Climatic forcing and tectonic control on environments in evolving lake basins of Africa and North America

非洲和北美演化湖盆环境的气候强迫和构造控制

• 批准号: RGPIN-2020-06653
• 负责人: Scott, Jennifer
• 金额: $ 1.82万
• 依托单位: Mount Royal University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741358
• 关键词: Climatic; forcing; tectonic; control; environments

Orbital cycles, which affect the amount of solar energy on the surface of the Earth, and tectonic activity together controlled paleoenvironments during periods of climate change and evolution. Lake basins are particularly sensitive to changing inputs of precipitation and sediment as influenced by these controls, and preserve the best evidence to interpret changing environments and their impact on paleoecosystems. My research uses detailed studies of sediments and animal behaviour (i.e., trace fossils) to recognize cycles and changing environments in the rock record, used to reconstruct changing landscapes through time. Integrated with other lines of evidence (e.g., minerals, elemental composition, diatom assemblages), we can interpret how conditions in environments change within and between each of the cycles. My research program focuses on three long-term projects: 1) Pliocene lakes of the central Kenya Rift Valley; 2) Pliocene lakes of Afar, Ethiopia; and 3) Cretaceous lakes of Alberta. These projects focus on important periods for evolutionary change, namely the Pliocene-Pleistocene in East Africa, where early humans evolved (~5-1.5 million years ago) during the onset of "icehouse" conditions in the northern hemisphere, and the Cretaceous "greenhouse" of North America, where dinosaur fossils are especially abundant (~80-75 million years ago). Initial results indicate that, in the Baringo Basin of central Kenya where Austrolopithecus and Homo fossils are known after ~3.8 million years ago (Project 1), wide swings in lake level occurred due to orbital cycles and resulted in extremely different environments with periodicity of ~23,000 years (precession) modulated by ~100- and 400-thousand-year eccentricity. These short-term cycles are not the only controls; rifting events and hydrothermal input to the lake basin also influenced the lake system, as did longer term global change in climate, which led to the ice age in the northern hemisphere. Short-term climate cycles are also observed further north in Africa in the Afar region of Ethiopia, where "Lucy" lived during the late Pliocene (~3.5 million years ago; Project 2), but the sedimentary record of these cycles is also complicated by volcanism and faulting events. Once we are able to distinguish the more local geological controls, we can compare between central Kenya and northeast Ethiopia to better interpret the influence of global climate change and changing environments home to early humans. The approach taken for the Plio-Pleistocene will also be applied to a recently recognized lake basin with cyclical deposits in the Cretaceous of Alberta (Project 3) to provide an entirely new look at the potential for climate control on dinosaur evolution. By focusing on tectonically active lake basins during times of climate change and distinct turnover events in animal fossil assemblages, my research impacts our understanding of how Earth and atmospheric processes have repeatedly impacted life on Earth.

影响地球表面太阳能量的轨道周期和构造活动共同控制了气候变化和进化时期的古环境。湖盆对受这些控制影响的降水和沉积物输入的变化特别敏感，并保留了解释环境变化及其对古生态系统影响的最佳证据。我的研究利用对沉积物和动物行为（即痕迹化石）的详细研究来识别岩石记录中的循环和环境变化，用于重建随时间变化的景观。与其他证据（例如矿物质、元素组成、硅藻组合）相结合，我们可以解释每个周期内和周期之间环境条件如何变化。 我的研究计划重点关注三个长期项目：1）肯尼亚裂谷中部的上新世湖泊； 2）埃塞俄比亚阿法尔的上新世湖泊； 3）艾伯塔省的白垩纪湖泊。这些项目重点关注进化变化的重要时期，即东非的上新世-更新世，早期人类在北半球“冰室”条件出现期间进化（约5-150万年前），以及北美的白垩纪“温室”，那里的恐龙化石特别丰富（约80-7500万年前）。初步结果表明，在肯尼亚中部的巴林戈盆地，大约 380 万年前就发现了南方古猿和智人化石（项目 1），由于轨道周期，湖水位发生了大幅波动，并导致了极其不同的环境，其周期性约为 23,000 年（进动），受到约 10 万年和 40 万年偏心率的调节。这些短期周期并不是唯一的控制因素；裂谷事件和热液输入湖盆也影响了湖泊系统，长期全球气候变化也影响了湖泊系统，从而导致了北半球的冰河时代。在非洲更北部的埃塞俄比亚阿法尔地区也观察到了短期气候周期，“露西”生活在上新世晚期（约 350 万年前；项目 2），但这些周期的沉积记录也因火山活动和断层事件而变得复杂。一旦我们能够区分更多的当地地质控制，我们就可以比较肯尼亚中部和埃塞俄比亚东北部，以更好地解释全球气候变化和早期人类居住环境变化的影响。针对上皮里奥-更新世采取的方法也将应用于最近发现的阿尔伯塔省白垩纪有周期性沉积物的湖盆（项目3），以提供一个全新的视角来研究气候控制对恐龙进化的潜力。通过关注气候变化时期构造活跃的湖盆和动物化石组合中独特的周转事件，我的研究影响了我们对地球和大气过程如何反复影响地球生命的理解。