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

人类遗骸的发现多达六个个体，大约。1.8 Ma，在格鲁吉亚南部的德马尼西，标志着欧亚大陆首次出现人类占领，比之前认为的要早得多，从而极大地改变了我们对非洲第一波移民潮原因的理解。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的遗骸和相关工具。欧洲明确的德马尼西动物群的亲缘关系并不支持这样的观点，即早期的原始人遵循大型食草动物的迁徙模式，以确保它们的食物供应。德玛尼西原始人的细节进一步表明，局部或全球气候变化是早期人类冒险前往欧洲的关键驱动因素，因为其他假设是错误的。在早更新世，根据全球氧同位素记录，记录了暖冷期的快速变化。有人提出，在一个温暖的时期，东非荒漠化的开始迫使早期原始人迁徙到欧洲。然而，佐治亚州的人类遗骸是否显示出有利于早期古人类生存的气候条件，并证明该地区长期占据着这一地区，还是高加索地区代表着进入欧亚大陆的迁徙路径上的垫脚石，这一点存在争议。对于当地气候条件的调查，高分辨率孢粉学是绘制古环境条件和当地对全球气候响应的理想技术。然而，对于这样的研究，非常精确的年龄控制是不可避免的。高分辨率磁性地层学已经被证明是一种非常精确的对比和测年工具，特别是对于年轻的沉积物。因此，磁性地层学为成功研究古环境的短期变化提供了基础。在佐治亚州西部有许多沉积剖面，其沉积年龄从大约300万年到现在。这一时间跨度包括德马尼西的原始人类沉积以及早先研究的亚美尼亚的湖泊沉积物(Ba1210/14-1)。然而，格鲁吉亚浅海剖面的特殊之处在于，极大量的花粉可以给出人类通过高加索迁徙期间的古环境条件的高分辨率图像。将来自格鲁吉亚的磁性地层数据与来自亚美尼亚的数据进行对比，将使我们能够比较更新世期间格鲁吉亚西部和亚美尼亚的气候状况。因此，我们计划研究古里亚的两大段，这两段覆盖的时间跨度足够长，包括1.8 Ma的时间标志(德马尼西人的年龄)和亚美尼亚南部的部分。这项研究的结果将有助于准确重建高加索地区原始人占领的关键阶段的古气候和古环境。

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.