Magnetostratigraphy of Pleistocene Sediments from the Republic of Georgia - Dating and Correlation of Climate Signals

格鲁吉亚共和国更新世沉积物的磁性地层学 - 气候信号的年代测定和相关性

• 批准号: 245125135
• 负责人: Professor Dr. Valerian Bachtadse
• 金额: --
• 依托单位: Sektion Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/245125135?language=en
• 关键词: Magnetostratigraphy; Pleistocene; Sediments; Republic; Georgia

The discovery of hominin remains of as many as six individuals, approx. 1.8 Ma in age, in Dmanisi, Southern Georgia, marks the first appearance of human occupation in Eurasia, significantly earlier than previously thought and thus changed our understanding of the causes of the first wave of emigration out of Africa substantially. Recent studies have shown, that the only African elements in the Dmanisi site are the remains of Homo Georgicus itself and associated tools. Unambiguous European affinities of the Dmanisi fauna do not support the idea, that the early hominins followed the migration patterns of large herbivores to ensure their food supply. The details of the Dmanisi hominins furthermore suggest, that local or global changes in climate are the key driving factor for early humans to venture towards Europe, because other hypothesis are disproved. In the early Pleistocene, rapid changes of warm/cold periods are documented based on global oxygen isotope records. It has been proposed, that during one of the warm periods the onset of desertification in eastern Africa forced early hominins to migrate into Europe. It is debated, however, whether the human remains in Georgia demonstrate favorable climatic conditions for early hominins and prove a long term occupation of this area, or the Caucasus represents a stepping stone along a migration path into Eurasia. For investigation of local climatic conditions, high resolution palynology is an ideal technique to map the paleoenvironmental conditions and local responses to global climate. For such studies, however, very precise age control isinevitable.High resolution magnetostratigraphy has been shown to be a very precise correlation and dating tool especially concerning young sediments. Thus, magnetostratigraphy provides the basis for successful studies of short term variations of the paleoenvironment.In Western Georgia there are a number of sedimentary sections with proposed deposition ages from ~3 million years up to the present. This time span includes the hominid bearing deposits at Dmanisi as well as lake sediments from Armenia studied earlier (Ba1210/14-1). What makes the Georgian shallow marine sections special, however, is the extremely large amounts of pollen which can give a high resolution picture of the paleoenvironmental conditions during times of human migration through the Caucasus. Correlating the magnetostratigraphic data from Georgia with those from Armenia will allow us to compare the climatic situation in Western Georgia and Armenia during the Pleistocene.It is therefore planned to study two large sections in Guria which cover a sufficiently long time span to include the 1.8 Ma time mark (age of the Dmanisi hominins) and the southern Armenian sections. The results of this study will contribute to a precise reconstruction of the paleoclimate and paleoenvironment of the Caucasus during a crucial phase of hominin occupation in the area.

发现的古人类遗骸大约有六具。在乔治亚州南部的德马尼西（Dmanisi），距今1.8万年的时间标志着人类首次在欧亚大陆出现，比之前认为的要早得多，从而大大改变了我们对非洲第一波移民浪潮原因的理解。最近的研究表明，德马尼西遗址中唯一的非洲元素是乔治人本身和相关工具的遗骸。德马尼西动物群与欧洲动物群的明确相似性并不支持早期人类遵循大型食草动物迁徙模式以确保食物供应的观点。德马尼西古人类的细节进一步表明，当地或全球气候的变化是早期人类冒险前往欧洲的关键驱动因素，因为其他假设都被推翻了。在更新世早期，全球氧同位素记录记录了暖/冷期的快速变化。有人提出，在一个温暖时期，非洲东部沙漠化的开始迫使早期人类迁移到欧洲。然而，人们争论的是，格鲁吉亚的人类遗骸是否证明了早期人类的有利气候条件，并证明了该地区的长期占领，或者高加索地区代表了通往欧亚大陆的迁徙之路的垫脚石。高分辨率孢粉学是研究局部气候条件的一种理想技术，可以反映古环境条件和局部对全球气候的响应。然而，对于这样的研究，非常精确的年龄控制是不可避免的。高分辨率磁地层学已被证明是一种非常精确的对比和测年工具，特别是对年轻沉积物而言。因此，磁地层学为成功研究古环境的短期变化提供了基础。在格鲁吉亚西部，有许多沉积剖面，其沉积年龄从300万年到现在不等。这个时间跨度包括德马尼西的古人类沉积物以及早期研究的亚美尼亚湖泊沉积物（Ba1210/14-1）。然而，格鲁吉亚浅海剖面的特别之处在于大量的花粉，这些花粉可以提供人类穿越高加索地区迁徙时期的古环境条件的高分辨率图像。将格鲁吉亚的磁地层资料与亚美尼亚的磁地层资料进行对比，可以比较更新世时期格鲁吉亚西部和亚美尼亚的气候情况。因此，计划研究古里亚的两个大部分，它们涵盖了足够长的时间跨度，包括1.8 Ma时间标记（德马尼西人族的时代）和亚美尼亚南部部分。本研究的结果将有助于精确重建高加索地区在人类居住的关键时期的古气候和古环境。