Ordovician-Silurian graptolite phylogeny, biodiversity history, chronostratigraphy, paleoenvironmental cycles, and oceanic anoxia

奥陶纪-志留纪笔石系统发育、生物多样性历史、年代地层学、古环境循环和海洋缺氧

• 批准号: 133748-2013
• 负责人: Melchin, Michael
• 金额: $ 1.97万
• 依托单位: St. Francis Xavier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633842
• 关键词: Ordovician; Silurian; graptolite; phylogeny; biodiversity

The Ordovician and Silurian periods (ca. 500-420 million years ago) were times of dramatically changing climate, sea level, and biodiversity. One of the biggest mass extinction events in Earth History occurred near the end of the Ordovician Period. The most important group of animals preserved in the marine plankton during these time periods was the graptolites, a group of mostly extinct hemichordates. They were abundant, geographically widespread and evolved rapidly, which makes them excellent fossils for identifying short intervals of geologic time and correlation of those intervals around the globe. A thorough understanding of these organisms and their distribution in sedimentary strata maximizes our potential to use them to solve a wide range of geological problems in areas such as tectonics, sedimentary basin history, and climate change. My research program has several major objectives: 1) reconstruction of the evolutionary history of graptolites; 2) understanding the history of change of graptolite biodiversity as a result of changing rates of species origination and extinction, particularly through the cycles of climatic and oceanic changes that characterize the Ordovician and Silurian periods; and 3) studying the physical and chemical record preserved in rock strata to better understand the environmental cycles and their causes. For the last objective, I am particularly interested in the history of anoxia in the oceans - times when large areas of the ocean became depleted in oxygen. I am working on detection of oceanic anoxia using geochemical and isotopic signals, and understanding anoxia in terms of its relationship to changes in climate, ocean circulation and biological productivity. I will also use the graptolites and their occurrences in sedimentary strata to improve the resolution with which we can define and subdivide geological time. By improving our resolution of geological time, we can gain clearer insights into the timing and rates of evolutionary and paleoenvironmental processes. This research into the long-term links between climate change, ocean circulation and biodiversity will provide insights that will help us better understand the modern world of changing climate and biodiversity.

奥陶纪和志留纪（约 500-4.2 亿年前）是气候、海平面和生物多样性发生巨大变化的时期。地球历史上最大的大规模灭绝事件之一发生在奥陶纪末期。在这些时期，海洋浮游生物中保存的最重要的动物类群是笔石，这是一组大部分已灭绝的半索动物类。它们数量丰富、地理分布广泛且进化迅速，这使它们成为识别地质时间的短间隔以及全球这些间隔的相关性的极好化石。对这些生物及其在沉积地层中的分布的透彻了解可以最大限度地发挥我们利用它们解决构造、沉积盆地历史和气候变化等领域的广泛地质问题的潜力。我的研究计划有几个主要目标：1）重建笔石的进化历史； 2）了解笔石生物多样性由于物种起源和灭绝速率变化而变化的历史，特别是通过奥陶纪和志留纪时期的气候和海洋变化周期； 3）研究岩层中保存的物理和化学记录，以更好地了解环境循环及其原因。对于最后一个目标，我对海洋缺氧的历史特别感兴趣——当时海洋大面积缺氧。我正在研究利用地球化学和同位素信号检测海洋缺氧，并了解缺氧与气候、海洋环流和生物生产力变化的关系。我还将利用笔石及其在沉积地层中的出现来提高我们定义和细分地质时间的分辨率。通过提高地质时间的分辨率，我们可以更清楚地了解进化和古环境过程的时间和速率。这项对气候变化、海洋环流和生物多样性之间长期联系的研究将提供见解，帮助我们更好地了解气候和生物多样性不断变化的现代世界。