Armoured mud balls as a result of ephemeral fluvial flood in a humid climate:Modern example from Guizhou Province,South China  

作　　者：Gerhard H.Bachmann 

机构地区：[1]Martin-Luther-Universit?t,Institut für Geowissenschaften,Von-Seckendorff-Platz 3,D-06120 Halle (Saale),Halle (Saale),Germany

出　　处：《Journal of Palaeogeography》2014年第4期410-418,共9页古地理学报（英文版）

摘　　要：Armoured mud balls were observed after rainfall and a short flood in the otherwise dry Xiaohe （small river） valley of Guanling County, Guizhou Province, South China, approximately 30 km southwest of Guanling City. Armoured mud balls are most common in semiarid climates, but rather unusual in a humid climate as in Guizhou. A number of well-rounded mud balls, 2-20 cm in diameter, were found lying on the gravel of the Xiaohe gully floor. The mud balls consist of sticky, light brown and slightly mottled clay without carbonate content. The surfaces of the mud balls were studded with rims of sandor gravel-size limestone clasts, col- lected during bedload transport, as is typical for armoured mud balls. The mud balls originated from alluvial mudstone deposits of the valley floor and cliff that are most likely derived from the weathering and karstification of bedrock limestones. Such mudstones seem to be especially well suited for forming armoured mud balls. As flood events are rather common in the area, the formation of armoured mud balls should be very frequent in the Xiaohe valley and similar valleys nearby, giving the possibility for further and more detailed studies. To the best of our knowledge this is the first description of armoured mud balls in China.Armoured mud balls were observed after rainfall and a short flood in the otherwise dry Xiaohe （small river） valley of Guanling County, Guizhou Province, South China, approximately 30 km southwest of Guanling City. Armoured mud balls are most common in semiarid climates, but rather unusual in a humid climate as in Guizhou. A number of well-rounded mud balls, 2-20 cm in diameter, were found lying on the gravel of the Xiaohe gully floor. The mud balls consist of sticky, light brown and slightly mottled clay without carbonate content. The surfaces of the mud balls were studded with rims of sandor gravel-size limestone clasts, col- lected during bedload transport, as is typical for armoured mud balls. The mud balls originated from alluvial mudstone deposits of the valley floor and cliff that are most likely derived from the weathering and karstification of bedrock limestones. Such mudstones seem to be especially well suited for forming armoured mud balls. As flood events are rather common in the area, the formation of armoured mud balls should be very frequent in the Xiaohe valley and similar valleys nearby, giving the possibility for further and more detailed studies. To the best of our knowledge this is the first description of armoured mud balls in China.

关 键 词：armoured mud balls FLUVIAL alluvial MUDSTONES humid climate Guizhou South China 

分 类 号：P53[天文地球—古生物学与地层学]