evolution occurred in the wake of the Gondwana break-up initiated by CAMP volcanism some 200 Ma ago. We will follow the entire succession of Rhaetian to Aalenian paleoenvironmental change employing two cores available in the NE-German Basin that have not been studied previously and will establish a chemostratigraphic and biostratigraphic framework for interpretation of early Jurassic paleoenvironmental change over a period of 30 Ma culminating in the Toarcian oceanic anoxic event.