Size reductions during hyperthermal events: early warnings of environmental deterioration or signs of extinction? (EarlyWarn)

在灭绝时期，连续化石组合的尺寸缩小是在各种时间和空间尺度上可见的主要特征。然而，潜在的环境驱动因素和机制仍存在争议。在各种情况下，大小反应早于主要的灭绝脉冲，这表明它们可能预示着早期的环境破坏。这里提出的项目旨在明确地模拟层序地层框架中的大小变化，以区分局部古环境对这些模式的影响与全球的影响。这种方法将侧重于伊朗二叠纪-三叠纪剖面和欧洲不同的普连斯巴克奇-托尔西亚剖面的软体动物和腕足类组合的相内和相间比较，因此涵盖了灭绝事件之前和灭绝事件之间的广泛的古环境和保存背景。这些方法对于在过滤潜在的采集和地层偏差时，在驱动模式中定量地理清气候相关应激源和养分可获得性的相对贡献是必要的。该项目的最后部分将把我们新收集的高分辨率数据与新添加的大型数据集进行比较，考虑到合适的相、层序地层学和地球化学背景，以了解它们在关于小型化这些方面(“利力普特效应”)的第一次全面荟萃分析中的相对贡献。这些数据集还将用于理清物种内大小减少、大小选择性灭绝/迁徙和起源/迁徙在背景条件下以及从轻微生物危机到与高温事件相关的大规模灭绝等事件期间推动大小波动的相对贡献。

Size reductions in successive fossil assemblages during times of extinction are major features visible across a variety of temporal and spatial scales. The underlying environmental drivers and mechanisms are however still debated. In various cases, size responses predate the main extinction pulse suggesting that they might signal early environmental disruptions. The project proposed here aims to explicitly model size changes in a sequence stratigraphic framework to disentangle the local paleoenvironmental influences on these patterns from global ones. This approach will focus on within-facies and between-facies comparisons of mollusk and brachiopod assemblages of Permian-Triassic sections in Iran and various European Pliensbachian-Toarcian sections, hence covering a wide range of paleoenvironmental and preservational contexts before and across extinction events. These approaches are necessary to quantitatively disentangle the relative contribution of climate-related stressors and nutrient availability in driving patterns when filtering out potential collection and stratigraphy biases. The final part of the project will compare our newly collected high-resolution data with newly appended large size datasets considering appropriate facies, sequence stratigraphic and geochemical context to understand their relative contribution in the first comprehensive meta-analysis on these aspects of miniaturization (“Lilliput effect”). These datasets will also be used to disentangle the relative contribution of within-species size reductions, size-selective extinction/immigration and origination/immigration in driving size fluctuations during background conditions as well as during events ranging from minor biological crises to mass extinctions associated with hyperthermal events.