| 英文摘要: | Project Abstract
Collaborative Research: A multi-proxy approach to Early Miocene community, landscape, and climate reconstruction, Ethiopian Plateau
Technical 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 importance
5. 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. |