Search

Ice margin remains are of great significance for reconstructing climatic conditions in certain areas and time periods and in delineating permafrost boundaries. In the middle and upper reaches of the Qingshui River in Ningxia (36°22′5"N~36°25′53"N), a group of ice margin remnants of the highest glacial period of the last glacial period were found, including ancient ice wedges and thaw folds. Among them, 4 ancient ice wedges were found in the section of Tangbao Village, which were wedge-shaped in shape, wide above and narrow below; The wedge wall is not straight, and the fissures formed before the collapse of the strata around the wedge; The wedge is filled with fragments of the surrounding formation and brownish-red silt. Two layers of continuous thaw folds were found in the section of Sanchahe Village, and the axial surface of the folds tended to be productionally chaotic and had no uniform orientation; There is no significant thickening or thinning of the fold shaft, no interlayer sliding occurs in the wing part, and the top of the fold layer is not developed and truncated; Interlayer folds are not developed interstitial backflush or positive rupture. Dating and measuring according to photoreflection14C dating results showed that paleogyne wedges formed at 14.06-11.45 ka B.P. and thaw folds formed at 13 500-11 570 a B.P. Affected by the Neo-Nymph event, the Qingshui River Basin developed a large area of permafrost at the peak of the last glacial period, with a distribution range of at least 36°22′5"N south. Since the last glacial period of northern China, the western section of the southern boundary of the permafrost can be pushed southward at least about 52′ (radial distance of about 97 km). This finding provides new evidence for the demarcation of the southern boundary of permafrost in northern China during the last glacial period [ABSTRACT FROM AUTHOR]

To reveal the historical dynamics of the population and existing genetic structure, maternal chloroplast DNA fragments(psbA-trnH, psbI-psbK and psbJ-petA)were used to study the phylogeography of Prinsepia uniflora, a kind of endemic plant distributed in the Loess Plateau. The results were as follows:(1)Total genetic diversity of P. uniflora was high(HT = 0.796), but genetic diversity within species was low(HS= 0.276);(2)The molecular variation analysis(AMOVA)showed that there was a high genetic differentiation within P. uniflora(FST = 0.674), and the genetic variation was mainly between populations(67.4%);(3)Mismatch analysis and MaxEnt based ecological niche simulation results in different historical periods showed that although the core suitable range of P. uniflora did not change much, population still expanded to some extent after the end of the Last Glacial Maximum(LGM). Our study indicated that, like most of the plant groups distributed in the northern regions of China, P. uniflora probably responded to the Quaternary climatic fluctuations by taking refuge nearby or in situ during the glacial period and locally recolonizing in following post-glacial period. [ABSTRACT FROM AUTHOR]

Based on the authors’ study on the original-define ‘Xingmincun Formation of Sinian System’， the characteristics of the glacial period environment were found in the fine grain quartz sandstone in the bottom of Zhoujiawaizi section of Xingmincun Formation， such as ice-rafting dropstone and fine laminary structure. In the bottom and upper part of Zhoujiawaizi section there are ice crystal impression and hailstone traces and other moraine traces. The Wangjiatanzi shale section of the original-define Xingmincun Formation belongs to the shallow sea facies open shelf subfacies sedimentary environment， producing different species of the medusa-like fossil which belong to the Sinian system. The structure of the medusa-like fossils produced in this layer is simple and small and the formation time should be earlier than that of Ediacaran. The Gandaozi limestone section of Xingmincun Formation belongs to the internal carbonate deposit. In view of the above research results， the authors consider that the sedimentary environment of the Zhoujiawzi sandstone， Wangjiatanzi shale and Gandaozi limestone of the original-define Xingmincun Formation is obviously different. It is necessary for original division of Xinmincun Formation to be disintegrated and divided into Zhoujiawaizi Formation， the Wangjiatanzi Formation and the Gandaozi Formation in the upper series of the Nanhua System. It is beneficial to the comparison and study of lithostratigraphy units in the late Neoproterozoic in China. [ABSTRACT FROM AUTHOR]