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31.
The loess mounds are a newly discovered type of landforms on the Laizhou Bay plain south of the Bohai Sea. Research shows that they were formed in the late period of the late Pleistocene when the Bohai Sea was exposed in the period of late Wümu glacial age and changed into plain. As the exposed area is not protected by vegetation, the sediments at the sea bottom are blown and transported southward by strong north winds, and deposit on the coastal plains. As thick loess is accumulated, the loess mound landforms are formed in the direction of down wind. 相似文献
32.
根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48~139.2m的高位湖相沉积;在拔湖26m以下,发育有8~30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5~19.8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9~71.8kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7~28.2kaB.P.的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3kaB.P.;第2至第1级阶地,14C测定结果为2350~10390aB.P.。 相似文献
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34.
The application of both thermoluminescence and infrared stimulated luminescence dating to the extensively studied “classical” Hungarian loess/paleosol sequences from Basaharc, Mende, and Paks provides a reliable chronological framework and climatostratigraphic reconstruction for the last interglacial/glacial cycle. Based on this combined luminescence dating study a new chronology is proposed for the “Young Loess” in Hungary. Luminescence dating suggests that the loess below the MF2 horizon formed during the penultimate glaciation. The MF1 horizon probably formed during an interstade within oxygen isotope stage 3. For the youngest loess, overlying MF1, a very high accumulation rate was determined. Large time gaps occur above MF2 and MF1, indicating that most of the record of the last glaciation is missing in the standard sections at Basaharc, Mende, and Paks. Either large discontinuities or a very low accumulation rate occurred in all three type sections during the soil-forming periods. High-resolution studies of climatic proxies using this combined luminescence dating approach provide a reliable chronological framework for loess and loess derivatives of the last glacial cycle in Hungary, although a precise and complete chronostratigraphic reconstruction cannot be achieved from the incomplete records found at these sites. 相似文献
35.
陕西关中晚更新世黄土—古土壤序列特征及其记录的古环境变迁 总被引:7,自引:1,他引:7
陕西关中盆地的泾阳南塬和西安东郊席王晚更新世黄土剖面底部的S1古生境是由4层古土壤及与其相间的两层古土壤构成。这是目前发现的黄土高原晚更新世黄土,古土壤序列保存较好的剖面。两剖面的地层结构,磁化率曲线和地球化学组分反映出了12个温湿,冷干气候变化阶段可以归纳为6个气候变化旋回。 相似文献
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37.
根据野外水准测量与室内实验分析,本文探讨了西藏纳木错和藏北高原古大湖晚更新世以来的湖泊演化和气候变迁。在纳木错沿岸拔湖48m以下,发育了6级湖岸阶地,拔湖48-139.2m发育有高位湖相沉积。研究表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116-37ka B.P.间的古大湖期;②37-30ka B.P.间的外流湖期;③30kaB.P.以来的纳木错期。在古大湖阶段,包括纳木错、色林错和扎日南木错、当惹雍错等藏北高原东南部的一大批现代大、中、小型湖泊,都是互相连通的一个古大湖,其范围可能超过了现代的藏北内、外流(怒江)水系的分水岭。它或许还与藏北高原南部和西部的其他古湖相连,成为统一的藏北高原“古大湖”。通过对纳木错湖相沉积形成时代与深海氧同位素对比,易溶盐、pH值、地球化学、介形类和孢粉分析等的综合研究发现,湖相沉积记录了自晚更新世以来的湖泊演化和气候变迁信息。资料显示古大湖期湖面最高,气候温和清爽;外流湖期湖面急剧下降,气温和湿度较现今略高;纳木错期以来气候经历了全新世最宜期的暖湿后日益干旱化,气温波动,湖面持续下降。表明自晚更新世以来该区气候在逐渐变干的总趋势的基础上,经历了多次明显的冷暖与干湿波动。 相似文献
38.
长江上游三峡河段主要的古洪水记录有:1)三峡深槽的蚀积变化;2)长江阶地粗粒沉积;3)长江的泛滥沉积;4)长江的古洪水平流沉积。不同时间跨度不同类型古洪水记录的精度有较大的差别。古洪水记录显示,晚更新世晚期的40~30kaB.P.,长江上游大洪水比30kaB.P.以来的长江上游大洪水大得多;全新世以来,以3983aB.P.前后的大洪水为相对最大;公元1870年大洪水为3000aB.P.以来最大洪水;近百年来的实测洪水以公元1981年洪水为最大。 相似文献
39.
The morphology of the horn-core structure and section shape of the Bos galerianus type specimen, as well as the general anatomy of the frontal and occipital areas of the skull, suggest that the skull is better attributed to the Indian genus Hemibos. This finding contributes to our understanding of faunal dispersal patterns into Europe at the Early–Middle Pleistocene transition. 相似文献
40.
The global climate changings at the end of Pleistocene led to extinction of the typical representatives of Mammoth fauna–mammoth, woolly rhinoceros, wild horse, bison, muskox, cave lion, etc.–on the huge territories of Northern Eurasia. Undoubtedly the Mammoth fauna underwent pressure from the Upper Paleolithic Man, whose hunting activity also could play the role in decreasing the number of mammoths and other representatives of megafauna (large mammals). Archaeological data testify that the typical representatives of Mammoth fauna were the Man's hunting objects only till the end of the Pleistocene. Their bone remains are not usually found on the settlements of Mesolithic Man. Formerly it was supposed that the megafauna of ‘Mammoth complex’ was extinct by the beginning of Holocene. Nevertheless the latest data testify that the global extinction of the Mammoth fauna was sufficiently delayed in the north of Eastern Siberia. In the 1990s some radiocarbon data testified that the mammoths on the Wrangel Island existed for a long time during the Holocene from 8000 till 3700 y. BP. The present radiocarbon data show that wild horses inhabited the north of Eastern Siberia (the lower stream of the Enissey river, the Novosibirskie Islands, the East Siberian sea-shore) 3000–2000 y. BP. Musk-oxen lived on the Taimyr Peninsula and the Lena River delta about 3000 y. BP. Some bison remains from Eastern Siberia belong to the Holocene. The following circumstances could promote the process of preservation of the Mammoth fauna representatives. The cool and dry climate of this region promotes the maintenance of steppe associations – habitats of those mammals. The Late Paleolithic and Mesolithic settlements are not found in the Arctic zone of Eastern Siberia from the Taimyr Peninsula to a lower stream of the Yana River; they are very rare in the basins of the Indigirka and Kolyma Rivers. So, the small number of the Stone Age hunting tribes on the North of Eastern Siberia was another factor in the long-term preservation of some Mammoth fauna representatives. 相似文献