European carbonate margins as recorders of past global change: Cretaceous `greenhouse` versus Carboniferous `coldhouse` examples

化石大陆-海洋边界代表了区域和全球变化的独特档案。化石碳酸盐岩边缘记录了气候、水系格局、沉积物的产生和运输、古海面温度和海水地球化学的变化。我们对两个边缘（西班牙北部和希腊）进行了深入的研究和比较，这两个边缘在全球气候、大气二氧化碳分压、海水成分和碳酸盐岩生产生物群方面代表了地球历史上显著不同的时期。中石炭世边缘（西班牙）代表了一个“冷库”的例子，晚白垩世边缘（希腊）提供了一个地球系统“温室”模式的例子。首先，我们打算集中研究两个边缘的沉积学和层序地层格架。特别关注的是碳酸盐生产潜力的定量确定，以及无机生产与生物诱导和生物控制生产的作用。沉积学研究将导致中石炭世和晚白垩世海平面变化的半定量重建。跨台地-盆地样带的同期剖面可以确定相对海平面波动的幅度。与晚白垩纪相比，这些在中石炭世期间可能会有所不同，当时冰川游动很重要。其次，将d13C、d18O、sr同位素和微量元素比值应用于不同的碳酸盐材料，揭示西班牙化石碳酸盐边缘地球化学记录的海洋表面温度，特别是古温跃层的时空变化。化学地层学（d13C, 87Sr/86Sr）对上白垩统碳酸盐岩边缘对比具有重要意义。本研究的一个特别新颖的方面将是测试和应用Ca同位素（d44Ca）在石炭纪和白垩纪碳酸盐岩的沉积地球化学中，从良好的沉积环境中得到约束。这些结果将与现代热带碳酸盐的岩心材料进行比较，以期获得外源钙循环的新见解。

Fossil continent - ocean boundaries represent unique archives of regional and global change. Changes in climate, drainage patterns, sediment production and transport, palaeo-sea surface temperatures and seawater geochemistry are recorded in fossil carbonate margins. We propose an in-depth study and comparison of two selected margins (Northern Spain and Greece), which represent significantly different episodes of Earth history in terms of global climate, atmospheric pCO2, seawater composition and carbonate producing biota. The mid-Carboniferous margin (Spain) represents a "coldhouse" example and the Late Cretaceous margin (Greece) provides an example of the "greenhouse" mode of Earth´s system. Firstly, we intend to concentrate on the sedimentologic and sequence stratigraphic framework of both margins. A special focus will be on the quantitative determination of the carbonate production potential, and the role of inorganic versus biologically induced and biologically controlled production. Sedimentological studies will lead to a semi-quantitative reconstruction of middle Carboniferous and Late Cretaceous sea-level changes. Coeval sections across platform-to-basin transects allow for a determination of amplitudes of relative sea-level fluctuations. Compared to the Late Cretaceous these are expected to be different during the middle Carboniferous when glacial eustasy was important. Secondly, we will apply d13C, d18O, Sr-isotopes and trace element ratios to different carbonate materials in order to reveal spatial and temporal variability of sea-surface temperatures and specifically of the palaeo-thermocline recorded in the geochemistry of fossil carbonate margins in Spain. Chemostratigraphy (d13C, 87Sr/86Sr) will be important for the correlation of Upper Cretaceous carbonate margins. A particular novel aspect of this study will be the testing and application of Ca isotopes (d44Ca) to the sedimentary geochemistry of Carboniferous and Cretaceous carbonates from well constrained depositional settings. These results will be compared to core material from modern tropical carbonates with the expectation to gain new insight in the exogenic calcium cycle.