Ocean acidification and biocalcification crisis at the Triassic-Jurassic boundary

三叠纪-侏罗纪边界的海洋酸化和生物钙化危机

• 批准号: 36350684
• 负责人: Professor Dr. Bas van de Schootbrugge
• 金额: --
• 依托单位: Utrecht University
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2007-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/36350684?language=en
• 关键词: Ocean; acidification; biocalcification; crisis; Triassic

Causes for the Triassic-Jurassic boundary mass-extinction event (Tr-J; 199.6 Ma) remain poorly understood. One popular extinction scenario envisions a role for the massive release of volatiles (CO2, SO2) from the outflow of voluminous amounts of flood basalt. Evidence for a role of flood basalt volcanism in Tr-J extinctions include: (1) a rapid four-fold rise in pCO2, documented by plant leaf stomata, (2) simultaneous, large negative carbon isotope excursions in carbonate and organic carbon pools and (3) gradual, rather than catastrophic, extinctions and turnover in many groups of marine and terrestrial biota. In analogy with the predicted impact of anthropogenic CO2 emissions on ocean chemistry, it can be hypothesized that a major consequence of a rapid and significant increase in pCO2 is the acidification of the surface ocean (pH decrease) and hence a decrease in carbonate saturation ([CO3 2 ] decrease), leading to a biocalcification crisis. Indeed, shallow marine carbonate-producing organisms, such as hermatypic scleractinian corals, bivalves and coccolithophorids, show some of the highest extinction rates during the latest Rhaetian, and reef building was disrupted worldwide for several million years after the Tr-J boundary. Furthermore, the Early Jurassic appears to mark a brief interlude of extensive calcite deposition in shallow marine settings during a time of predominant Aragonite Seas. In response to a halt in biogenic carbonate production, increased alkalinity may have been mediated by abiogenic carbonate precipitation in the form of widespread deposition of calcite ooids, low-magnesium calcite marine cements and/or microbially in the form of extensive micritic precipitates and microbialites. The aim of this research project is to find sedimentological and geochemical evidence for this hypothesized biocalcification crisis by studying in detail Tr-J boundary sections along the northern and southern margins of the Tethys in the Southern Alps, Lessini Mountains and Carpathian Mountains. The gathered results will serve as a pilot study for the further development of future research projects.

三叠纪-侏罗纪边界大规模灭绝事件（Tr-J; 199.6 Ma）的原因仍然知之甚少。一种流行的灭绝情景设想了大量的挥发物（CO2，SO2）从大量的洪水玄武岩流出的作用。洪水玄武岩火山作用在Tr-J灭绝中的作用的证据包括：（1）pCO 2迅速上升四倍，由植物叶片气孔记录，（2）碳酸盐和有机碳库中同时出现大的负碳同位素偏移，（3）许多海洋和陆地生物群中的灭绝和周转是渐进的，而不是灾难性的。与预测的人为CO2排放对海洋化学的影响相类比，可以假设pCO 2快速显著增加的主要后果是海洋表层酸化（pH值下降），从而导致碳酸盐饱和度下降（[CO 3 2 ]下降），导致生物钙化危机。事实上，浅海产碳酸盐生物，如造礁石石珊瑚、双壳类和颗石珊瑚，在最后一个雷期的灭绝率最高，在Tr-J边界之后的几百万年里，世界范围内的珊瑚礁建造被中断。此外，早侏罗世似乎标志着一个短暂的插曲，广泛的方解石沉积在浅海环境中的时间占主导地位的文石海。在响应生物碳酸盐生产的停止，碱度增加可能已介导的非生物碳酸盐沉淀的形式广泛沉积的方解石类卵，低镁方解石海洋胶结物和/或微生物的形式广泛的泥晶沉淀物和微生物。该研究项目的目的是通过详细研究南阿尔卑斯山脉、莱西尼山脉和喀尔巴阡山脉特提斯北方边缘沿着Tr-J边界剖面，为这一假设的生物钙化危机找到沉积学和地球化学证据。收集的结果将作为进一步发展未来研究项目的试点研究。