Inoceramid sclerochronology - Advancing Late Cretaceous climate reconstructions

白垩纪是温室世界的一个典型例子，属于地球历史上研究得最好的时间间隔之一。然而，仍然不确定不同纬度和水深的实际温度，而且当时对热带外海洋的季节性和年际环境变化几乎一无所知。这些信息对于约束纬向温度梯度、核实极地冰的存在与否、检验关于大气和海洋环流模式的假设以及进一步完善数值气候模型至关重要。它也可用于更详细地研究沉积和轨道强迫之间的联系，因为后者会改变季节性温度模式。此外，高分辨率温度（和其他环境）数据有助于更好地了解物种分布模式、生物的古生物学和生活史特征以及分类群兴起和消亡的潜在原因。一个有前途的档案破译季节到年际气候动力学在extratrophic白垩纪海洋-其全部潜力还没有被探索-是包含在壳inoceramid双壳类。这个特殊的物种群出现在二叠纪，但由于未知的原因，在白垩纪/古近纪边界之前几百万年就灭绝了。尽管经过数十年的研究，对inoceramids的生物学，生态学和生活史特征知之甚少，但它们在中生代晚期的温室气候中蓬勃发展。在晚白垩世，它们明显地主导了热带外的巨型动物群。巨大的贝壳尺寸可达3米（！），inoceramids属于有史以来最大的双壳类动物。Inoceramids栖息在几乎任何水深，甚至大量出现在恶劣的，dysopolymerization环境。通过应用最先进的硬年代学技术结合广泛的成岩作用筛选试验，拟议的研究将铺平道路，走向常规使用的inoceramid双壳类在高分辨率的古气候学。为了证明这个档案的潜力，我们将举例研究季节性温度如何变化（1）在白垩纪温室，即之前，期间和之后OAE 2（森诺曼/图伦阶段边界;明斯特兰盆地）和（2）在坎帕尼亚阶段（北海道）。(3)此外，还将分析根据不同岩石类型（明斯特兰盆地）的贝壳重建的季节性环境变量之间是否存在差异。如果沉积作用是轨道强迫的，那么石灰岩和泥灰岩沉积时期的季节温度、初级生产力等应该是不同的。（四） 此外，将确定选定的inoceramid类群的生活史性状，包括个体发育年龄以及季节性壳生长的时间和速率。

The Cretaceous serves a classic example of a greenhouse world and belongs to one of the best studied time intervals of Earth history. However, it still remains uncertain which actual temperatures prevailed at different latitudes and water depths, and almost nothing is known about the seasonal and inter-annual environmental variability in extratropical oceans at that time. Such information is essential to constrain meridional temperature gradients, verify the presence or absence of polar ice, test hypotheses on atmospheric and oceanic circulation patterns and further refine numerical climate models. It may also be used to study the link between sedimentation and orbital forcing in more detail, because the latter modifies seasonal temperature patterns. Furthermore, high-resolution temperature (and other environmental) data can help to better understand species distribution patterns, the paleobiology and life history traits of organisms as well as potential causes for the rise and demise of taxa. A promising archive for deciphering seasonal to inter-annual climate dynamics in extratropical Cretaceous oceans - whose full potential has by far not been explored - is contained in shells of inoceramid bivalves. This peculiar species-group appeared in the Permian and, for yet unknown reasons, became extinct several million years prior to the Cretaceous/Paleogene boundary. Despite decades of research, not particularly much is known about the biology, ecology and life-history traits of the inoceramids, but they thrived in the greenhouse climate of the late Mesozoic. During the Late Cretaceous, they clearly dominated the extratropical megafauna. With enormous shell sizes of up to 3m (!), inoceramids belong to the largest bivalves that ever lived. Inoceramids inhabited nearly any water depth and even occurred abundantly in hostile, dysoxic environments. By applying state-of-the-art sclerochronological techniques combined with a broad spectrum of diagenesis screening tests, the proposed study will pave the way toward a routine use of inoceramid bivalves in high-resolution paleoclimatology. To demonstrate the potential of this archive, we will exemplarily study how seasonal temperatures changed (1) during the Cretaceous hothouse, i.e. before, during and after OAE2 (Cenomanian/Turonian stage boundary; Münsterland Basin) and (2) during the Campanian stage (Hokkaido). (3) In addition, it will be analyzed if a difference exists between seasonal environmental variables reconstructed from shells of different rock types (Münsterland Basin). If sedimentation was orbitally forced, seasonal temperatures, primary productivity etc. should have differed between times of limestone and marl deposition. (4) Furthermore, the life history traits of selected inoceramid taxa will be determined including ontogenetic ages as well as the timing and rate of seasonal shell growth.