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各种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。虽然尺度不同，但深部地质过去提供了测试案例，可以与气候模型进行比较，或者根据这些案例创建气候模型。然而，古气候指标的空间覆盖范围在中纬度地区是最好的，在热带和亚热带地区是相当有限的，特别是在陆地领域。该项目将调查一个新的非同寻常的中新世早期(22 Ma)遗址，在那里碳质页岩和凝灰岩沉积物保存了Lagerstätten优质化石，包括丰富的扁平叶子、具有精致角质特征的果实和种子、具有骨骼和柔软身体部分的完整青蛙、鱼类和大型哺乳动物骨骼。这使得能够重建古气候、二氧化碳、古生态和重要的非洲植物，或许还有动物的生物地理数据。该项目的目标是：1.利用多个独立的代理对早中新世和晚渐新世的古气候、古生态和生物地理进行比较。提供成壤针铁矿和气孔指标的二氧化碳估计值。为非洲在鲜为人知但意义重大的时间间隔内的动物群演化提供了早期中新世的古生态和古气候背景。4.解决植物生物地理问题，例如棕榈树丰富度和重要性的下降5.测试方法：(A)比较水生和陆地脂肪中的D同位素，以测试蒸发蒸腾对D的富集度；(B)比较针铁矿和气孔指数二氧化碳数据；(C)使用基于树叶地貌、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指标的方法，评估古温度和降水重建的一致性。非技术性描述和更广泛的意义：这笔赠款资助了一个多学科的科学家团队，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，以综合和合作的方式重建2200万年前的过去气候、植被、大气二氧化碳浓度(PCO2)和物理景观。团队成员之前曾在来自高原的2700万年前的岩石上进行过合作，他们在植物化石识别、昆虫对化石叶子的破坏、重建过去的气候和生态、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。该地区保存了具有细胞细节的非凡植物化石，包括软组织保存的青蛙在内的较小脊椎动物，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2200万年前全球气温和二氧化碳含量的相互矛盾的数据。海洋记录显示，在这两个时间段之间，全球气温显著上升，但一些二氧化碳记录显示下降，另一些记录上升。通过使用多个独立来源从一个地区获取温度和二氧化碳数据来解决这一冲突，将告诉我们我们对二氧化碳与全球气温的理解是否正确。此外，非洲和欧亚大陆之间的现代陆地连接是在大约2400万年前建立的，因此我们将能够将较年轻的动植物化石与与欧亚大陆接触之前的那些化石进行比较。非洲？S的动植物此时正处于过渡时期，其记载对于了解现代生物群的起源具有重要意义。教育外展包括为数千名K-12学生提供远程学习。这个团队有博客的历史，目前由SMU公共事务办公室在主网站上托管，最近通过纽约时报科学家在工作页面上托管。学生将是这个项目不可或缺的一部分吗？这个团队经常把学生带到现场，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.