The Sedimentary Characteristics of the Middle-Upper Devonian Tempestite in Guilin,Guangxi and Its Geological Implications

The Middle-Upper Devonian in Guilin,Guangxi is mainly composed of carbonate rocks,several storm deposits developed in the layers.The storm sedimentary characteristics include bottom surface erosional structures,radial fabric,hummocky cross bedding,graded bedding,parallel bedding,massive bedding.The storm deposits mainly consist of five types of sedimentary units: A—massive bedding section,flat flake calcirudite with the massive bedding;B—graded bedding section,composed of calcirudite and calcarenite with graded bedding;C—hummocky cross bedding section,calcarenite with hummocky cross bedding;D—parallel bedding section,calcarenite with parallel bedding(equivalent to the B—section of bouma sequence);E—homogeneous bedding section,micrite with homogeneous bedding.The lithofacies above represent respectively deposits of storm eddy(A),deposits of storm turbidity(B),deposits of storm wave(C),deposits of storm turbidity(D),rapid suspended sediment in the late stage of storm(E).These units can be composed into different storm sedimentary sequence.The discovery of the storm deposits shows that Guilin,Guangxi should be located in the low-latitude situation during Devonian.The sediments are of great significance to explain the palaeogeography,palaeoclimate and paleoceanography of South China in the Middle-Late Devonian