Collaborative Research: A multi-proxy approach to Early Miocene community, landscape, and climate reconstruction, Ethiopian Plateau

项目摘要合作研究：埃塞俄比亚高原早期中新世群落、景观和气候重建的多代理方法技术描述：新生代岩石记录包含丰富且至关重要的不同气候和生物群落的历史，这些有助于了解当前和未来的气候和生物变化。虽然规模不同，但深厚的地质历史提供了可以比较气候模型或创建气候模型的测试案例。 然而，古气候代理的空间覆盖范围在中纬度地区最好，而在热带和亚热带地区，特别是在陆地领域，则相当有限。该项目将调查一个新的非凡的早中新世（22 Ma）遗址，那里的碳质页岩和凝灰质沉积物保存着拉格斯塔滕品质的化石，包括丰富的压缩树叶、具有精美角质层特征的水果和种子、具有骨骼和软体部分的完整青蛙、鱼类和大型哺乳动物骨骼。这些可以重建古气候、pCO2、古生态学以及非洲植物区系甚至动物区系的重要生物地理数据。 该项目的目标是： 1．使用多个独立代理比较早中新世和晚渐新世的古气候、古生态学和生物地理学。2．提供成土针铁矿和气孔指数的 pCO2 估计值。3．为非洲的一个鲜为人知但重要的时间间隔内的动物群进化提供早期中新世的古生态和古气候背景。 4. 解决植物生物地理学问题，例如棕榈树的丰富度和重要性下降5。测试方法包括：(a) 比较水生和陆地脂质中的 D 同位素，以测试蒸散引起的 D 富集；(b) 比较针铁矿和气孔指数 pCO2 数据；(c) 使用基于叶子面貌、植物分类群重叠范围、定性和定量古土壤分析以及多种同位素地球化学代理的方法评估古温度和降水重建的一致性。非技术描述和更广泛的意义：这笔赠款资助了一个多学科科学家团队，他们将从亚的斯亚贝巴东北部的埃塞俄比亚高原采集岩石和化石样本，以综合协作的方式重建过去的气候、植被、大气二氧化碳浓度 (pCO2) 和 2200 万年前的自然景观。团队成员曾在距今 2700 万年前的高原岩石上进行过合作，他们在植物化石鉴定、昆虫对化石叶子的破坏、过去气候和生态的重建、古代土壤和有机植物化合物的地球化学以及地质学方面拥有专业知识。该地区保存着具有细胞细节的非凡植物化石、保存有软组织的青蛙等小型脊椎动物以及大型哺乳动物骨骼。 我们工作的科学意义在于，它将解决目前关于 2700 万至 2200 万年前全球温度和 pCO2 的相互矛盾的数据。 海洋记录显示，这段时间全球气温显着上升，但 pCO2 的一些记录显示下降，另一些记录则上升。 通过使用多个独立来源从一个地区获取温度和二氧化碳分压数据来解决这一冲突，将告诉我们对二氧化碳相对于全球温度的理解是否正确。 此外，非洲和欧亚大陆之间的现代陆地联系大约在2400万年前建立，因此我们将能够将较年轻的动植物化石与欧亚大陆接触之前的动植物化石进行比较。 此时非洲的动植物群正处于过渡时期，其文献记录对于了解现代生物群落的起源非常重要。教育外展包括为数千名 K-12 学生提供远程学习。 该团队拥有博客历史，目前由 SMU 公共事务办公室在主网站上托管，最近还通过《纽约时报工作科学家》页面托管。学生将成为这个项目不可或缺的一部分？该团队定期带学生前往实地考察，并将继续这样做。 我们还计划接待一名埃塞俄比亚研究生到美国接受培训。

Project Abstract Collaborative Research: A multi-proxy approach to Early Miocene community, landscape, and climate reconstruction, Ethiopian PlateauTechnical Description: The Cenozoic rock record contains a rich and critically important history of varied climates and biotic communities, and these serve as aids to understanding current and future climatic and biotic change. While the scales are different, the deep geologic past provides test cases against which climate models can be compared or from which they can be created. However, spatial coverage by paleoclimate proxies is best for middle latitudes, and quite limited for the tropics and subtropics, especially in the terrestrial realm. This project will investigate a new extraordinary Early Miocene (22 Ma) site where carbonaceous shales and tuffaceous sediments preserve lagerstätten-quality fossils including abundant compressed leaves, fruits and seeds with exquisite cuticular features, complete frogs with both skeletal and soft body parts, fish and large mammal bones. These enable reconstruction of paleoclimate, pCO2, paleoecology, and significant biogeographic data for African flora, and perhaps fauna. The objectives of this project are to:1. compare Early Miocene and Late Oligocene paleoclimate, paleoecology, and biogeography using multiple independent proxies.2. provide pCO2 estimates from pedogenic goethite and stomatal indices.3. provide Early Miocene paleoecological and paleoclimatological context for faunal evolution during an otherwise poorly known, but significant time interval for Africa. 4. address plant biogeographic questions, e.g. a decline in palm richness and importance5. test methods by (a) comparing δD isotopes from aquatic and terrestrial lipids to test for enrichment of D due to evapotranspiration, (b) comparing goethite and stomatal index pCO2 data (c) evaluating the consistency of paleotemperature and precipitation reconstructions using methods based upon leaf physiognomy, overlapping ranges of plant taxa, qualitative and quantitative paleosol analyses, and multiple isotope geochemical proxies. Non-technical Description and Broader Significance: This grant funds a multidisciplinary team of scientists who will sample rocks and fossils from the Ethiopian Plateau northeast of Addis Ababa to reconstruct past climate, vegetation, atmospheric CO2 concentration (pCO2), and the physical landscape 22 million years ago in an integrated and collaborative way. Team members, who have collaborated before on rocks from the Plateau that are 27 million years old, have expertise in the study of plant fossil identification, insect damage to fossil leaves, the reconstruction of past climate and ecology, the geochemistry of ancient soils and organic plant compounds, and geology. The locality preserves extraordinary plant fossils having cellular detail, smaller vertebrates including frogs with soft tissue preservation, and large mammal bones. The scientific significance of our work is that it will resolve currently conflicting data regarding global temperature and pCO2 between 27 million and 22 million years ago. Marine records show a significant rise in global temperature between these times, but some records of pCO2 show a decline and others a rise. Resolution of this conflict by acquisition of temperature and pCO2 data from one region using multiple independent sources will tell us if our understanding of CO2, in relation to global temperature is correct. Furthermore, the modern land connection between Africa and Eurasia was established about 24 million years ago, so we will be able to compare the younger plant and animal fossils with those from a time prior to contact with Eurasia. Africa?s flora and fauna was in a period of transition at this time, and its documentation is important for understanding the origins of modern biomes. Educational outreach includes distance learning for thousands of K-12 students. This team has a history of blogs, currently hosted by the SMU Public Affairs office on the main website, and recently through the NY Times Scientist at Work pages. Students will be an integral part of this project ? this team has regularly taken students into the field and will continue to do so. We also plan to host an Ethiopian graduate student for training in the U.S.