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.

奥陶纪和志留纪时期（大约500-42亿年前）是气候，海平面和生物多样性的急剧变化的时代。地球历史上最大的巨大灭绝事件之一发生在奥陶纪时期结束时。在这段时间内，保存在海洋浮游生物中的最重要的动物是Graptolites，这是一组灭绝的半色。它们是丰富的，地理上广泛的，并且迅速发展，这使它们成为识别全球这些间隔的短时间间隔和相关性的出色化石。对这些生物的透彻理解及其在沉积地层中的分布最大化我们利用它们来解决诸如构造，沉积盆地历史和气候变化等地区的广泛地质问题。我的研究计划有几个主要目标：1）重建graptolites的进化史； 2）了解物种起源和灭绝率的变化，尤其是通过气候变化和海洋变化的循环，理解graptolite生物多样性的变化历史，这些变化是奥陶纪和志留纪时期的特征； 3）研究保留在岩层中的物理和化学记录，以更好地了解环境周期及其原因。对于最后一个目标，我对海洋中的缺氧史特别感兴趣 - 当海洋的大片地区耗尽氧气时。我正在使用地球化学和同位素信号来检测海洋缺氧，并了解其与气候变化，海洋循环和生物生产力的关系的关系。我还将在沉积地层中使用graptolites及其发生，以改善我们可以定义和细分地质时间的分辨率。通过改善我们的地质时间解决方案，我们可以对进化和古环境过程的时机和速度有更清晰的见解。这项研究气候变化，海洋流通和生物多样性之间的长期联系将提供见解，以帮助我们更好地了解不断变化的气候和生物多样性的现代世界。